Create an Account  |   Log In

View All »Matching Part Numbers


Your Shopping Cart is Empty
         

Single Mode Fiber


  • Operating Wavelengths from 320 nm to 2.3 µm
  • Shipped from Stock with No Minimum Order
  • Patch Cables Available for All Fibers
  • Ø80 µm or Ø125 µm Cladding Available

Typical Output Beam Profile from a Single Mode Fiber

Some Fibers are Available with
a Ø900 µm Hytrel Jacket

Single Mode Fiber Cross Section

Related Items


Please Wait

Single Mode Fiber: 320 to 430 nm

Stock Patch Cables Available with This Fiber
SM300 Fiber
Item # Prefix Connectors Length
P1-305A-FC FC/PC to FC/PC 1 or 2 m
P3-305A-FC FC/APC to FC/APC 1 m
P5-305A-PCAPC FC/PC to FC/APC 1 m
P1-305AR-2 AR-Coated (300 - 510 nm) FC/PC to Uncoated FC/PC 2 m
P5-305AR-2 AR-Coated (300 - 510 nm) FC/PC to Uncoated FC/APC 2 m
P4-305AR-2 AR-Coated (300 - 510 nm) FC/APC to Uncoated FC/PC 2 m
P3-305AR-2 AR-Coated (300 - 510 nm) FC/APC to Uncoated FC/APC 2 m
P1-305P-FC FC/PC to FC/PC (Low Insertion Loss) 1 or 2 m
P3-305P-FC FC/APC to FC/APC (Low Insertion Loss) 1 or 2 m
P5-305P-PCAPC-1 FC/PC to FC/APC (Low Insertion Loss) 1 m

Custom cables are also available. Click here for details.

Custom Patch Cables
Stock Single Mode Patch Cables

Features

  • Single Mode Transmission from 320 to 430 nm
  • Dual Acrylate Coating
  • Shipped from Stock
  • No Minimum Purchase Required

Thorlabs' SM300 fiber consists of an undoped, pure silica core surrounded by a depressed, fluorine-doped cladding. Since these fibers do not contain germania (GeO2), which causes electronic defects and color centers associated with the Ge-O bond, the primary cause of photodarkening is greatly reduced. As a result, power handling in the blue region is increased from several milliwats to several watts. The transmission-limiting effects caused by other nonlinearities (e.g., stimulated scattering) or even thermal damage are also increased over those of a conventional silica fiber doped with germanium. In the UV region, the SM300 will still exhibit some photodarkening, but will have superior performance compared to conventional fibers.

Item #Operating WavelengthMode Field DiameteraCladdingCoatingCut-Off Wavelength
SM300 320 - 430 nm 2.0 - 2.4 µm @ 350 nm 125 ± 1 µm 245 ± 15 µm ≤310 nm
Item #Short-Term Bend RadiusLong-Term Bend RadiusAttenuation (Max)Proof Test LevelNACore IndexbCladding Indexb
SM300 ≥10 mm ≥30 mm ≤70 dB/km @ 350 nm 1% (100 kpsi)
2% (200 kpsi)
3% (300 kpsi)
0.12 - 0.14 320 nm: 1.48770
375 nm: 1.47809
430 nm: 1.47214
320 nm: 1.48276
375 nm: 1.47315
430 nm: 1.46720
  • MFD is a nominal, calculated value, estimated at the operating wavelength(s) using a typical value of NA & cut-off wavelength. Please see the MFD Definition tab for details.
  • The indices provided are for an NA of 0.12.

Definition of the Mode Field Diameter

The mode field diameter (MFD) is one measure of the beam size of light propagating in a single mode fiber. It is a function of wavelength, core radius, and the refractive indices of the core and cladding. While much of the light in an optical fiber is trapped within the fiber core, a small fraction propagates in the cladding. For a Gaussian power distribution, the MFD is the diameter where the optical power is reduced to 1/e2 from its peak level.

Measurement of MFD
The measurement of MFD is accomplished by the Variable Aperture Method in the Far Field (VAMFF). An aperture is placed in the far field of the fiber output, and the intensity is measured. As successively smaller apertures are placed in the beam, the intensity levels are measured for each aperture; the data can then be plotted as power vs. the sine of the aperture half-angle (or the numerical aperture).

The MFD is then determined using Petermann's second definition, which is a mathematical model that does not assume a specific shape of power distribution. The MFD in the near field can be determined from this far-field measurement using the Hankel Transform.

Laser-Induced Damage in Silica Optical Fibers

The following tutorial details damage mechanisms relevant to unterminated (bare) fiber, terminated optical fiber, and other fiber components from laser light sources. These mechanisms include damage that occurs at the air / glass interface (when free-space coupling or when using connectors) and in the optical fiber itself. A fiber component, such as a bare fiber, patch cable, or fused coupler, may have multiple potential avenues for damage (e.g., connectors, fiber end faces, and the device itself). The maximum power that a fiber can handle will always be limited by the lowest limit of any of these damage mechanisms.

While the damage threshold can be estimated using scaling relations and general rules, absolute damage thresholds in optical fibers are very application dependent and user specific. Users can use this guide to estimate a safe power level that minimizes the risk of damage. Following all appropriate preparation and handling guidelines, users should be able to operate a fiber component up to the specified maximum power level; if no maximum is specified for a component, users should abide by the "practical safe level" described below for safe operation of the component. Factors that can reduce power handling and cause damage to a fiber component include, but are not limited to, misalignment during fiber coupling, contamination of the fiber end face, or imperfections in the fiber itself. For further discussion about an optical fiber’s power handling abilities for a specific application, please contact Thorlabs’ Tech Support.

Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Undamaged Fiber End
Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Damaged Fiber End

Damage at the Air / Glass Interface

There are several potential damage mechanisms that can occur at the air / glass interface. Light is incident on this interface when free-space coupling or when two fibers are mated using optical connectors. High-intensity light can damage the end face leading to reduced power handling and permanent damage to the fiber. For fibers terminated with optical connectors where the connectors are fixed to the fiber ends using epoxy, the heat generated by high-intensity light can burn the epoxy and leave residues on the fiber facet directly in the beam path.

Estimated Optical Power Densities on Air / Glass Interfacea
Type Theoretical Damage Thresholdb Practical Safe Levelc
CW
(Average Power)
~1 MW/cm2 ~250 kW/cm2
10 ns Pulsed
(Peak Power)
~5 GW/cm2 ~1 GW/cm2
  • All values are specified for unterminated (bare) silica fiber and apply for free space coupling into a clean fiber end face.
  • This is an estimated maximum power density that can be incident on a fiber end face without risking damage. Verification of the performance and reliability of fiber components in the system before operating at high power must be done by the user, as it is highly system dependent.
  • This is the estimated safe optical power density that can be incident on a fiber end face without damaging the fiber under most operating conditions.

Damage Mechanisms on the Bare Fiber End Face

Damage mechanisms on a fiber end face can be modeled similarly to bulk optics, and industry-standard damage thresholds for UV Fused Silica substrates can be applied to silica-based fiber. However, unlike bulk optics, the relevant surface areas and beam diameters involved at the air / glass interface of an optical fiber are very small, particularly for coupling into single mode (SM) fiber. therefore, for a given power density, the power incident on the fiber needs to be lower for a smaller beam diameter.

The table to the right lists two thresholds for optical power densities: a theoretical damage threshold and a "practical safe level". In general, the theoretical damage threshold represents the estimated maximum power density that can be incident on the fiber end face without risking damage with very good fiber end face and coupling conditions. The "practical safe level" power density represents minimal risk of fiber damage. Operating a fiber or component beyond the practical safe level is possible, but users must follow the appropriate handling instructions and verify performance at low powers prior to use.

Calculating the Effective Area for Single Mode and Multimode Fibers
The effective area for single mode (SM) fiber is defined by the mode field diameter (MFD), which is the cross-sectional area through which light propagates in the fiber; this area includes the fiber core and also a portion of the cladding. To achieve good efficiency when coupling into a single mode fiber, the diameter of the input beam must match the MFD of the fiber.

As an example, SM400 single mode fiber has a mode field diameter (MFD) of ~Ø3 µm operating at 400 nm, while the MFD for SMF-28 Ultra single mode fiber operating at 1550 nm is Ø10.5 µm. The effective area for these fibers can be calculated as follows:

SM400 Fiber: Area = Pi x (MFD/2)2 = Pi x (1.5 µm)2 = 7.07 µm= 7.07 x 10-8 cm2

 SMF-28 Ultra Fiber: Area = Pi x (MFD/2)2 = Pi x (5.25 µm)2 = 86.6 µm= 8.66 x 10-7 cm2

To estimate the power level that a fiber facet can handle, the power density is multiplied by the effective area. Please note that this calculation assumes a uniform intensity profile, but most laser beams exhibit a Gaussian-like shape within single mode fiber, resulting in a higher power density at the center of the beam compared to the edges. Therefore, these calculations will slightly overestimate the power corresponding to the damage threshold or the practical safe level. Using the estimated power densities assuming a CW light source, we can determine the corresponding power levels as:

SM400 Fiber: 7.07 x 10-8 cm2 x 1 MW/cm2 = 7.1 x 10-8 MW = 71 mW (Theoretical Damage Threshold)
     7.07 x 10-8 cm2 x 250 kW/cm2 = 1.8 x 10-5 kW = 18 mW (Practical Safe Level)

SMF-28 Ultra Fiber: 8.66 x 10-7 cm2 x 1 MW/cm2 = 8.7 x 10-7 MW = 870 mW (Theoretical Damage Threshold)
           8.66 x 10-7 cm2 x 250 kW/cm2 = 2.1 x 10-4 kW = 210 mW (Practical Safe Level)

The effective area of a multimode (MM) fiber is defined by the core diameter, which is typically far larger than the MFD of an SM fiber. For optimal coupling, Thorlabs recommends focusing a beam to a spot roughly 70 - 80% of the core diameter. The larger effective area of MM fibers lowers the power density on the fiber end face, allowing higher optical powers (typically on the order of kilowatts) to be coupled into multimode fiber without damage.

Damage Mechanisms Related to Ferrule / Connector Termination


Click to Enlarge
Plot showing approximate power handling levels for single mode silica optical fiber with a termination. Each line shows the estimated power level due to a specific damage mechanism. The maximum power handling is limited by the lowest power level from all relevant damage mechanisms (indicated by a solid line).

Fibers terminated with optical connectors have additional power handling considerations. Fiber is typically terminated using epoxy to bond the fiber to a ceramic or steel ferrule. When light is coupled into the fiber through a connector, light that does not enter the core and propagate down the fiber is scattered into the outer layers of the fiber, into the ferrule, and the epoxy used to hold the fiber in the ferrule. If the light is intense enough, it can burn the epoxy, causing it to vaporize and deposit a residue on the face of the connector. This results in localized absorption sites on the fiber end face that reduce coupling efficiency and increase scattering, causing further damage.

For several reasons, epoxy-related damage is dependent on the wavelength. In general, light scatters more strongly at short wavelengths than at longer wavelengths. Misalignment when coupling is also more likely due to the small MFD of short-wavelength SM fiber that also produces more scattered light.

To minimize the risk of burning the epoxy, fiber connectors can be constructed to have an epoxy-free air gap between the optical fiber and ferrule near the fiber end face. Our high-power multimode fiber patch cables use connectors with this design feature.

Determining Power Handling with Multiple Damage Mechanisms

When fiber cables or components have multiple avenues for damage (e.g., fiber patch cables), the maximum power handling is always limited by the lowest damage threshold that is relevant to the fiber component.

As an illustrative example, the graph to the right shows an estimate of the power handling limitations of a single mode fiber patch cable due to damage to the fiber end face and damage via an optical connector. The total power handling of a terminated fiber at a given wavelength is limited by the lower of the two limitations at any given wavelength (indicated by the solid lines). A single mode fiber operating at around 488 nm is primarily limited by damage to the fiber end face (blue solid line), but fibers operating at 1550 nm are limited by damage to the optical connector (red solid line).

In the case of a multimode fiber, the effective mode area is defined by the core diameter, which is larger than the effective mode area for SM fiber. This results in a lower power density on the fiber end face and allows higher optical powers (on the order of kilowatts) to be coupled into the fiber without damage (not shown in graph). However, the damage limit of the ferrule / connector termination remains unchanged and as a result, the maximum power handling for a multimode fiber is limited by the ferrule and connector termination. 

Please note that these are rough estimates of power levels where damage is very unlikely with proper handling and alignment procedures. It is worth noting that optical fibers are frequently used at power levels above those described here. However, these applications typically require expert users and testing at lower powers first to minimize risk of damage. Even still, optical fiber components should be considered a consumable lab supply if used at high power levels.

Intrinsic Damage Threshold

In addition to damage mechanisms at the air / glass interface, optical fibers also display power handling limitations due to damage mechanisms within the optical fiber itself. These limitations will affect all fiber components as they are intrinsic to the fiber itself. Two categories of damage within the fiber are damage from bend losses and damage from photodarkening. 

Bend Losses
Bend losses occur when a fiber is bent to a point where light traveling in the core is incident on the core/cladding interface at an angle higher than the critical angle, making total internal reflection impossible. Under these circumstances, light escapes the fiber, often in a localized area. The light escaping the fiber typically has a high power density, which burns the fiber coating as well as any surrounding furcation tubing.

A special category of optical fiber, called double-clad fiber, can reduce the risk of bend-loss damage by allowing the fiber’s cladding (2nd layer) to also function as a waveguide in addition to the core. By making the critical angle of the cladding/coating interface higher than the critical angle of the core/clad interface, light that escapes the core is loosely confined within the cladding. It will then leak out over a distance of centimeters or meters instead of at one localized spot within the fiber, minimizing the risk of damage. Thorlabs manufactures and sells 0.22 NA double-clad multimode fiber, which boasts very high, megawatt range power handling.

Photodarkening
A second damage mechanism, called photodarkening or solarization, can occur in fibers used with ultraviolet or short-wavelength visible light, particularly those with germanium-doped cores. Fibers used at these wavelengths will experience increased attenuation over time. The mechanism that causes photodarkening is largely unknown, but several fiber designs have been developed to mitigate it. For example, fibers with a very low hydroxyl ion (OH) content have been found to resist photodarkening and using other dopants, such as fluorine, can also reduce photodarkening.

Even with the above strategies in place, all fibers eventually experience photodarkening when used with UV or short-wavelength light, and thus, fibers used at these wavelengths should be considered consumables.

Preparation and Handling of Optical Fibers

General Cleaning and Operation Guidelines
These general cleaning and operation guidelines are recommended for all fiber optic products. Users should still follow specific guidelines for an individual product as outlined in the support documentation or manual. Damage threshold calculations only apply when all appropriate cleaning and handling procedures are followed.

  1. All light sources should be turned off prior to installing or integrating optical fibers (terminated or bare). This ensures that focused beams of light are not incident on fragile parts of the connector or fiber, which can possibly cause damage.

  2. The power-handling capability of an optical fiber is directly linked to the quality of the fiber/connector end face. Always inspect the fiber end prior to connecting the fiber to an optical system. The fiber end face should be clean and clear of dirt and other contaminants that can cause scattering of coupled light. Bare fiber should be cleaved prior to use and users should inspect the fiber end to ensure a good quality cleave is achieved.

  3. If an optical fiber is to be spliced into the optical system, users should first verify that the splice is of good quality at a low optical power prior to high-power use. Poor splice quality may increase light scattering at the splice interface, which can be a source of fiber damage.

  4. Users should use low power when aligning the system and optimizing coupling; this minimizes exposure of other parts of the fiber (other than the core) to light. Damage from scattered light can occur if a high power beam is focused on the cladding, coating, or connector.

Tips for Using Fiber at Higher Optical Power
Optical fibers and fiber components should generally be operated within safe power level limits, but under ideal conditions (very good optical alignment and very clean optical end faces), the power handling of a fiber component may be increased. Users must verify the performance and stability of a fiber component within their system prior to increasing input or output power and follow all necessary safety and operation instructions. The tips below are useful suggestions when considering increasing optical power in an optical fiber or component.

  1. Splicing a fiber component into a system using a fiber splicer can increase power handling as it minimizes possibility of air/fiber interface damage. Users should follow all appropriate guidelines to prepare and make a high-quality fiber splice. Poor splices can lead to scattering or regions of highly localized heat at the splice interface that can damage the fiber.

  2. After connecting the fiber or component, the system should be tested and aligned using a light source at low power. The system power can be ramped up slowly to the desired output power while periodically verifying all components are properly aligned and that coupling efficiency is not changing with respect to optical launch power.

  3. Bend losses that result from sharply bending a fiber can cause light to leak from the fiber in the stressed area. When operating at high power, the localized heating that can occur when a large amount of light escapes a small localized area (the stressed region) can damage the fiber. Avoid disturbing or accidently bending fibers during operation to minimize bend losses.

  4. Users should always choose the appropriate optical fiber for a given application. For example, large-mode-area fibers are a good alternative to standard single mode fibers in high-power applications as they provide good beam quality with a larger MFD, decreasing the power density on the air/fiber interface.

  5. Step-index silica single mode fibers are normally not used for ultraviolet light or high-peak-power pulsed applications due to the high spatial power densities associated with these applications.


Please Give Us Your Feedback
 
Email Feedback On
(Optional)
Contact Me:
Your email address will NOT be displayed.
 
 
Please type the following key into the field to submit this form:
Click Here if you can not read the security code.
This code is to prevent automated spamming of our site
Thank you for your understanding.
  
 
Would this product be useful to you?   Little Use  1234Very Useful

Enter Comments Below:
 
Characters remaining  8000   
Posted Comments:
Poster:yeongdae
Posted Date:2017-08-26 17:43:36.093
Hi. I was looking at 'Specs' and 'MFD Definition' tab of [Single Mode Fiber: 320 to 430 nm] page. There, it says your 320 - 430 nm fiber's Mode Field Diameter is 2.0~2.4 microns. My measurement on this fiber actually gives twice that value. My hypothesis is that MFD definition is sometimes confusing, as this value is also 2*omega_0 where omega_0 is "beam waist" following the definition of Wikipedia's [Gaussian beam] page. Maybe what you wrote as Mode Field Diameter is actaully omega_0 value?? Can you check this and give me a feedback, as I also want to make sure that my measurements were in fact correct??
Poster:tfrisch
Posted Date:2017-09-14 03:53:23.0
Hello, thank you for contacting Thorlabs. I will reach out to you directly to compare our calculations. I'd be interested to see if you use a model that deviates from the Variable Aperture Method in the Far Field.
Poster:vivien.loo
Posted Date:2017-07-06 13:28:56.17
Hi, SM300 has a pure undoped silica core, is it the same for SM600 and 630HP?
Poster:nbayconich
Posted Date:2017-08-08 09:56:51.0
Thank you for contacting Thorlabs. The SM600 and 630HP fibers have GeO2 doped cores. I will contact you directly with more information.
Poster:goodwi63
Posted Date:2017-01-26 16:07:49.89
I would like to know the core diameter for the SM300, and if it is not the smallest core diameter, which of your products has the smallest core diameter.
Poster:pbui
Posted Date:2017-01-30 04:23:11.0
Thank you for your inquiry. We will contact you directly to discuss your application requirements and recommend the appropriate fiber.
Poster:soshenko.v
Posted Date:2016-02-02 11:03:16.203
Hello, can you give some data for non-bridging oxygen centers in this fiber and its intrinsic fluorescence? Comparing to SM600, is fluorescence higher or lower? Is this fiber somehow related (Thorlabs buys it from them or vice versa) to Nufern 630HP fiber?
Poster:besembeson
Posted Date:2016-02-04 03:19:11.0
Response from Bweh at Thorlabs USA: Thanks for contacting Thorlabs. We don't have such data at the moment for the SM300, and we don't have a fluorescence comparison with the SM600 either. Our 630HP has the same specifications as the Nufern 630HP.
Poster:mchen
Posted Date:2014-07-09 10:56:22.61
Hi, Can you please tell me what is the dispersion of SM2000 fiber? thanks, Mike
Poster:jlow
Posted Date:2014-08-07 10:17:45.0
Response from Jeremy at Thorlabs: The dispersion is estimated to be around 47ps/(nm*km) at 2000nm.
Poster:lokirune
Posted Date:2014-05-21 14:45:27.98
HI. I was using the SM450 and 460HP, and it seems to burn easily. Is there any data sheet for damage threshold for those fiber? Also, I used it before and find that it much easier to burn with pulse laser. It there any specific reason for that?
Poster:pbui
Posted Date:2014-06-02 09:46:36.0
There are no data sheets for damage threshold available, but it's possible to apply industry-standard damage thresholds for UV Fused Silica substrates to silica-based fibers. The surface areas and beam diameters involved at the air to glass interface are extremely small compared to bulk optics, especially with single mode (SM) fiber, and this results in very small damage thresholds. Assuming you're launching into bare fiber (no connectors), 250 kW/cm^2 is a practical value for Maximum Power Density for CW lasers, while for a 10 ns Pulsed (peak power) laser, the max may be around 1 GW/cm^2. We will contact you directly to find out more about your setup and to provide further details.
Poster:helmofon
Posted Date:2013-12-15 14:18:47.37
Dear Sir/Madam I will be very grateful for the information about refractive index of core and clad of SMF - 28 @1550nm. Thank You, Maciej
Poster:jlow
Posted Date:2013-12-17 08:50:38.0
Response from Jeremy at Thorlabs: The refractive index for the core and clad is around 1.4682 and 1.4615 respectively for SMF-28e+ at 1550nm.
Poster:akselrod
Posted Date:2013-03-12 18:02:09.78
I would like to know the dispersion of this fiber at around 400 nm. Can you pleas let me know this value? Thanks! Gleb
Poster:jlow
Posted Date:2013-04-11 15:40:00.0
Response from Jeremy at Thorlabs: Based on the generally used formula for waveguide dispersion and chromatic dispersion, the estimated dispersion for SM300 is on the order of -23 ps/(km-nm) at 400nm. That value can change depending on the actual numerical aperture and the cut-off wavelength of each spool of fiber.
Poster:bdada
Posted Date:2012-06-05 19:30:00.0
Response from Buki at Thorlabs to Alfred: Thank you for participating in our feedback forum. Below is the refractive index of 780HP at 780nm: Core = 1.4598 Clad = 1.4537 Please contact TechSupport@thorlabs.com if you have any questions.
Poster:
Posted Date:2012-06-05 04:25:46.0
Dear Sir or Madame, I want to know the refractive index of 780HP, then I will determine how long the fiber I will order. Thank you in advance. Alfred
Poster:tcohen
Posted Date:2012-03-01 14:33:00.0
Response from Tim at Thorlabs: Thank you for your feedback. The S405-HP has a core index of 1.46958 and clad index of 1.46428 measured at 405nm. The MFD @ 460nm is 3.2 +/- .5 um. Please use these as references but note that they are approximate and may vary from lot to lot.
Poster:marko.vranicar
Posted Date:2012-02-29 19:04:22.0
Dear Sir Or Madame, Recently, we purchased the S405-HP fiber. We need to know the cladding and core refractive indices as well as the core radius at 473nm that I cannot find in specs. I thank you in advance for your answer and assistance. Best regards, Marko
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
SM300 Support Documentation
SM300Customer Inspired!Single Mode Optical Fiber, 320 - 430 nm, Ø125 µm Cladding
$17.40
Per Meter
Volume Pricing
Today

Single Mode Fiber: 400 to 680 nm

Stock Patch Cables Available with These Fibers
SM400 Fiber
Item # Prefix Connectors Length
P1-405B-FC FC/PC to FC/PC 1, 2, or 5 m
P3-405B-FC FC/APC to FC/APC 1, 2, or 5 m
P5-405B-PCAPC FC/PC to FC/APC 1 m
P2-405B-PCSMA FC/PC to SMA 1 m
P1-405AR-2 AR-Coated (400 - 700 nm) FC/PC to Uncoated FC/PC 2 m
P5-405AR-2 AR-Coated (400 - 700 nm) FC/PC to Uncoated FC/APC 2 m
P4-405AR-2 AR-Coated (400 - 700 nm) FC/APC to Uncoated FC/PC 2 m
P3-405AR-2 AR-Coated (400 - 700 nm) FC/APC to Uncoated FC/APC 2 m
P1-405P-FC FC/PC to FC/PC (Low Insertion Loss) 1, 2, or 5 m
P3-405P-FC FC/APC to FC/APC (Low Insertion Loss) 1, 2, or 5 m
P5-405P-PCAPC-1 FC/PC to FC/APC (Low Insertion Loss) 1 m
SM450 Fiber
Item # Prefix Connectors Length
P1-460B-FC FC/PC to FC/PC 1, 2, or 5 m
P3-460B-FC FC/APC to FC/APC 1, 2, or 5 m
P5-460B-PCAPC FC/PC to FC/APC 1 m
P2-460B-PCSMA FC/PC to SMA 1 m
P1-460AR-2 AR-Coated (400 - 700 nm) FC/PC to Uncoated FC/PC 2 m
P5-460AR-2 AR-Coated (400 - 700 nm) FC/PC to Uncoated FC/APC 2 m
P4-460AR-2 AR-Coated (400 - 700 nm) FC/APC to Uncoated FC/PC 2 m
P3-460AR-2 AR-Coated (400 - 700 nm) FC/APC to Uncoated FC/APC 2 m
P1-460P-FC FC/PC to FC/PC (Low Insertion Loss) 1, 2, or 5 m
P3-460P-FC FC/APC to FC/APC (Low Insertion Loss) 1, 2, or 5 m
P5-460P-PCAPC-1 FC/PC to FC/APC (Low Insertion Loss) 1 m

Custom cables are also available. Click here for details.

Custom Patch Cables
Stock Single Mode Patch Cables

Features

  • SM Fiber at 400 nm to 680 nm
  • Shipped from Stock
  • Acrylate Jacket
  • No Minimum Purchase Required
Item # Operating Wavelength Mode Field Diameter Cladding Coating Cut-Off Wavelength
S405-XP 400 - 680 nm 3.3 ± 0.5 µm @ 405 nm
4.6 ± 0.5 µm @ 630 nm
125.0 ± 1.0 µm 245.0 ± 15.0 µm 380 ± 20 nm
SM400 405 - 532 nm 2.5 - 3.4 µm @ 480 nm 125 ± 1 µm 245 ± 15 µm 305 - 400 nm
SM450a 488 - 633 nm 2.8 - 4.1 µmb @ 488 nm 125 ± 1.0 µm 245 ± 15 µm 350 - 470 nm
460HP 450 - 600 nm 3.5 ± 0.5 µm @ 515 nm 125 ± 1 µm 245 ± 15 µm 430 ± 20 nm
Item # Short-Term Bend Radius Long-Term Bend Radius Attenuation (Max) NA Core Index Cladding Index
S405-XP ≥6 mm ≥13 mm ≤30.0 dB/km @ 630 nm
≤30.0 dB/km @ 488 nm
0.12 Calld Calld
SM400 ≥10 mm ≥30 mm ≤50 dB/km @ 430 nm
≤30 dB/km @ 532 nm
0.12 - 0.14 405 nm: 1.47453e
467 nm: 1.46929e
532 nm: 1.46565e
405 nm: 1.46959e
467 nm: 1.46435e
532 nm: 1.46071e
SM450 ≥5 mm ≥25 mm ≤50 dB/km @ 488 nmc 0.10 - 0.14 488 nm: 1.46645f
514 nm: 1.46501f
488 nm: 1.46302f
514 nm: 1.46159f
460HP - - ≤30 dB/km @ 515 nm 0.13 Calld Calld
  • The wavelength range is the spectral region between the cutoff wavelength and the bend edge and represents the region where the fiber transmits the TEM00 mode with low attenuation. For this fiber, the bend edge wavelength is typically 200 nm longer than the cut-off wavelength.
  • MFD is a nominal, calculated value, estimated at the operating wavelength(s) using a typical value of NA & cutoff wavelength. Please see the MFD Definition tab for details.
  • Stated attenuation is a worst-case value, quoted for the shortest design wavelength.
  • Please contact our Technical Support Staff to learn more about the refractive index of this fiber, as we are not permitted to publish this information on our website.
  • The indices provided are for an NA of 0.12.
  • The indices provided are for an NA of 0.10.

Definition of the Mode Field Diameter

The mode field diameter (MFD) is one measure of the beam size of light propagating in a single mode fiber. It is a function of wavelength, core radius, and the refractive indices of the core and cladding. While much of the light in an optical fiber is trapped within the fiber core, a small fraction propagates in the cladding. For a Gaussian power distribution, the MFD is the diameter where the optical power is reduced to 1/e2 from its peak level.

Measurement of MFD
The measurement of MFD is accomplished by the Variable Aperture Method in the Far Field (VAMFF). An aperture is placed in the far field of the fiber output, and the intensity is measured. As successively smaller apertures are placed in the beam, the intensity levels are measured for each aperture; the data can then be plotted as power vs. the sine of the aperture half-angle (or the numerical aperture).

The MFD is then determined using Petermann's second definition, which is a mathematical model that does not assume a specific shape of power distribution. The MFD in the near field can be determined from this far-field measurement using the Hankel Transform.

Laser-Induced Damage in Silica Optical Fibers

The following tutorial details damage mechanisms relevant to unterminated (bare) fiber, terminated optical fiber, and other fiber components from laser light sources. These mechanisms include damage that occurs at the air / glass interface (when free-space coupling or when using connectors) and in the optical fiber itself. A fiber component, such as a bare fiber, patch cable, or fused coupler, may have multiple potential avenues for damage (e.g., connectors, fiber end faces, and the device itself). The maximum power that a fiber can handle will always be limited by the lowest limit of any of these damage mechanisms.

While the damage threshold can be estimated using scaling relations and general rules, absolute damage thresholds in optical fibers are very application dependent and user specific. Users can use this guide to estimate a safe power level that minimizes the risk of damage. Following all appropriate preparation and handling guidelines, users should be able to operate a fiber component up to the specified maximum power level; if no maximum is specified for a component, users should abide by the "practical safe level" described below for safe operation of the component. Factors that can reduce power handling and cause damage to a fiber component include, but are not limited to, misalignment during fiber coupling, contamination of the fiber end face, or imperfections in the fiber itself. For further discussion about an optical fiber’s power handling abilities for a specific application, please contact Thorlabs’ Tech Support.

Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Undamaged Fiber End
Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Damaged Fiber End

Damage at the Air / Glass Interface

There are several potential damage mechanisms that can occur at the air / glass interface. Light is incident on this interface when free-space coupling or when two fibers are mated using optical connectors. High-intensity light can damage the end face leading to reduced power handling and permanent damage to the fiber. For fibers terminated with optical connectors where the connectors are fixed to the fiber ends using epoxy, the heat generated by high-intensity light can burn the epoxy and leave residues on the fiber facet directly in the beam path.

Estimated Optical Power Densities on Air / Glass Interfacea
Type Theoretical Damage Thresholdb Practical Safe Levelc
CW
(Average Power)
~1 MW/cm2 ~250 kW/cm2
10 ns Pulsed
(Peak Power)
~5 GW/cm2 ~1 GW/cm2
  • All values are specified for unterminated (bare) silica fiber and apply for free space coupling into a clean fiber end face.
  • This is an estimated maximum power density that can be incident on a fiber end face without risking damage. Verification of the performance and reliability of fiber components in the system before operating at high power must be done by the user, as it is highly system dependent.
  • This is the estimated safe optical power density that can be incident on a fiber end face without damaging the fiber under most operating conditions.

Damage Mechanisms on the Bare Fiber End Face

Damage mechanisms on a fiber end face can be modeled similarly to bulk optics, and industry-standard damage thresholds for UV Fused Silica substrates can be applied to silica-based fiber. However, unlike bulk optics, the relevant surface areas and beam diameters involved at the air / glass interface of an optical fiber are very small, particularly for coupling into single mode (SM) fiber. therefore, for a given power density, the power incident on the fiber needs to be lower for a smaller beam diameter.

The table to the right lists two thresholds for optical power densities: a theoretical damage threshold and a "practical safe level". In general, the theoretical damage threshold represents the estimated maximum power density that can be incident on the fiber end face without risking damage with very good fiber end face and coupling conditions. The "practical safe level" power density represents minimal risk of fiber damage. Operating a fiber or component beyond the practical safe level is possible, but users must follow the appropriate handling instructions and verify performance at low powers prior to use.

Calculating the Effective Area for Single Mode and Multimode Fibers
The effective area for single mode (SM) fiber is defined by the mode field diameter (MFD), which is the cross-sectional area through which light propagates in the fiber; this area includes the fiber core and also a portion of the cladding. To achieve good efficiency when coupling into a single mode fiber, the diameter of the input beam must match the MFD of the fiber.

As an example, SM400 single mode fiber has a mode field diameter (MFD) of ~Ø3 µm operating at 400 nm, while the MFD for SMF-28 Ultra single mode fiber operating at 1550 nm is Ø10.5 µm. The effective area for these fibers can be calculated as follows:

SM400 Fiber: Area = Pi x (MFD/2)2 = Pi x (1.5 µm)2 = 7.07 µm= 7.07 x 10-8 cm2

 SMF-28 Ultra Fiber: Area = Pi x (MFD/2)2 = Pi x (5.25 µm)2 = 86.6 µm= 8.66 x 10-7 cm2

To estimate the power level that a fiber facet can handle, the power density is multiplied by the effective area. Please note that this calculation assumes a uniform intensity profile, but most laser beams exhibit a Gaussian-like shape within single mode fiber, resulting in a higher power density at the center of the beam compared to the edges. Therefore, these calculations will slightly overestimate the power corresponding to the damage threshold or the practical safe level. Using the estimated power densities assuming a CW light source, we can determine the corresponding power levels as:

SM400 Fiber: 7.07 x 10-8 cm2 x 1 MW/cm2 = 7.1 x 10-8 MW = 71 mW (Theoretical Damage Threshold)
     7.07 x 10-8 cm2 x 250 kW/cm2 = 1.8 x 10-5 kW = 18 mW (Practical Safe Level)

SMF-28 Ultra Fiber: 8.66 x 10-7 cm2 x 1 MW/cm2 = 8.7 x 10-7 MW = 870 mW (Theoretical Damage Threshold)
           8.66 x 10-7 cm2 x 250 kW/cm2 = 2.1 x 10-4 kW = 210 mW (Practical Safe Level)

The effective area of a multimode (MM) fiber is defined by the core diameter, which is typically far larger than the MFD of an SM fiber. For optimal coupling, Thorlabs recommends focusing a beam to a spot roughly 70 - 80% of the core diameter. The larger effective area of MM fibers lowers the power density on the fiber end face, allowing higher optical powers (typically on the order of kilowatts) to be coupled into multimode fiber without damage.

Damage Mechanisms Related to Ferrule / Connector Termination


Click to Enlarge
Plot showing approximate power handling levels for single mode silica optical fiber with a termination. Each line shows the estimated power level due to a specific damage mechanism. The maximum power handling is limited by the lowest power level from all relevant damage mechanisms (indicated by a solid line).

Fibers terminated with optical connectors have additional power handling considerations. Fiber is typically terminated using epoxy to bond the fiber to a ceramic or steel ferrule. When light is coupled into the fiber through a connector, light that does not enter the core and propagate down the fiber is scattered into the outer layers of the fiber, into the ferrule, and the epoxy used to hold the fiber in the ferrule. If the light is intense enough, it can burn the epoxy, causing it to vaporize and deposit a residue on the face of the connector. This results in localized absorption sites on the fiber end face that reduce coupling efficiency and increase scattering, causing further damage.

For several reasons, epoxy-related damage is dependent on the wavelength. In general, light scatters more strongly at short wavelengths than at longer wavelengths. Misalignment when coupling is also more likely due to the small MFD of short-wavelength SM fiber that also produces more scattered light.

To minimize the risk of burning the epoxy, fiber connectors can be constructed to have an epoxy-free air gap between the optical fiber and ferrule near the fiber end face. Our high-power multimode fiber patch cables use connectors with this design feature.

Determining Power Handling with Multiple Damage Mechanisms

When fiber cables or components have multiple avenues for damage (e.g., fiber patch cables), the maximum power handling is always limited by the lowest damage threshold that is relevant to the fiber component.

As an illustrative example, the graph to the right shows an estimate of the power handling limitations of a single mode fiber patch cable due to damage to the fiber end face and damage via an optical connector. The total power handling of a terminated fiber at a given wavelength is limited by the lower of the two limitations at any given wavelength (indicated by the solid lines). A single mode fiber operating at around 488 nm is primarily limited by damage to the fiber end face (blue solid line), but fibers operating at 1550 nm are limited by damage to the optical connector (red solid line).

In the case of a multimode fiber, the effective mode area is defined by the core diameter, which is larger than the effective mode area for SM fiber. This results in a lower power density on the fiber end face and allows higher optical powers (on the order of kilowatts) to be coupled into the fiber without damage (not shown in graph). However, the damage limit of the ferrule / connector termination remains unchanged and as a result, the maximum power handling for a multimode fiber is limited by the ferrule and connector termination. 

Please note that these are rough estimates of power levels where damage is very unlikely with proper handling and alignment procedures. It is worth noting that optical fibers are frequently used at power levels above those described here. However, these applications typically require expert users and testing at lower powers first to minimize risk of damage. Even still, optical fiber components should be considered a consumable lab supply if used at high power levels.

Intrinsic Damage Threshold

In addition to damage mechanisms at the air / glass interface, optical fibers also display power handling limitations due to damage mechanisms within the optical fiber itself. These limitations will affect all fiber components as they are intrinsic to the fiber itself. Two categories of damage within the fiber are damage from bend losses and damage from photodarkening. 

Bend Losses
Bend losses occur when a fiber is bent to a point where light traveling in the core is incident on the core/cladding interface at an angle higher than the critical angle, making total internal reflection impossible. Under these circumstances, light escapes the fiber, often in a localized area. The light escaping the fiber typically has a high power density, which burns the fiber coating as well as any surrounding furcation tubing.

A special category of optical fiber, called double-clad fiber, can reduce the risk of bend-loss damage by allowing the fiber’s cladding (2nd layer) to also function as a waveguide in addition to the core. By making the critical angle of the cladding/coating interface higher than the critical angle of the core/clad interface, light that escapes the core is loosely confined within the cladding. It will then leak out over a distance of centimeters or meters instead of at one localized spot within the fiber, minimizing the risk of damage. Thorlabs manufactures and sells 0.22 NA double-clad multimode fiber, which boasts very high, megawatt range power handling.

Photodarkening
A second damage mechanism, called photodarkening or solarization, can occur in fibers used with ultraviolet or short-wavelength visible light, particularly those with germanium-doped cores. Fibers used at these wavelengths will experience increased attenuation over time. The mechanism that causes photodarkening is largely unknown, but several fiber designs have been developed to mitigate it. For example, fibers with a very low hydroxyl ion (OH) content have been found to resist photodarkening and using other dopants, such as fluorine, can also reduce photodarkening.

Even with the above strategies in place, all fibers eventually experience photodarkening when used with UV or short-wavelength light, and thus, fibers used at these wavelengths should be considered consumables.

Preparation and Handling of Optical Fibers

General Cleaning and Operation Guidelines
These general cleaning and operation guidelines are recommended for all fiber optic products. Users should still follow specific guidelines for an individual product as outlined in the support documentation or manual. Damage threshold calculations only apply when all appropriate cleaning and handling procedures are followed.

  1. All light sources should be turned off prior to installing or integrating optical fibers (terminated or bare). This ensures that focused beams of light are not incident on fragile parts of the connector or fiber, which can possibly cause damage.

  2. The power-handling capability of an optical fiber is directly linked to the quality of the fiber/connector end face. Always inspect the fiber end prior to connecting the fiber to an optical system. The fiber end face should be clean and clear of dirt and other contaminants that can cause scattering of coupled light. Bare fiber should be cleaved prior to use and users should inspect the fiber end to ensure a good quality cleave is achieved.

  3. If an optical fiber is to be spliced into the optical system, users should first verify that the splice is of good quality at a low optical power prior to high-power use. Poor splice quality may increase light scattering at the splice interface, which can be a source of fiber damage.

  4. Users should use low power when aligning the system and optimizing coupling; this minimizes exposure of other parts of the fiber (other than the core) to light. Damage from scattered light can occur if a high power beam is focused on the cladding, coating, or connector.

Tips for Using Fiber at Higher Optical Power
Optical fibers and fiber components should generally be operated within safe power level limits, but under ideal conditions (very good optical alignment and very clean optical end faces), the power handling of a fiber component may be increased. Users must verify the performance and stability of a fiber component within their system prior to increasing input or output power and follow all necessary safety and operation instructions. The tips below are useful suggestions when considering increasing optical power in an optical fiber or component.

  1. Splicing a fiber component into a system using a fiber splicer can increase power handling as it minimizes possibility of air/fiber interface damage. Users should follow all appropriate guidelines to prepare and make a high-quality fiber splice. Poor splices can lead to scattering or regions of highly localized heat at the splice interface that can damage the fiber.

  2. After connecting the fiber or component, the system should be tested and aligned using a light source at low power. The system power can be ramped up slowly to the desired output power while periodically verifying all components are properly aligned and that coupling efficiency is not changing with respect to optical launch power.

  3. Bend losses that result from sharply bending a fiber can cause light to leak from the fiber in the stressed area. When operating at high power, the localized heating that can occur when a large amount of light escapes a small localized area (the stressed region) can damage the fiber. Avoid disturbing or accidently bending fibers during operation to minimize bend losses.

  4. Users should always choose the appropriate optical fiber for a given application. For example, large-mode-area fibers are a good alternative to standard single mode fibers in high-power applications as they provide good beam quality with a larger MFD, decreasing the power density on the air/fiber interface.

  5. Step-index silica single mode fibers are normally not used for ultraviolet light or high-peak-power pulsed applications due to the high spatial power densities associated with these applications.


Please Give Us Your Feedback
 
Email Feedback On
(Optional)
Contact Me:
Your email address will NOT be displayed.
 
 
Please type the following key into the field to submit this form:
Click Here if you can not read the security code.
This code is to prevent automated spamming of our site
Thank you for your understanding.
  
 
Would this product be useful to you?   Little Use  1234Very Useful

Enter Comments Below:
 
Characters remaining  8000   
Posted Comments:
Poster:bdada
Posted Date:2011-03-08 18:45:00.0
Response from Buki: Thank you for your feedback Michael. For the 460HP fiber, at 532nm, the cladding refractive index is about 1.461, and the core refractive index is about 1.467. For the S460-HP, at 633nm, the core refractive index is about 1.46873 and the cladding refractive index is about 1.46298.
Poster:michael.ireland
Posted Date:2011-03-07 17:47:54.0
I need to know the cladding refractive index (at ~550nm or some nearby wavelength) for the 460HP and S460-HP fibers. This doesnt seem to be given in the spec sheets.
Poster:bdada
Posted Date:2011-03-07 15:24:00.0
Response from Buki. For single mode fiber, a flat cleave would provide a good optical surface that makes it unnecessary for the end to be polished. We have two products for fiber cleaving: XL411 and S90W.
Poster:cmarkle
Posted Date:2011-03-07 13:37:42.0
I recently bought some optical fiber (460hp) from you guys and was wondering how to polish the ends. My application does not require a connector but it seems the polishing kits do. Can you Help?
Poster:Adam
Posted Date:2010-03-31 19:40:48.0
A response from Adam at Thorlabs to fahd: We have three methods for stripping this type of fiber. The first is using a mechanical stripper, which would not work for your application. The next two might: Method 2: Chemical Dip in solvent for a few minutes. Jackets will absorb the solvent and swell up. Grab fiber between thumb and index finger (with some tissue in between) and rub swollen portion off. Method 3: Hot Sulfuric Acid Hot sulfuric acid (T=150-180°C). Dip a few minutes or until all acrylate is dissolved. Rinse in clean water after excess acid is drained off. Then, rinse in acetone, then isopropyl alcohol and blow dry. I will email directly with more information about method 2.
Poster:fahd_ali2000
Posted Date:2009-11-24 05:37:46.0
Hello, i have bought SMF-28-100. I have a problem of stripping this fiber. I want to strip from middle in 1 meter fiber but could not, it always break. its very rough from inside. dont know what to do. I appreciate if you can help me. thanks bye
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
S405-XP Support Documentation
S405-XPSingle Mode Optical Fiber, 400 - 680 nm, Ø125 µm Cladding
$14.20
Per Meter
Volume Pricing
Today
SM400 Support Documentation
SM400Single Mode Optical Fiber, 405 - 532 nm, Ø125 µm Cladding
$17.40
Per Meter
Volume Pricing
Today
SM450 Support Documentation
SM450Single Mode Optical Fiber, 488 - 633 nm, Ø125 µm Cladding
$7.25
Per Meter
Volume Pricing
Today
460HP Support Documentation
460HPSingle Mode Optical Fiber, 450 - 600 nm, Ø125 µm Cladding
$10.40
Per Meter
Volume Pricing
Today

Single Mode Fiber: 600 to 860 nm

Stock Patch Cables Available with These Fibers
SM600 Fiber
Item # Prefix Connectors Length
P1-630A-FC FC/PC to FC/PC 1, 2, 5, or 10 m
P3-630A-FC FC/PC to FC/PC 1, 2, or 5 m
P5-630A-PCAPC FC/PC to FC/APC 1 m
P2-630-PCSMA FC/PC to SMA 1 m
P1-630AR-2 AR-Coated (600 - 800 nm) FC/PC to Uncoated FC/PC 2 m
P5-630AR-2 AR-Coated (600 - 800 nm) FC/PC to Uncoated FC/APC 2 m
P4-630AR-2 AR-Coated (600 - 800 nm) FC/APC to Uncoated FC/PC 2 m
P3-630AR-2 AR-Coated (600 - 800 nm) FC/APC to Uncoated FC/APC 2 m
P1-630P-FC FC/PC to FC/PC (Low Insertion Loss) 1, 2, or 5 m
P3-630P-FC FC/APC to FC/APC (Low Insertion Loss) 1, 2, or 5 m
P5-630P-PCAPC-1 FC/PC to FC/APC (Low Insertion Loss) 1 m

Custom cables are also available. Click here for details.

Custom Patch Cables
Stock Single Mode Patch Cables

Features

  • Shipped from Stock
  • No Minimums
  • True Single Mode Operation for HeNe and All Visible Laser Diodes
  • Acrylate Coating
  • Exceptional Core/Clad Concentricity
  • 630HP Offers Tight Second Mode Cut-Off Tolerances
Item # Operating Wavelength Mode Field Diameter Cladding Coating Cut-Off Wavelengthc
SM600 633 -780 nma 3.6 - 5.3 µm @ 633 nmb 125 ± 1 µm 245 ± 15 µm 500 - 600 nm
S630-HP 630 - 860 nm 4.2 ± 0.5 µm @ 630 nm 125 ± 1.0 µm 245 ± 15 µm 590 ± 30 nm
630HP 600 - 770 nm 4.0 ± 0.5 µm @ 630 nm 125 ± 1 µm 245 ± 15 µm 570 ± 30 nm
Item # Short-Term Bend Radius Long-Term Bend Radius Max Attenuation NA Core Index Cladding Index
SM600 ≥5 mm ≥25 mm ≤15 dB/kmd 0.10 - 0.14 600 nm: 1.46147e
700 nm: 1.45872e 
800 nm: 1.45675e
600 nm: 1.45804e
700 nm: 1.45530e 
800 nm: 1.45332e
S630-HP ≥6 mm ≥13 mm ≤10 dB/km @ 630 nm 0.12 Callf Callf
630HP - - ≤12 dB/km @ 630 nm 0.13 Callf Callf
  • The wavelength range is the spectral region between the cutoff wavelength and the bend edge, in which the fiber transmits the TEM00 mode with low attenuation. For this fiber, the bend edge wavelength is typically 200 nm longer than the cut-off wavelength. At the operating wavelengths between 633 nm and 780 nm, the launched power must be considered carefully as these fibers have germanosilicate cores and as such are susceptible to color center generation.
  • MFD is a nominal, calculated value, estimated at the operating wavelength(s) using a typical value of NA & cutoff wavelength. Please see the MFD Definition tab for details.
  • The wavelength at which the fiber only allows a single mode to propogate.
  • Attenuation is worst-case value, quoted for the shortest wavelength.
  • The indices provided are for an NA of 0.10.
  • Please contact our Technical Support Staff to learn more about the refractive index of this fiber, as we are not permitted to publish this information on our website.

Definition of the Mode Field Diameter

The mode field diameter (MFD) is one measure of the beam size of light propagating in a single mode fiber. It is a function of wavelength, core radius, and the refractive indices of the core and cladding. While much of the light in an optical fiber is trapped within the fiber core, a small fraction propagates in the cladding. For a Gaussian power distribution, the MFD is the diameter where the optical power is reduced to 1/e2 from its peak level.

Measurement of MFD
The measurement of MFD is accomplished by the Variable Aperture Method in the Far Field (VAMFF). An aperture is placed in the far field of the fiber output, and the intensity is measured. As successively smaller apertures are placed in the beam, the intensity levels are measured for each aperture; the data can then be plotted as power vs. the sine of the aperture half-angle (or the numerical aperture).

The MFD is then determined using Petermann's second definition, which is a mathematical model that does not assume a specific shape of power distribution. The MFD in the near field can be determined from this far-field measurement using the Hankel Transform.

Laser-Induced Damage in Silica Optical Fibers

The following tutorial details damage mechanisms relevant to unterminated (bare) fiber, terminated optical fiber, and other fiber components from laser light sources. These mechanisms include damage that occurs at the air / glass interface (when free-space coupling or when using connectors) and in the optical fiber itself. A fiber component, such as a bare fiber, patch cable, or fused coupler, may have multiple potential avenues for damage (e.g., connectors, fiber end faces, and the device itself). The maximum power that a fiber can handle will always be limited by the lowest limit of any of these damage mechanisms.

While the damage threshold can be estimated using scaling relations and general rules, absolute damage thresholds in optical fibers are very application dependent and user specific. Users can use this guide to estimate a safe power level that minimizes the risk of damage. Following all appropriate preparation and handling guidelines, users should be able to operate a fiber component up to the specified maximum power level; if no maximum is specified for a component, users should abide by the "practical safe level" described below for safe operation of the component. Factors that can reduce power handling and cause damage to a fiber component include, but are not limited to, misalignment during fiber coupling, contamination of the fiber end face, or imperfections in the fiber itself. For further discussion about an optical fiber’s power handling abilities for a specific application, please contact Thorlabs’ Tech Support.

Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Undamaged Fiber End
Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Damaged Fiber End

Damage at the Air / Glass Interface

There are several potential damage mechanisms that can occur at the air / glass interface. Light is incident on this interface when free-space coupling or when two fibers are mated using optical connectors. High-intensity light can damage the end face leading to reduced power handling and permanent damage to the fiber. For fibers terminated with optical connectors where the connectors are fixed to the fiber ends using epoxy, the heat generated by high-intensity light can burn the epoxy and leave residues on the fiber facet directly in the beam path.

Estimated Optical Power Densities on Air / Glass Interfacea
Type Theoretical Damage Thresholdb Practical Safe Levelc
CW
(Average Power)
~1 MW/cm2 ~250 kW/cm2
10 ns Pulsed
(Peak Power)
~5 GW/cm2 ~1 GW/cm2
  • All values are specified for unterminated (bare) silica fiber and apply for free space coupling into a clean fiber end face.
  • This is an estimated maximum power density that can be incident on a fiber end face without risking damage. Verification of the performance and reliability of fiber components in the system before operating at high power must be done by the user, as it is highly system dependent.
  • This is the estimated safe optical power density that can be incident on a fiber end face without damaging the fiber under most operating conditions.

Damage Mechanisms on the Bare Fiber End Face

Damage mechanisms on a fiber end face can be modeled similarly to bulk optics, and industry-standard damage thresholds for UV Fused Silica substrates can be applied to silica-based fiber. However, unlike bulk optics, the relevant surface areas and beam diameters involved at the air / glass interface of an optical fiber are very small, particularly for coupling into single mode (SM) fiber. therefore, for a given power density, the power incident on the fiber needs to be lower for a smaller beam diameter.

The table to the right lists two thresholds for optical power densities: a theoretical damage threshold and a "practical safe level". In general, the theoretical damage threshold represents the estimated maximum power density that can be incident on the fiber end face without risking damage with very good fiber end face and coupling conditions. The "practical safe level" power density represents minimal risk of fiber damage. Operating a fiber or component beyond the practical safe level is possible, but users must follow the appropriate handling instructions and verify performance at low powers prior to use.

Calculating the Effective Area for Single Mode and Multimode Fibers
The effective area for single mode (SM) fiber is defined by the mode field diameter (MFD), which is the cross-sectional area through which light propagates in the fiber; this area includes the fiber core and also a portion of the cladding. To achieve good efficiency when coupling into a single mode fiber, the diameter of the input beam must match the MFD of the fiber.

As an example, SM400 single mode fiber has a mode field diameter (MFD) of ~Ø3 µm operating at 400 nm, while the MFD for SMF-28 Ultra single mode fiber operating at 1550 nm is Ø10.5 µm. The effective area for these fibers can be calculated as follows:

SM400 Fiber: Area = Pi x (MFD/2)2 = Pi x (1.5 µm)2 = 7.07 µm= 7.07 x 10-8 cm2

 SMF-28 Ultra Fiber: Area = Pi x (MFD/2)2 = Pi x (5.25 µm)2 = 86.6 µm= 8.66 x 10-7 cm2

To estimate the power level that a fiber facet can handle, the power density is multiplied by the effective area. Please note that this calculation assumes a uniform intensity profile, but most laser beams exhibit a Gaussian-like shape within single mode fiber, resulting in a higher power density at the center of the beam compared to the edges. Therefore, these calculations will slightly overestimate the power corresponding to the damage threshold or the practical safe level. Using the estimated power densities assuming a CW light source, we can determine the corresponding power levels as:

SM400 Fiber: 7.07 x 10-8 cm2 x 1 MW/cm2 = 7.1 x 10-8 MW = 71 mW (Theoretical Damage Threshold)
     7.07 x 10-8 cm2 x 250 kW/cm2 = 1.8 x 10-5 kW = 18 mW (Practical Safe Level)

SMF-28 Ultra Fiber: 8.66 x 10-7 cm2 x 1 MW/cm2 = 8.7 x 10-7 MW = 870 mW (Theoretical Damage Threshold)
           8.66 x 10-7 cm2 x 250 kW/cm2 = 2.1 x 10-4 kW = 210 mW (Practical Safe Level)

The effective area of a multimode (MM) fiber is defined by the core diameter, which is typically far larger than the MFD of an SM fiber. For optimal coupling, Thorlabs recommends focusing a beam to a spot roughly 70 - 80% of the core diameter. The larger effective area of MM fibers lowers the power density on the fiber end face, allowing higher optical powers (typically on the order of kilowatts) to be coupled into multimode fiber without damage.

Damage Mechanisms Related to Ferrule / Connector Termination


Click to Enlarge
Plot showing approximate power handling levels for single mode silica optical fiber with a termination. Each line shows the estimated power level due to a specific damage mechanism. The maximum power handling is limited by the lowest power level from all relevant damage mechanisms (indicated by a solid line).

Fibers terminated with optical connectors have additional power handling considerations. Fiber is typically terminated using epoxy to bond the fiber to a ceramic or steel ferrule. When light is coupled into the fiber through a connector, light that does not enter the core and propagate down the fiber is scattered into the outer layers of the fiber, into the ferrule, and the epoxy used to hold the fiber in the ferrule. If the light is intense enough, it can burn the epoxy, causing it to vaporize and deposit a residue on the face of the connector. This results in localized absorption sites on the fiber end face that reduce coupling efficiency and increase scattering, causing further damage.

For several reasons, epoxy-related damage is dependent on the wavelength. In general, light scatters more strongly at short wavelengths than at longer wavelengths. Misalignment when coupling is also more likely due to the small MFD of short-wavelength SM fiber that also produces more scattered light.

To minimize the risk of burning the epoxy, fiber connectors can be constructed to have an epoxy-free air gap between the optical fiber and ferrule near the fiber end face. Our high-power multimode fiber patch cables use connectors with this design feature.

Determining Power Handling with Multiple Damage Mechanisms

When fiber cables or components have multiple avenues for damage (e.g., fiber patch cables), the maximum power handling is always limited by the lowest damage threshold that is relevant to the fiber component.

As an illustrative example, the graph to the right shows an estimate of the power handling limitations of a single mode fiber patch cable due to damage to the fiber end face and damage via an optical connector. The total power handling of a terminated fiber at a given wavelength is limited by the lower of the two limitations at any given wavelength (indicated by the solid lines). A single mode fiber operating at around 488 nm is primarily limited by damage to the fiber end face (blue solid line), but fibers operating at 1550 nm are limited by damage to the optical connector (red solid line).

In the case of a multimode fiber, the effective mode area is defined by the core diameter, which is larger than the effective mode area for SM fiber. This results in a lower power density on the fiber end face and allows higher optical powers (on the order of kilowatts) to be coupled into the fiber without damage (not shown in graph). However, the damage limit of the ferrule / connector termination remains unchanged and as a result, the maximum power handling for a multimode fiber is limited by the ferrule and connector termination. 

Please note that these are rough estimates of power levels where damage is very unlikely with proper handling and alignment procedures. It is worth noting that optical fibers are frequently used at power levels above those described here. However, these applications typically require expert users and testing at lower powers first to minimize risk of damage. Even still, optical fiber components should be considered a consumable lab supply if used at high power levels.

Intrinsic Damage Threshold

In addition to damage mechanisms at the air / glass interface, optical fibers also display power handling limitations due to damage mechanisms within the optical fiber itself. These limitations will affect all fiber components as they are intrinsic to the fiber itself. Two categories of damage within the fiber are damage from bend losses and damage from photodarkening. 

Bend Losses
Bend losses occur when a fiber is bent to a point where light traveling in the core is incident on the core/cladding interface at an angle higher than the critical angle, making total internal reflection impossible. Under these circumstances, light escapes the fiber, often in a localized area. The light escaping the fiber typically has a high power density, which burns the fiber coating as well as any surrounding furcation tubing.

A special category of optical fiber, called double-clad fiber, can reduce the risk of bend-loss damage by allowing the fiber’s cladding (2nd layer) to also function as a waveguide in addition to the core. By making the critical angle of the cladding/coating interface higher than the critical angle of the core/clad interface, light that escapes the core is loosely confined within the cladding. It will then leak out over a distance of centimeters or meters instead of at one localized spot within the fiber, minimizing the risk of damage. Thorlabs manufactures and sells 0.22 NA double-clad multimode fiber, which boasts very high, megawatt range power handling.

Photodarkening
A second damage mechanism, called photodarkening or solarization, can occur in fibers used with ultraviolet or short-wavelength visible light, particularly those with germanium-doped cores. Fibers used at these wavelengths will experience increased attenuation over time. The mechanism that causes photodarkening is largely unknown, but several fiber designs have been developed to mitigate it. For example, fibers with a very low hydroxyl ion (OH) content have been found to resist photodarkening and using other dopants, such as fluorine, can also reduce photodarkening.

Even with the above strategies in place, all fibers eventually experience photodarkening when used with UV or short-wavelength light, and thus, fibers used at these wavelengths should be considered consumables.

Preparation and Handling of Optical Fibers

General Cleaning and Operation Guidelines
These general cleaning and operation guidelines are recommended for all fiber optic products. Users should still follow specific guidelines for an individual product as outlined in the support documentation or manual. Damage threshold calculations only apply when all appropriate cleaning and handling procedures are followed.

  1. All light sources should be turned off prior to installing or integrating optical fibers (terminated or bare). This ensures that focused beams of light are not incident on fragile parts of the connector or fiber, which can possibly cause damage.

  2. The power-handling capability of an optical fiber is directly linked to the quality of the fiber/connector end face. Always inspect the fiber end prior to connecting the fiber to an optical system. The fiber end face should be clean and clear of dirt and other contaminants that can cause scattering of coupled light. Bare fiber should be cleaved prior to use and users should inspect the fiber end to ensure a good quality cleave is achieved.

  3. If an optical fiber is to be spliced into the optical system, users should first verify that the splice is of good quality at a low optical power prior to high-power use. Poor splice quality may increase light scattering at the splice interface, which can be a source of fiber damage.

  4. Users should use low power when aligning the system and optimizing coupling; this minimizes exposure of other parts of the fiber (other than the core) to light. Damage from scattered light can occur if a high power beam is focused on the cladding, coating, or connector.

Tips for Using Fiber at Higher Optical Power
Optical fibers and fiber components should generally be operated within safe power level limits, but under ideal conditions (very good optical alignment and very clean optical end faces), the power handling of a fiber component may be increased. Users must verify the performance and stability of a fiber component within their system prior to increasing input or output power and follow all necessary safety and operation instructions. The tips below are useful suggestions when considering increasing optical power in an optical fiber or component.

  1. Splicing a fiber component into a system using a fiber splicer can increase power handling as it minimizes possibility of air/fiber interface damage. Users should follow all appropriate guidelines to prepare and make a high-quality fiber splice. Poor splices can lead to scattering or regions of highly localized heat at the splice interface that can damage the fiber.

  2. After connecting the fiber or component, the system should be tested and aligned using a light source at low power. The system power can be ramped up slowly to the desired output power while periodically verifying all components are properly aligned and that coupling efficiency is not changing with respect to optical launch power.

  3. Bend losses that result from sharply bending a fiber can cause light to leak from the fiber in the stressed area. When operating at high power, the localized heating that can occur when a large amount of light escapes a small localized area (the stressed region) can damage the fiber. Avoid disturbing or accidently bending fibers during operation to minimize bend losses.

  4. Users should always choose the appropriate optical fiber for a given application. For example, large-mode-area fibers are a good alternative to standard single mode fibers in high-power applications as they provide good beam quality with a larger MFD, decreasing the power density on the air/fiber interface.

  5. Step-index silica single mode fibers are normally not used for ultraviolet light or high-peak-power pulsed applications due to the high spatial power densities associated with these applications.


Please Give Us Your Feedback
 
Email Feedback On
(Optional)
Contact Me:
Your email address will NOT be displayed.
 
 
Please type the following key into the field to submit this form:
Click Here if you can not read the security code.
This code is to prevent automated spamming of our site
Thank you for your understanding.
  
 
Would this product be useful to you?   Little Use  1234Very Useful

Enter Comments Below:
 
Characters remaining  8000   
Posted Comments:
Poster:Thorlabs
Posted Date:2010-12-07 15:53:01.0
Response from Javier at Thorlabs to Peter: We will gladly send you a quotation. we will contact you shortly to get your contact details.
Poster:taenzer
Posted Date:2010-12-07 14:54:24.0
please send me offer for 2000 m of single mode fibre SM600 thanks Peter Taenzer, Germany
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
SM600 Support Documentation
SM600Single Mode Optical Fiber, 633 - 780 nm, Ø125 µm Cladding
$4.85
Per Meter
Volume Pricing
Today
S630-HP Support Documentation
S630-HPSingle Mode Optical Fiber, 630 - 860 nm, Ø125 µm Cladding
$9.10
Per Meter
Volume Pricing
Today
630HP Support Documentation
630HPSingle Mode Optical Fiber, 600 - 770 nm, Ø125 µm Cladding
$5.55
Per Meter
Volume Pricing
Today

Single Mode Fiber: 780 to 970 nm

Stock Patch Cables Available with These Fibers
780HP Fiber
SM800-5.6-125 Fiber
Item # Prefix Connectors Length
P1-830A-FC FC/PC to FC/PC 1, 2, 5, or 10 m
P3-830A-FC FC/APC to FC/APC 1, 2, or 5 m
P5-830A-PCAPC FC/PC to FC/APC 1 m
P2-830A-PCSMA FC/PC to SMA 1 m

Custom cables are also available. Click here for details.

Custom Patch Cables
Stock Single Mode Patch Cables

Features

  • Shipped from Stock
  • No Minimums
  • Acrylate Jacket
  • Exceptional Uniformity
  • Exceptional Core/Clad Concentricity
  • 780HP Offers Tight Second Mode Cut-Off Tolerances
  • SM800G80 Offers Enhanced Bend Insensitivity
Item # Operating Wavelength Mode Field Diameter Cladding Coating Cut-Off Wavelength
780HP 780 - 970 nm 5.0 ± 0.5 µm @ 850 nm 125 ± 1 µm 245 ± 15 µm 730 ± 30 nm
SM800-5.6-125 830 - 980 nma 4.7 - 6.9 µmb @ 830 nm 125 ± 1.0 µm 245 ± 15 µm 660 - 800 nm
SM800G80 830 - 980 nma 3.75 - 4.9 µm @ 830 nm 80 ± 1 µm 170 ± 10 µm 660 - 800 nm
Item # Short-Term Bend Radius Long-Term Bend Radius Attenuation (Max) NA Core Index Cladding Index
780HP - - ≤4.0 dB/km @ 780 nm
≤3.5 dB/km @ 850 nm
0.13 Calld Calld
SM800-5.6-125 ≥5 mm ≥25 mm <5 dB/kmc 0.10 - 0.14 830 nm: 1.45625e 830 nm: 1.45282e
SM800G80 ≥5 mm ≥12 mm
(or 38 mm for 25 Year Life)
≤3.0 dB/kmc 0.14 - 0.18 830 nm: 1.45954f 830 nm: 1.45282f
  • The wavelength range is the spectral region between the cutoff wavelength and the bend edge, in which the fiber transmits the TEM00 mode with low attenuation. For this fiber, the bend edge wavelength is typically 200 nm longer than the cut-off wavelength. At the design wavelength of 830 nm, the launched power must be considered carefully as these fibers have germanosilicate cores and as such are susceptible to color center generation.
  • MFD is a nominal, calculated value, estimated at the operating wavelength(s) using a typical value of NA & cutoff wavelength. Please see the MFD Definition tab for details.
  • Attenuation is a worse-case value, quoted for the shortest design wavelength.
  • Please contact our Technical Support Staff to learn more about the refractive index of this fiber, as we are not permitted to publish this information on our website.
  • The index provided is for an NA of 0.10.
  • The index provided is for an NA of 0.14.

Definition of the Mode Field Diameter

The mode field diameter (MFD) is one measure of the beam size of light propagating in a single mode fiber. It is a function of wavelength, core radius, and the refractive indices of the core and cladding. While much of the light in an optical fiber is trapped within the fiber core, a small fraction propagates in the cladding. For a Gaussian power distribution, the MFD is the diameter where the optical power is reduced to 1/e2 from its peak level.

Measurement of MFD
The measurement of MFD is accomplished by the Variable Aperture Method in the Far Field (VAMFF). An aperture is placed in the far field of the fiber output, and the intensity is measured. As successively smaller apertures are placed in the beam, the intensity levels are measured for each aperture; the data can then be plotted as power vs. the sine of the aperture half-angle (or the numerical aperture).

The MFD is then determined using Petermann's second definition, which is a mathematical model that does not assume a specific shape of power distribution. The MFD in the near field can be determined from this far-field measurement using the Hankel Transform.

Laser-Induced Damage in Silica Optical Fibers

The following tutorial details damage mechanisms relevant to unterminated (bare) fiber, terminated optical fiber, and other fiber components from laser light sources. These mechanisms include damage that occurs at the air / glass interface (when free-space coupling or when using connectors) and in the optical fiber itself. A fiber component, such as a bare fiber, patch cable, or fused coupler, may have multiple potential avenues for damage (e.g., connectors, fiber end faces, and the device itself). The maximum power that a fiber can handle will always be limited by the lowest limit of any of these damage mechanisms.

While the damage threshold can be estimated using scaling relations and general rules, absolute damage thresholds in optical fibers are very application dependent and user specific. Users can use this guide to estimate a safe power level that minimizes the risk of damage. Following all appropriate preparation and handling guidelines, users should be able to operate a fiber component up to the specified maximum power level; if no maximum is specified for a component, users should abide by the "practical safe level" described below for safe operation of the component. Factors that can reduce power handling and cause damage to a fiber component include, but are not limited to, misalignment during fiber coupling, contamination of the fiber end face, or imperfections in the fiber itself. For further discussion about an optical fiber’s power handling abilities for a specific application, please contact Thorlabs’ Tech Support.

Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Undamaged Fiber End
Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Damaged Fiber End

Damage at the Air / Glass Interface

There are several potential damage mechanisms that can occur at the air / glass interface. Light is incident on this interface when free-space coupling or when two fibers are mated using optical connectors. High-intensity light can damage the end face leading to reduced power handling and permanent damage to the fiber. For fibers terminated with optical connectors where the connectors are fixed to the fiber ends using epoxy, the heat generated by high-intensity light can burn the epoxy and leave residues on the fiber facet directly in the beam path.

Estimated Optical Power Densities on Air / Glass Interfacea
Type Theoretical Damage Thresholdb Practical Safe Levelc
CW
(Average Power)
~1 MW/cm2 ~250 kW/cm2
10 ns Pulsed
(Peak Power)
~5 GW/cm2 ~1 GW/cm2
  • All values are specified for unterminated (bare) silica fiber and apply for free space coupling into a clean fiber end face.
  • This is an estimated maximum power density that can be incident on a fiber end face without risking damage. Verification of the performance and reliability of fiber components in the system before operating at high power must be done by the user, as it is highly system dependent.
  • This is the estimated safe optical power density that can be incident on a fiber end face without damaging the fiber under most operating conditions.

Damage Mechanisms on the Bare Fiber End Face

Damage mechanisms on a fiber end face can be modeled similarly to bulk optics, and industry-standard damage thresholds for UV Fused Silica substrates can be applied to silica-based fiber. However, unlike bulk optics, the relevant surface areas and beam diameters involved at the air / glass interface of an optical fiber are very small, particularly for coupling into single mode (SM) fiber. therefore, for a given power density, the power incident on the fiber needs to be lower for a smaller beam diameter.

The table to the right lists two thresholds for optical power densities: a theoretical damage threshold and a "practical safe level". In general, the theoretical damage threshold represents the estimated maximum power density that can be incident on the fiber end face without risking damage with very good fiber end face and coupling conditions. The "practical safe level" power density represents minimal risk of fiber damage. Operating a fiber or component beyond the practical safe level is possible, but users must follow the appropriate handling instructions and verify performance at low powers prior to use.

Calculating the Effective Area for Single Mode and Multimode Fibers
The effective area for single mode (SM) fiber is defined by the mode field diameter (MFD), which is the cross-sectional area through which light propagates in the fiber; this area includes the fiber core and also a portion of the cladding. To achieve good efficiency when coupling into a single mode fiber, the diameter of the input beam must match the MFD of the fiber.

As an example, SM400 single mode fiber has a mode field diameter (MFD) of ~Ø3 µm operating at 400 nm, while the MFD for SMF-28 Ultra single mode fiber operating at 1550 nm is Ø10.5 µm. The effective area for these fibers can be calculated as follows:

SM400 Fiber: Area = Pi x (MFD/2)2 = Pi x (1.5 µm)2 = 7.07 µm= 7.07 x 10-8 cm2

 SMF-28 Ultra Fiber: Area = Pi x (MFD/2)2 = Pi x (5.25 µm)2 = 86.6 µm= 8.66 x 10-7 cm2

To estimate the power level that a fiber facet can handle, the power density is multiplied by the effective area. Please note that this calculation assumes a uniform intensity profile, but most laser beams exhibit a Gaussian-like shape within single mode fiber, resulting in a higher power density at the center of the beam compared to the edges. Therefore, these calculations will slightly overestimate the power corresponding to the damage threshold or the practical safe level. Using the estimated power densities assuming a CW light source, we can determine the corresponding power levels as:

SM400 Fiber: 7.07 x 10-8 cm2 x 1 MW/cm2 = 7.1 x 10-8 MW = 71 mW (Theoretical Damage Threshold)
     7.07 x 10-8 cm2 x 250 kW/cm2 = 1.8 x 10-5 kW = 18 mW (Practical Safe Level)

SMF-28 Ultra Fiber: 8.66 x 10-7 cm2 x 1 MW/cm2 = 8.7 x 10-7 MW = 870 mW (Theoretical Damage Threshold)
           8.66 x 10-7 cm2 x 250 kW/cm2 = 2.1 x 10-4 kW = 210 mW (Practical Safe Level)

The effective area of a multimode (MM) fiber is defined by the core diameter, which is typically far larger than the MFD of an SM fiber. For optimal coupling, Thorlabs recommends focusing a beam to a spot roughly 70 - 80% of the core diameter. The larger effective area of MM fibers lowers the power density on the fiber end face, allowing higher optical powers (typically on the order of kilowatts) to be coupled into multimode fiber without damage.

Damage Mechanisms Related to Ferrule / Connector Termination


Click to Enlarge
Plot showing approximate power handling levels for single mode silica optical fiber with a termination. Each line shows the estimated power level due to a specific damage mechanism. The maximum power handling is limited by the lowest power level from all relevant damage mechanisms (indicated by a solid line).

Fibers terminated with optical connectors have additional power handling considerations. Fiber is typically terminated using epoxy to bond the fiber to a ceramic or steel ferrule. When light is coupled into the fiber through a connector, light that does not enter the core and propagate down the fiber is scattered into the outer layers of the fiber, into the ferrule, and the epoxy used to hold the fiber in the ferrule. If the light is intense enough, it can burn the epoxy, causing it to vaporize and deposit a residue on the face of the connector. This results in localized absorption sites on the fiber end face that reduce coupling efficiency and increase scattering, causing further damage.

For several reasons, epoxy-related damage is dependent on the wavelength. In general, light scatters more strongly at short wavelengths than at longer wavelengths. Misalignment when coupling is also more likely due to the small MFD of short-wavelength SM fiber that also produces more scattered light.

To minimize the risk of burning the epoxy, fiber connectors can be constructed to have an epoxy-free air gap between the optical fiber and ferrule near the fiber end face. Our high-power multimode fiber patch cables use connectors with this design feature.

Determining Power Handling with Multiple Damage Mechanisms

When fiber cables or components have multiple avenues for damage (e.g., fiber patch cables), the maximum power handling is always limited by the lowest damage threshold that is relevant to the fiber component.

As an illustrative example, the graph to the right shows an estimate of the power handling limitations of a single mode fiber patch cable due to damage to the fiber end face and damage via an optical connector. The total power handling of a terminated fiber at a given wavelength is limited by the lower of the two limitations at any given wavelength (indicated by the solid lines). A single mode fiber operating at around 488 nm is primarily limited by damage to the fiber end face (blue solid line), but fibers operating at 1550 nm are limited by damage to the optical connector (red solid line).

In the case of a multimode fiber, the effective mode area is defined by the core diameter, which is larger than the effective mode area for SM fiber. This results in a lower power density on the fiber end face and allows higher optical powers (on the order of kilowatts) to be coupled into the fiber without damage (not shown in graph). However, the damage limit of the ferrule / connector termination remains unchanged and as a result, the maximum power handling for a multimode fiber is limited by the ferrule and connector termination. 

Please note that these are rough estimates of power levels where damage is very unlikely with proper handling and alignment procedures. It is worth noting that optical fibers are frequently used at power levels above those described here. However, these applications typically require expert users and testing at lower powers first to minimize risk of damage. Even still, optical fiber components should be considered a consumable lab supply if used at high power levels.

Intrinsic Damage Threshold

In addition to damage mechanisms at the air / glass interface, optical fibers also display power handling limitations due to damage mechanisms within the optical fiber itself. These limitations will affect all fiber components as they are intrinsic to the fiber itself. Two categories of damage within the fiber are damage from bend losses and damage from photodarkening. 

Bend Losses
Bend losses occur when a fiber is bent to a point where light traveling in the core is incident on the core/cladding interface at an angle higher than the critical angle, making total internal reflection impossible. Under these circumstances, light escapes the fiber, often in a localized area. The light escaping the fiber typically has a high power density, which burns the fiber coating as well as any surrounding furcation tubing.

A special category of optical fiber, called double-clad fiber, can reduce the risk of bend-loss damage by allowing the fiber’s cladding (2nd layer) to also function as a waveguide in addition to the core. By making the critical angle of the cladding/coating interface higher than the critical angle of the core/clad interface, light that escapes the core is loosely confined within the cladding. It will then leak out over a distance of centimeters or meters instead of at one localized spot within the fiber, minimizing the risk of damage. Thorlabs manufactures and sells 0.22 NA double-clad multimode fiber, which boasts very high, megawatt range power handling.

Photodarkening
A second damage mechanism, called photodarkening or solarization, can occur in fibers used with ultraviolet or short-wavelength visible light, particularly those with germanium-doped cores. Fibers used at these wavelengths will experience increased attenuation over time. The mechanism that causes photodarkening is largely unknown, but several fiber designs have been developed to mitigate it. For example, fibers with a very low hydroxyl ion (OH) content have been found to resist photodarkening and using other dopants, such as fluorine, can also reduce photodarkening.

Even with the above strategies in place, all fibers eventually experience photodarkening when used with UV or short-wavelength light, and thus, fibers used at these wavelengths should be considered consumables.

Preparation and Handling of Optical Fibers

General Cleaning and Operation Guidelines
These general cleaning and operation guidelines are recommended for all fiber optic products. Users should still follow specific guidelines for an individual product as outlined in the support documentation or manual. Damage threshold calculations only apply when all appropriate cleaning and handling procedures are followed.

  1. All light sources should be turned off prior to installing or integrating optical fibers (terminated or bare). This ensures that focused beams of light are not incident on fragile parts of the connector or fiber, which can possibly cause damage.

  2. The power-handling capability of an optical fiber is directly linked to the quality of the fiber/connector end face. Always inspect the fiber end prior to connecting the fiber to an optical system. The fiber end face should be clean and clear of dirt and other contaminants that can cause scattering of coupled light. Bare fiber should be cleaved prior to use and users should inspect the fiber end to ensure a good quality cleave is achieved.

  3. If an optical fiber is to be spliced into the optical system, users should first verify that the splice is of good quality at a low optical power prior to high-power use. Poor splice quality may increase light scattering at the splice interface, which can be a source of fiber damage.

  4. Users should use low power when aligning the system and optimizing coupling; this minimizes exposure of other parts of the fiber (other than the core) to light. Damage from scattered light can occur if a high power beam is focused on the cladding, coating, or connector.

Tips for Using Fiber at Higher Optical Power
Optical fibers and fiber components should generally be operated within safe power level limits, but under ideal conditions (very good optical alignment and very clean optical end faces), the power handling of a fiber component may be increased. Users must verify the performance and stability of a fiber component within their system prior to increasing input or output power and follow all necessary safety and operation instructions. The tips below are useful suggestions when considering increasing optical power in an optical fiber or component.

  1. Splicing a fiber component into a system using a fiber splicer can increase power handling as it minimizes possibility of air/fiber interface damage. Users should follow all appropriate guidelines to prepare and make a high-quality fiber splice. Poor splices can lead to scattering or regions of highly localized heat at the splice interface that can damage the fiber.

  2. After connecting the fiber or component, the system should be tested and aligned using a light source at low power. The system power can be ramped up slowly to the desired output power while periodically verifying all components are properly aligned and that coupling efficiency is not changing with respect to optical launch power.

  3. Bend losses that result from sharply bending a fiber can cause light to leak from the fiber in the stressed area. When operating at high power, the localized heating that can occur when a large amount of light escapes a small localized area (the stressed region) can damage the fiber. Avoid disturbing or accidently bending fibers during operation to minimize bend losses.

  4. Users should always choose the appropriate optical fiber for a given application. For example, large-mode-area fibers are a good alternative to standard single mode fibers in high-power applications as they provide good beam quality with a larger MFD, decreasing the power density on the air/fiber interface.

  5. Step-index silica single mode fibers are normally not used for ultraviolet light or high-peak-power pulsed applications due to the high spatial power densities associated with these applications.


Please Give Us Your Feedback
 
Email Feedback On
(Optional)
Contact Me:
Your email address will NOT be displayed.
 
 
Please type the following key into the field to submit this form:
Click Here if you can not read the security code.
This code is to prevent automated spamming of our site
Thank you for your understanding.
  
 
Would this product be useful to you?   Little Use  1234Very Useful

Enter Comments Below:
 
Characters remaining  8000   
Posted Comments:
No Comments Posted
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
780HP Support Documentation
780HPSingle Mode Optical Fiber, 780 - 970 nm, Ø125 µm Cladding
$5.55
Per Meter
Volume Pricing
Today
SM800-5.6-125 Support Documentation
SM800-5.6-125Single Mode Optical Fiber, 830 nm, Ø125 µm Cladding
$5.65
Per Meter
Volume Pricing
Today
SM800G80 Support Documentation
SM800G80Customer Inspired!Single Mode Optical Fiber, 830 nm, 0.14-0.18 NA, Ø80 µm Cladding
$4.70
Per Meter
Volume Pricing
Today

Single Mode Fiber: 980 to 1600 nm

Stock Patch Cables Available with These Fibers
SM980-5.8-125 Fiber

Custom cables are also available. Click here for details.

Custom Patch Cables
Stock Single Mode Patch Cables

Features

  • Shipped from Stock
  • No Minimums
  • HI106-100 and HI1060-J9 have 900 µm Hytrel Outer Jacket
  • SM980-5.8-125 has a MFD Matched to Other Fibers used in EDFA Pump Laser Pigtails
  • 980HP and 1060XP Offer a Tight Second Mode Cut-Off Tolerance
  • SM980G80 Offers Enhanced Bend Insensitivity
Item # Operating Wavelength Mode Field Diameter Cladding Coating Cut-Off Wavelength
SM980-5.8-125 980 - 1550 nm 5.3 - 6.4 µm @ 980 nma 125 ± 1 µm 245 ± 15 µm 870 - 970 nm
SM980G80 980 - 1550 nm 4.2 - 4.9 µm @ 980 nm 80 ± 1 µm 170 ± 10 µm 870 - 970 nm
HI1060-J9 980 - 1060 nm 5.9 ± 0.3 µm @ 980 nm
6.2 ± 0.3 µm @ 1060 nm
125 ± 0.5 µm 245 ± 10 µm 920 ± 50 nm
1060XP 980 - 1600 nm 5.9 ± 0.5 µm @ 980 nm
6.2 ± 0.5 µm @ 1060 nm
9.5 ± 0.5 µm @ 1550 nm
125 ± 0.5 µm 245 ± 10 µm 920 ± 30 nm
980HP 980 - 1600 nm 4.2 ± 0.5 µm @ 980 nm
6.8 ± 0.5 µm @ 1550 nm
125 ± 1 µm 245 ± 15 µm 920 ± 30 nm
Item # Short-Term Bend Radius Long-Term Bend Radius Attenuation (Max) NA Core Index Cladding Index
SM980-5.8-125 ≥5 mm ≥25 mm ≤2.0 dB/kmb 0.13 - 0.15 970 nm: 1.45660c
1310 nm: 1.45259c
1650 nm: 1.44854c
970 nm: 1.45081c
1310 nm: 1.44680c
1650 nm: 1.44275c
SM980G80 ≥5 mm ≥12 mm (or 38 mm for 25 Year Life) ≤2 dB/km 0.17 - 0.19 980 nm: 1.46058d
1310 nm: 1.45670d
1650 nm: 1.45265d
980 nm: 1.45068d
1310 nm: 1.44680d
1650 nm: 1.44275d
HI1060-J9 - - 2.1 dB/km @ 980 nm
1.5 dB/km @1060 nm
0.14 Proprietarye Proprietarye
1060XP - - ≤2.1 dB/km @ 980 nm
≤1.5 dB/km @ 1060 nm
0.14 Callf Callf
980HP ≥6 mm ≥13 mm ≤3.5 dB/km @ 980 nm 0.20 Callg Callg
  • MFD is a nominal, calculated value, estimated at the operating wavelength(s) using a typical value of NA & cut-off wavelength. Please see the MFD Definition tab for details.
  • Attenuation is a worst-case value, quoted for the shortest design wavelength.
  • The indices provided are for an NA of 0.13.
  • The indices provided are for an NA of 0.14.
  • We regret that we cannot provide this proprietary information.
  • Please contact our Technical Support Staff to learn more about the refractive index of this fiber, as we are not permitted to publish this information on our website.

Definition of the Mode Field Diameter

The mode field diameter (MFD) is one measure of the beam size of light propagating in a single mode fiber. It is a function of wavelength, core radius, and the refractive indices of the core and cladding. While much of the light in an optical fiber is trapped within the fiber core, a small fraction propagates in the cladding. For a Gaussian power distribution, the MFD is the diameter where the optical power is reduced to 1/e2 from its peak level.

Measurement of MFD
The measurement of MFD is accomplished by the Variable Aperture Method in the Far Field (VAMFF). An aperture is placed in the far field of the fiber output, and the intensity is measured. As successively smaller apertures are placed in the beam, the intensity levels are measured for each aperture; the data can then be plotted as power vs. the sine of the aperture half-angle (or the numerical aperture).

The MFD is then determined using Petermann's second definition, which is a mathematical model that does not assume a specific shape of power distribution. The MFD in the near field can be determined from this far-field measurement using the Hankel Transform.

Laser-Induced Damage in Silica Optical Fibers

The following tutorial details damage mechanisms relevant to unterminated (bare) fiber, terminated optical fiber, and other fiber components from laser light sources. These mechanisms include damage that occurs at the air / glass interface (when free-space coupling or when using connectors) and in the optical fiber itself. A fiber component, such as a bare fiber, patch cable, or fused coupler, may have multiple potential avenues for damage (e.g., connectors, fiber end faces, and the device itself). The maximum power that a fiber can handle will always be limited by the lowest limit of any of these damage mechanisms.

While the damage threshold can be estimated using scaling relations and general rules, absolute damage thresholds in optical fibers are very application dependent and user specific. Users can use this guide to estimate a safe power level that minimizes the risk of damage. Following all appropriate preparation and handling guidelines, users should be able to operate a fiber component up to the specified maximum power level; if no maximum is specified for a component, users should abide by the "practical safe level" described below for safe operation of the component. Factors that can reduce power handling and cause damage to a fiber component include, but are not limited to, misalignment during fiber coupling, contamination of the fiber end face, or imperfections in the fiber itself. For further discussion about an optical fiber’s power handling abilities for a specific application, please contact Thorlabs’ Tech Support.

Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Undamaged Fiber End
Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Damaged Fiber End

Damage at the Air / Glass Interface

There are several potential damage mechanisms that can occur at the air / glass interface. Light is incident on this interface when free-space coupling or when two fibers are mated using optical connectors. High-intensity light can damage the end face leading to reduced power handling and permanent damage to the fiber. For fibers terminated with optical connectors where the connectors are fixed to the fiber ends using epoxy, the heat generated by high-intensity light can burn the epoxy and leave residues on the fiber facet directly in the beam path.

Estimated Optical Power Densities on Air / Glass Interfacea
Type Theoretical Damage Thresholdb Practical Safe Levelc
CW
(Average Power)
~1 MW/cm2 ~250 kW/cm2
10 ns Pulsed
(Peak Power)
~5 GW/cm2 ~1 GW/cm2
  • All values are specified for unterminated (bare) silica fiber and apply for free space coupling into a clean fiber end face.
  • This is an estimated maximum power density that can be incident on a fiber end face without risking damage. Verification of the performance and reliability of fiber components in the system before operating at high power must be done by the user, as it is highly system dependent.
  • This is the estimated safe optical power density that can be incident on a fiber end face without damaging the fiber under most operating conditions.

Damage Mechanisms on the Bare Fiber End Face

Damage mechanisms on a fiber end face can be modeled similarly to bulk optics, and industry-standard damage thresholds for UV Fused Silica substrates can be applied to silica-based fiber. However, unlike bulk optics, the relevant surface areas and beam diameters involved at the air / glass interface of an optical fiber are very small, particularly for coupling into single mode (SM) fiber. therefore, for a given power density, the power incident on the fiber needs to be lower for a smaller beam diameter.

The table to the right lists two thresholds for optical power densities: a theoretical damage threshold and a "practical safe level". In general, the theoretical damage threshold represents the estimated maximum power density that can be incident on the fiber end face without risking damage with very good fiber end face and coupling conditions. The "practical safe level" power density represents minimal risk of fiber damage. Operating a fiber or component beyond the practical safe level is possible, but users must follow the appropriate handling instructions and verify performance at low powers prior to use.

Calculating the Effective Area for Single Mode and Multimode Fibers
The effective area for single mode (SM) fiber is defined by the mode field diameter (MFD), which is the cross-sectional area through which light propagates in the fiber; this area includes the fiber core and also a portion of the cladding. To achieve good efficiency when coupling into a single mode fiber, the diameter of the input beam must match the MFD of the fiber.

As an example, SM400 single mode fiber has a mode field diameter (MFD) of ~Ø3 µm operating at 400 nm, while the MFD for SMF-28 Ultra single mode fiber operating at 1550 nm is Ø10.5 µm. The effective area for these fibers can be calculated as follows:

SM400 Fiber: Area = Pi x (MFD/2)2 = Pi x (1.5 µm)2 = 7.07 µm= 7.07 x 10-8 cm2

 SMF-28 Ultra Fiber: Area = Pi x (MFD/2)2 = Pi x (5.25 µm)2 = 86.6 µm= 8.66 x 10-7 cm2

To estimate the power level that a fiber facet can handle, the power density is multiplied by the effective area. Please note that this calculation assumes a uniform intensity profile, but most laser beams exhibit a Gaussian-like shape within single mode fiber, resulting in a higher power density at the center of the beam compared to the edges. Therefore, these calculations will slightly overestimate the power corresponding to the damage threshold or the practical safe level. Using the estimated power densities assuming a CW light source, we can determine the corresponding power levels as:

SM400 Fiber: 7.07 x 10-8 cm2 x 1 MW/cm2 = 7.1 x 10-8 MW = 71 mW (Theoretical Damage Threshold)
     7.07 x 10-8 cm2 x 250 kW/cm2 = 1.8 x 10-5 kW = 18 mW (Practical Safe Level)

SMF-28 Ultra Fiber: 8.66 x 10-7 cm2 x 1 MW/cm2 = 8.7 x 10-7 MW = 870 mW (Theoretical Damage Threshold)
           8.66 x 10-7 cm2 x 250 kW/cm2 = 2.1 x 10-4 kW = 210 mW (Practical Safe Level)

The effective area of a multimode (MM) fiber is defined by the core diameter, which is typically far larger than the MFD of an SM fiber. For optimal coupling, Thorlabs recommends focusing a beam to a spot roughly 70 - 80% of the core diameter. The larger effective area of MM fibers lowers the power density on the fiber end face, allowing higher optical powers (typically on the order of kilowatts) to be coupled into multimode fiber without damage.

Damage Mechanisms Related to Ferrule / Connector Termination


Click to Enlarge
Plot showing approximate power handling levels for single mode silica optical fiber with a termination. Each line shows the estimated power level due to a specific damage mechanism. The maximum power handling is limited by the lowest power level from all relevant damage mechanisms (indicated by a solid line).

Fibers terminated with optical connectors have additional power handling considerations. Fiber is typically terminated using epoxy to bond the fiber to a ceramic or steel ferrule. When light is coupled into the fiber through a connector, light that does not enter the core and propagate down the fiber is scattered into the outer layers of the fiber, into the ferrule, and the epoxy used to hold the fiber in the ferrule. If the light is intense enough, it can burn the epoxy, causing it to vaporize and deposit a residue on the face of the connector. This results in localized absorption sites on the fiber end face that reduce coupling efficiency and increase scattering, causing further damage.

For several reasons, epoxy-related damage is dependent on the wavelength. In general, light scatters more strongly at short wavelengths than at longer wavelengths. Misalignment when coupling is also more likely due to the small MFD of short-wavelength SM fiber that also produces more scattered light.

To minimize the risk of burning the epoxy, fiber connectors can be constructed to have an epoxy-free air gap between the optical fiber and ferrule near the fiber end face. Our high-power multimode fiber patch cables use connectors with this design feature.

Determining Power Handling with Multiple Damage Mechanisms

When fiber cables or components have multiple avenues for damage (e.g., fiber patch cables), the maximum power handling is always limited by the lowest damage threshold that is relevant to the fiber component.

As an illustrative example, the graph to the right shows an estimate of the power handling limitations of a single mode fiber patch cable due to damage to the fiber end face and damage via an optical connector. The total power handling of a terminated fiber at a given wavelength is limited by the lower of the two limitations at any given wavelength (indicated by the solid lines). A single mode fiber operating at around 488 nm is primarily limited by damage to the fiber end face (blue solid line), but fibers operating at 1550 nm are limited by damage to the optical connector (red solid line).

In the case of a multimode fiber, the effective mode area is defined by the core diameter, which is larger than the effective mode area for SM fiber. This results in a lower power density on the fiber end face and allows higher optical powers (on the order of kilowatts) to be coupled into the fiber without damage (not shown in graph). However, the damage limit of the ferrule / connector termination remains unchanged and as a result, the maximum power handling for a multimode fiber is limited by the ferrule and connector termination. 

Please note that these are rough estimates of power levels where damage is very unlikely with proper handling and alignment procedures. It is worth noting that optical fibers are frequently used at power levels above those described here. However, these applications typically require expert users and testing at lower powers first to minimize risk of damage. Even still, optical fiber components should be considered a consumable lab supply if used at high power levels.

Intrinsic Damage Threshold

In addition to damage mechanisms at the air / glass interface, optical fibers also display power handling limitations due to damage mechanisms within the optical fiber itself. These limitations will affect all fiber components as they are intrinsic to the fiber itself. Two categories of damage within the fiber are damage from bend losses and damage from photodarkening. 

Bend Losses
Bend losses occur when a fiber is bent to a point where light traveling in the core is incident on the core/cladding interface at an angle higher than the critical angle, making total internal reflection impossible. Under these circumstances, light escapes the fiber, often in a localized area. The light escaping the fiber typically has a high power density, which burns the fiber coating as well as any surrounding furcation tubing.

A special category of optical fiber, called double-clad fiber, can reduce the risk of bend-loss damage by allowing the fiber’s cladding (2nd layer) to also function as a waveguide in addition to the core. By making the critical angle of the cladding/coating interface higher than the critical angle of the core/clad interface, light that escapes the core is loosely confined within the cladding. It will then leak out over a distance of centimeters or meters instead of at one localized spot within the fiber, minimizing the risk of damage. Thorlabs manufactures and sells 0.22 NA double-clad multimode fiber, which boasts very high, megawatt range power handling.

Photodarkening
A second damage mechanism, called photodarkening or solarization, can occur in fibers used with ultraviolet or short-wavelength visible light, particularly those with germanium-doped cores. Fibers used at these wavelengths will experience increased attenuation over time. The mechanism that causes photodarkening is largely unknown, but several fiber designs have been developed to mitigate it. For example, fibers with a very low hydroxyl ion (OH) content have been found to resist photodarkening and using other dopants, such as fluorine, can also reduce photodarkening.

Even with the above strategies in place, all fibers eventually experience photodarkening when used with UV or short-wavelength light, and thus, fibers used at these wavelengths should be considered consumables.

Preparation and Handling of Optical Fibers

General Cleaning and Operation Guidelines
These general cleaning and operation guidelines are recommended for all fiber optic products. Users should still follow specific guidelines for an individual product as outlined in the support documentation or manual. Damage threshold calculations only apply when all appropriate cleaning and handling procedures are followed.

  1. All light sources should be turned off prior to installing or integrating optical fibers (terminated or bare). This ensures that focused beams of light are not incident on fragile parts of the connector or fiber, which can possibly cause damage.

  2. The power-handling capability of an optical fiber is directly linked to the quality of the fiber/connector end face. Always inspect the fiber end prior to connecting the fiber to an optical system. The fiber end face should be clean and clear of dirt and other contaminants that can cause scattering of coupled light. Bare fiber should be cleaved prior to use and users should inspect the fiber end to ensure a good quality cleave is achieved.

  3. If an optical fiber is to be spliced into the optical system, users should first verify that the splice is of good quality at a low optical power prior to high-power use. Poor splice quality may increase light scattering at the splice interface, which can be a source of fiber damage.

  4. Users should use low power when aligning the system and optimizing coupling; this minimizes exposure of other parts of the fiber (other than the core) to light. Damage from scattered light can occur if a high power beam is focused on the cladding, coating, or connector.

Tips for Using Fiber at Higher Optical Power
Optical fibers and fiber components should generally be operated within safe power level limits, but under ideal conditions (very good optical alignment and very clean optical end faces), the power handling of a fiber component may be increased. Users must verify the performance and stability of a fiber component within their system prior to increasing input or output power and follow all necessary safety and operation instructions. The tips below are useful suggestions when considering increasing optical power in an optical fiber or component.

  1. Splicing a fiber component into a system using a fiber splicer can increase power handling as it minimizes possibility of air/fiber interface damage. Users should follow all appropriate guidelines to prepare and make a high-quality fiber splice. Poor splices can lead to scattering or regions of highly localized heat at the splice interface that can damage the fiber.

  2. After connecting the fiber or component, the system should be tested and aligned using a light source at low power. The system power can be ramped up slowly to the desired output power while periodically verifying all components are properly aligned and that coupling efficiency is not changing with respect to optical launch power.

  3. Bend losses that result from sharply bending a fiber can cause light to leak from the fiber in the stressed area. When operating at high power, the localized heating that can occur when a large amount of light escapes a small localized area (the stressed region) can damage the fiber. Avoid disturbing or accidently bending fibers during operation to minimize bend losses.

  4. Users should always choose the appropriate optical fiber for a given application. For example, large-mode-area fibers are a good alternative to standard single mode fibers in high-power applications as they provide good beam quality with a larger MFD, decreasing the power density on the air/fiber interface.

  5. Step-index silica single mode fibers are normally not used for ultraviolet light or high-peak-power pulsed applications due to the high spatial power densities associated with these applications.


Please Give Us Your Feedback
 
Email Feedback On
(Optional)
Contact Me:
Your email address will NOT be displayed.
 
 
Please type the following key into the field to submit this form:
Click Here if you can not read the security code.
This code is to prevent automated spamming of our site
Thank you for your understanding.
  
 
Would this product be useful to you?   Little Use  1234Very Useful

Enter Comments Below:
 
Characters remaining  8000   
Posted Comments:
Poster:roemee817
Posted Date:2017-01-04 14:16:08.457
I have some questions about your product whose part number is SM980-5.8-125. I will use 1550 nm fiber. What is the maximum fiber input power available?? Thank you for reading me!
Poster:tfrisch
Posted Date:2017-01-04 09:02:46.0
Hello, thank you for contacting Thorlabs. The max power that can be coupled into a fiber depends on several factors including termination and the quality of the beam coupled. 300mW is a good rule of thumb for any fiber connector that may have an adhesive. For a bare cleaved fiber and a beam that is aligned with high coupling efficiency, a few watts should be achievable. Be sure coupling efficiency is high before power is increased. I will reach out to you directly about the details of what goes into that.
Poster:bnewell
Posted Date:2016-10-28 09:59:43.15
Hello, we use HI1060-100 optical fiber. We currently use a heated stripper, but we would like to understand if there are alternative methods that offer less risk of fiber damage. Would you be able to recommend any? Thank you.
Poster:tfrisch
Posted Date:2016-10-31 05:49:39.0
Hello, thank you for contacting Thorlabs. I have reached out to you directly about your applications.
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
SM980-5.8-125 Support Documentation
SM980-5.8-125Single Mode Optical Fiber, 980 - 1550 nm, Ø125 µm Cladding
$5.65
Per Meter
Volume Pricing
Today
SM980G80 Support Documentation
SM980G80Customer Inspired!Single Mode Optical Fiber, 980 - 1550 nm, Ø80 µm Cladding
$4.70
Per Meter
Volume Pricing
Today
HI1060-100 Support Documentation
HI1060-100100 m of HI1060 with Ø900 µm Jacket, Ø125 µm Cladding
$644.00
Today
HI1060-J9 Support Documentation
HI1060-J9HI1060 with Ø900 µm Jacket, Ø125 µm Cladding
$9.45
Per Meter
Volume Pricing
Today
1060XP Support Documentation
1060XPSingle Mode Optical Fiber, 980 - 1600 nm, Extra-High Performance, Ø125 µm Cladding
$4.95
Per Meter
Volume Pricing
Today
980HP Support Documentation
980HPSingle Mode Optical Fiber, 980 - 1600 nm, Ø125 µm Cladding
$4.90
Per Meter
Volume Pricing
Today

Single Mode Fiber: 1260 to 1650 nm

Stock Patch Cables Available with These Fibers
SMF-28 Ultra Fiber
1550BHP Fiber

Custom cables are also available. Click here for details.

Custom Patch Cables
Stock Single Mode Patch Cables

Features

  • Shipped from Stock
  • No Minimums
  • Fibers have Acrylate Coatings
  • SMF-28-100, SMF-28-1000, and SMF-28-J9 have Ø900 µm Hytrel Outer Jackets
  • CCC1310-J9 has a Ø900 µm PVC Outer Jacket
  • Exceptional Core/Clad Concentricity Specifications
  • 1550BHP Offers Tight Second Mode Cut-off Tolerances
  • SM1250G80, CCC1310-J9, and SM1500G80 Offer Enhanced Bend Insensitivity (See the Specs Tab for Information)
Item # Operating Wavelength Mode Field Diameter Cladding Coating Cut-Off Wavelength
SMF-28-J9 1260 - 1625 nm 9.2 ± 0.4 µm @ 1310 nm
10.4 ± 0.5 µm @ 1550 nm
125 ± 0.7 µm 242 ± 5 µm <1260 nm
CCC1310-J9 1260 - 1625 nm 8.6 ± 0.4 µm @ 1310 nm
9.7 ± 0.5 µm @ 1550 nm
125 ± 0.7 µm 242 ± 5 µm ≤1260 nm
1310BHP 1300 - 1625 nm 8.6 ± 0.5 µm @ 1310 nm
9.7 ± 0.5 µm @ 1550 nm
125 ± 1.0 µm 245 ± 15 µm 1260 ± 30 nm
SM1250G80 1310 - 1550 nm 8.2 - 9.9 µm @ 1310 nm 80 ± 1 µm 170 ± 10 µm 1150 - 1250 nm
1550BHP 1460 - 1620 nm 9.5 ± 0.5 µm @ 1550 nm 125 ± 1.0 µm 245 ± 15 µm 1400 ± 50 nm
SM1500G80 1520 - 1650 nm 6.0 - 6.8 µm @ 1550 nm 80 ± 1 µm 170 ± 10 µm 1350 - 1520 nm
Item # Short-Term Bend Radius Long-Term Bend Radius Attenuation (Max) NA Core Index Cladding Index
SMF-28-J9 - - ≤0.32 dB/km @ 1310 nm
≤0.18 dB/km @ 1550 nm
0.14 Propietarya Propietarya
CCC1310-J9 - - ≤0.35 dB/km @ 1310 nm
≤0.20 dB/km @ 1550 nm
0.14 1310 nm: 1.4670
1550 nm: 1.4677
-
1310BHP - - ≤0.5 dB/km @ 1310 nm & 1550 nm 0.13 Callb Callb
SM1250G80 ≥5 mm ≥12 mm (or 38 mm for 25 Year Life) ≤2 dB/km 0.11 - 0.13 1310 nm: 1.45094c
1550 nm: 1.44813c
1310 nm: 1.44680c
1550 nm: 1.44399c
1550BHP - - ≤0.5 dB/km @ 1550 nm 0.13 Callb Callb
SM1500G80 ≥5 mm ≥12 mm (or 38 mm for 25 Year Life) ≤0.5 dB/km 0.19 - 0.21 1550 nm: 1.45636d 1550 nm: 1.44399d
  • We regret that we cannot provide this proprietary information.
  • Please contact our Technical Support Staff to learn more about the refractive index of this fiber, as we are not permitted to publish this information on our website.
  • The indices provided are for an NA of 0.11.
  • The index provided is for an NA of 0.19.

Definition of the Mode Field Diameter

The mode field diameter (MFD) is one measure of the beam size of light propagating in a single mode fiber. It is a function of wavelength, core radius, and the refractive indices of the core and cladding. While much of the light in an optical fiber is trapped within the fiber core, a small fraction propagates in the cladding. For a Gaussian power distribution, the MFD is the diameter where the optical power is reduced to 1/e2 from its peak level.

Measurement of MFD
The measurement of MFD is accomplished by the Variable Aperture Method in the Far Field (VAMFF). An aperture is placed in the far field of the fiber output, and the intensity is measured. As successively smaller apertures are placed in the beam, the intensity levels are measured for each aperture; the data can then be plotted as power vs. the sine of the aperture half-angle (or the numerical aperture).

The MFD is then determined using Petermann's second definition, which is a mathematical model that does not assume a specific shape of power distribution. The MFD in the near field can be determined from this far-field measurement using the Hankel Transform.

Laser-Induced Damage in Silica Optical Fibers

The following tutorial details damage mechanisms relevant to unterminated (bare) fiber, terminated optical fiber, and other fiber components from laser light sources. These mechanisms include damage that occurs at the air / glass interface (when free-space coupling or when using connectors) and in the optical fiber itself. A fiber component, such as a bare fiber, patch cable, or fused coupler, may have multiple potential avenues for damage (e.g., connectors, fiber end faces, and the device itself). The maximum power that a fiber can handle will always be limited by the lowest limit of any of these damage mechanisms.

While the damage threshold can be estimated using scaling relations and general rules, absolute damage thresholds in optical fibers are very application dependent and user specific. Users can use this guide to estimate a safe power level that minimizes the risk of damage. Following all appropriate preparation and handling guidelines, users should be able to operate a fiber component up to the specified maximum power level; if no maximum is specified for a component, users should abide by the "practical safe level" described below for safe operation of the component. Factors that can reduce power handling and cause damage to a fiber component include, but are not limited to, misalignment during fiber coupling, contamination of the fiber end face, or imperfections in the fiber itself. For further discussion about an optical fiber’s power handling abilities for a specific application, please contact Thorlabs’ Tech Support.

Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Undamaged Fiber End
Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Damaged Fiber End

Damage at the Air / Glass Interface

There are several potential damage mechanisms that can occur at the air / glass interface. Light is incident on this interface when free-space coupling or when two fibers are mated using optical connectors. High-intensity light can damage the end face leading to reduced power handling and permanent damage to the fiber. For fibers terminated with optical connectors where the connectors are fixed to the fiber ends using epoxy, the heat generated by high-intensity light can burn the epoxy and leave residues on the fiber facet directly in the beam path.

Estimated Optical Power Densities on Air / Glass Interfacea
Type Theoretical Damage Thresholdb Practical Safe Levelc
CW
(Average Power)
~1 MW/cm2 ~250 kW/cm2
10 ns Pulsed
(Peak Power)
~5 GW/cm2 ~1 GW/cm2
  • All values are specified for unterminated (bare) silica fiber and apply for free space coupling into a clean fiber end face.
  • This is an estimated maximum power density that can be incident on a fiber end face without risking damage. Verification of the performance and reliability of fiber components in the system before operating at high power must be done by the user, as it is highly system dependent.
  • This is the estimated safe optical power density that can be incident on a fiber end face without damaging the fiber under most operating conditions.

Damage Mechanisms on the Bare Fiber End Face

Damage mechanisms on a fiber end face can be modeled similarly to bulk optics, and industry-standard damage thresholds for UV Fused Silica substrates can be applied to silica-based fiber. However, unlike bulk optics, the relevant surface areas and beam diameters involved at the air / glass interface of an optical fiber are very small, particularly for coupling into single mode (SM) fiber. therefore, for a given power density, the power incident on the fiber needs to be lower for a smaller beam diameter.

The table to the right lists two thresholds for optical power densities: a theoretical damage threshold and a "practical safe level". In general, the theoretical damage threshold represents the estimated maximum power density that can be incident on the fiber end face without risking damage with very good fiber end face and coupling conditions. The "practical safe level" power density represents minimal risk of fiber damage. Operating a fiber or component beyond the practical safe level is possible, but users must follow the appropriate handling instructions and verify performance at low powers prior to use.

Calculating the Effective Area for Single Mode and Multimode Fibers
The effective area for single mode (SM) fiber is defined by the mode field diameter (MFD), which is the cross-sectional area through which light propagates in the fiber; this area includes the fiber core and also a portion of the cladding. To achieve good efficiency when coupling into a single mode fiber, the diameter of the input beam must match the MFD of the fiber.

As an example, SM400 single mode fiber has a mode field diameter (MFD) of ~Ø3 µm operating at 400 nm, while the MFD for SMF-28 Ultra single mode fiber operating at 1550 nm is Ø10.5 µm. The effective area for these fibers can be calculated as follows:

SM400 Fiber: Area = Pi x (MFD/2)2 = Pi x (1.5 µm)2 = 7.07 µm= 7.07 x 10-8 cm2

 SMF-28 Ultra Fiber: Area = Pi x (MFD/2)2 = Pi x (5.25 µm)2 = 86.6 µm= 8.66 x 10-7 cm2

To estimate the power level that a fiber facet can handle, the power density is multiplied by the effective area. Please note that this calculation assumes a uniform intensity profile, but most laser beams exhibit a Gaussian-like shape within single mode fiber, resulting in a higher power density at the center of the beam compared to the edges. Therefore, these calculations will slightly overestimate the power corresponding to the damage threshold or the practical safe level. Using the estimated power densities assuming a CW light source, we can determine the corresponding power levels as:

SM400 Fiber: 7.07 x 10-8 cm2 x 1 MW/cm2 = 7.1 x 10-8 MW = 71 mW (Theoretical Damage Threshold)
     7.07 x 10-8 cm2 x 250 kW/cm2 = 1.8 x 10-5 kW = 18 mW (Practical Safe Level)

SMF-28 Ultra Fiber: 8.66 x 10-7 cm2 x 1 MW/cm2 = 8.7 x 10-7 MW = 870 mW (Theoretical Damage Threshold)
           8.66 x 10-7 cm2 x 250 kW/cm2 = 2.1 x 10-4 kW = 210 mW (Practical Safe Level)

The effective area of a multimode (MM) fiber is defined by the core diameter, which is typically far larger than the MFD of an SM fiber. For optimal coupling, Thorlabs recommends focusing a beam to a spot roughly 70 - 80% of the core diameter. The larger effective area of MM fibers lowers the power density on the fiber end face, allowing higher optical powers (typically on the order of kilowatts) to be coupled into multimode fiber without damage.

Damage Mechanisms Related to Ferrule / Connector Termination


Click to Enlarge
Plot showing approximate power handling levels for single mode silica optical fiber with a termination. Each line shows the estimated power level due to a specific damage mechanism. The maximum power handling is limited by the lowest power level from all relevant damage mechanisms (indicated by a solid line).

Fibers terminated with optical connectors have additional power handling considerations. Fiber is typically terminated using epoxy to bond the fiber to a ceramic or steel ferrule. When light is coupled into the fiber through a connector, light that does not enter the core and propagate down the fiber is scattered into the outer layers of the fiber, into the ferrule, and the epoxy used to hold the fiber in the ferrule. If the light is intense enough, it can burn the epoxy, causing it to vaporize and deposit a residue on the face of the connector. This results in localized absorption sites on the fiber end face that reduce coupling efficiency and increase scattering, causing further damage.

For several reasons, epoxy-related damage is dependent on the wavelength. In general, light scatters more strongly at short wavelengths than at longer wavelengths. Misalignment when coupling is also more likely due to the small MFD of short-wavelength SM fiber that also produces more scattered light.

To minimize the risk of burning the epoxy, fiber connectors can be constructed to have an epoxy-free air gap between the optical fiber and ferrule near the fiber end face. Our high-power multimode fiber patch cables use connectors with this design feature.

Determining Power Handling with Multiple Damage Mechanisms

When fiber cables or components have multiple avenues for damage (e.g., fiber patch cables), the maximum power handling is always limited by the lowest damage threshold that is relevant to the fiber component.

As an illustrative example, the graph to the right shows an estimate of the power handling limitations of a single mode fiber patch cable due to damage to the fiber end face and damage via an optical connector. The total power handling of a terminated fiber at a given wavelength is limited by the lower of the two limitations at any given wavelength (indicated by the solid lines). A single mode fiber operating at around 488 nm is primarily limited by damage to the fiber end face (blue solid line), but fibers operating at 1550 nm are limited by damage to the optical connector (red solid line).

In the case of a multimode fiber, the effective mode area is defined by the core diameter, which is larger than the effective mode area for SM fiber. This results in a lower power density on the fiber end face and allows higher optical powers (on the order of kilowatts) to be coupled into the fiber without damage (not shown in graph). However, the damage limit of the ferrule / connector termination remains unchanged and as a result, the maximum power handling for a multimode fiber is limited by the ferrule and connector termination. 

Please note that these are rough estimates of power levels where damage is very unlikely with proper handling and alignment procedures. It is worth noting that optical fibers are frequently used at power levels above those described here. However, these applications typically require expert users and testing at lower powers first to minimize risk of damage. Even still, optical fiber components should be considered a consumable lab supply if used at high power levels.

Intrinsic Damage Threshold

In addition to damage mechanisms at the air / glass interface, optical fibers also display power handling limitations due to damage mechanisms within the optical fiber itself. These limitations will affect all fiber components as they are intrinsic to the fiber itself. Two categories of damage within the fiber are damage from bend losses and damage from photodarkening. 

Bend Losses
Bend losses occur when a fiber is bent to a point where light traveling in the core is incident on the core/cladding interface at an angle higher than the critical angle, making total internal reflection impossible. Under these circumstances, light escapes the fiber, often in a localized area. The light escaping the fiber typically has a high power density, which burns the fiber coating as well as any surrounding furcation tubing.

A special category of optical fiber, called double-clad fiber, can reduce the risk of bend-loss damage by allowing the fiber’s cladding (2nd layer) to also function as a waveguide in addition to the core. By making the critical angle of the cladding/coating interface higher than the critical angle of the core/clad interface, light that escapes the core is loosely confined within the cladding. It will then leak out over a distance of centimeters or meters instead of at one localized spot within the fiber, minimizing the risk of damage. Thorlabs manufactures and sells 0.22 NA double-clad multimode fiber, which boasts very high, megawatt range power handling.

Photodarkening
A second damage mechanism, called photodarkening or solarization, can occur in fibers used with ultraviolet or short-wavelength visible light, particularly those with germanium-doped cores. Fibers used at these wavelengths will experience increased attenuation over time. The mechanism that causes photodarkening is largely unknown, but several fiber designs have been developed to mitigate it. For example, fibers with a very low hydroxyl ion (OH) content have been found to resist photodarkening and using other dopants, such as fluorine, can also reduce photodarkening.

Even with the above strategies in place, all fibers eventually experience photodarkening when used with UV or short-wavelength light, and thus, fibers used at these wavelengths should be considered consumables.

Preparation and Handling of Optical Fibers

General Cleaning and Operation Guidelines
These general cleaning and operation guidelines are recommended for all fiber optic products. Users should still follow specific guidelines for an individual product as outlined in the support documentation or manual. Damage threshold calculations only apply when all appropriate cleaning and handling procedures are followed.

  1. All light sources should be turned off prior to installing or integrating optical fibers (terminated or bare). This ensures that focused beams of light are not incident on fragile parts of the connector or fiber, which can possibly cause damage.

  2. The power-handling capability of an optical fiber is directly linked to the quality of the fiber/connector end face. Always inspect the fiber end prior to connecting the fiber to an optical system. The fiber end face should be clean and clear of dirt and other contaminants that can cause scattering of coupled light. Bare fiber should be cleaved prior to use and users should inspect the fiber end to ensure a good quality cleave is achieved.

  3. If an optical fiber is to be spliced into the optical system, users should first verify that the splice is of good quality at a low optical power prior to high-power use. Poor splice quality may increase light scattering at the splice interface, which can be a source of fiber damage.

  4. Users should use low power when aligning the system and optimizing coupling; this minimizes exposure of other parts of the fiber (other than the core) to light. Damage from scattered light can occur if a high power beam is focused on the cladding, coating, or connector.

Tips for Using Fiber at Higher Optical Power
Optical fibers and fiber components should generally be operated within safe power level limits, but under ideal conditions (very good optical alignment and very clean optical end faces), the power handling of a fiber component may be increased. Users must verify the performance and stability of a fiber component within their system prior to increasing input or output power and follow all necessary safety and operation instructions. The tips below are useful suggestions when considering increasing optical power in an optical fiber or component.

  1. Splicing a fiber component into a system using a fiber splicer can increase power handling as it minimizes possibility of air/fiber interface damage. Users should follow all appropriate guidelines to prepare and make a high-quality fiber splice. Poor splices can lead to scattering or regions of highly localized heat at the splice interface that can damage the fiber.

  2. After connecting the fiber or component, the system should be tested and aligned using a light source at low power. The system power can be ramped up slowly to the desired output power while periodically verifying all components are properly aligned and that coupling efficiency is not changing with respect to optical launch power.

  3. Bend losses that result from sharply bending a fiber can cause light to leak from the fiber in the stressed area. When operating at high power, the localized heating that can occur when a large amount of light escapes a small localized area (the stressed region) can damage the fiber. Avoid disturbing or accidently bending fibers during operation to minimize bend losses.

  4. Users should always choose the appropriate optical fiber for a given application. For example, large-mode-area fibers are a good alternative to standard single mode fibers in high-power applications as they provide good beam quality with a larger MFD, decreasing the power density on the air/fiber interface.

  5. Step-index silica single mode fibers are normally not used for ultraviolet light or high-peak-power pulsed applications due to the high spatial power densities associated with these applications.


Please Give Us Your Feedback
 
Email Feedback On
(Optional)
Contact Me:
Your email address will NOT be displayed.
 
 
Please type the following key into the field to submit this form:
Click Here if you can not read the security code.
This code is to prevent automated spamming of our site
Thank you for your understanding.
  
 
Would this product be useful to you?   Little Use  1234Very Useful

Enter Comments Below:
 
Characters remaining  8000   
Posted Comments:
No Comments Posted
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
SMF-28-100 Support Documentation
SMF-28-100100 m of SMF-28 Ultra with Ø900 µm Jacket, Ø125 µm Cladding
$52.75
Today
SMF-28-1000 Support Documentation
SMF-28-10001000 m of SMF-28 Ultra with Ø900 µm Jacket, Ø125 µm Cladding
$474.00
Today
SMF-28-J9 Support Documentation
SMF-28-J9SMF-28 Ultra with Ø900 µm Jacket, Ø125 µm Cladding
$2.30
Per Meter
Volume Pricing
Today
CCC1310-J9 Support Documentation
CCC1310-J91260 - 1625 nm Low Bend Loss Fiber with Ø900 µm Jacket, Ø125 µm Cladding
$2.30
Volume Pricing
Today
1310BHP Support Documentation
1310BHPSelect Cut-Off Single Mode Fiber, 1310 and 1550 nm, Ø125 µm Cladding
$4.90
Per Meter
Volume Pricing
Today
SM1250G80 Support Documentation
SM1250G80Customer Inspired!Single Mode Fiber, 0.11 - 0.13 NA, 1310 - 1550 nm, Ø80 µm
$4.70
Per Meter
Volume Pricing
Today
1550BHP Support Documentation
1550BHPSingle Mode Optical Fiber, 1460 - 1620 nm, Ø125 µm Cladding
$4.90
Per Meter
Volume Pricing
Today
SM1500G80 Support Documentation
SM1500G80Customer Inspired!Single Mode Optical Fiber, 0.19 - 0.21 NA, 1520 - 1650 nm, Ø80 µm
$4.70
Per Meter
Volume Pricing
Today

Single Mode Fiber: 1.7 to 2.3 µm

Stock Patch Cables Available with These Fibers
SM2000 Fiber
Item # Prefix Connectors Length
P1-2000-FC FC/PC to FC/PC 1 or 2 m
P3-2000-FC FC/APC to FC/APC 2 m
P5-2000-PCAPC FC/PC to FC/APC 1 m
P2-2000-PCSMA FC/PC to SMA 1 m
P1-2000AR-2 AR-Coated (1700 - 2100 nm) FC/PC to Uncoated FC/PC 2 m
P5-2000AR-2 AR-Coated (1700 - 2100 nm) FC/PC to Uncoated FC/APC 2 m
P4-2000AR-2 AR-Coated (1700 - 2100 nm) FC/APC to Uncoated FC/PC 2 m
P3-2000AR-2 AR-Coated (1700 - 2100 nm) FC/APC to Uncoated FC/APC 2 m

Custom cables are also available. Click here for details.

Custom Patch Cables
Stock Single Mode Patch Cables

Features

  • Shipped from Stock
  • No Minimums
  • Ge-Doped Silica Core, Pure Silica Cladding, and a UV Cured Acrylate Coating
  • Large Core for Coupling 2 µm Light
  • NA Compatible with Corning's SMF-28 Fiber
  • Exceptional Core/Clad Concentricity Specifications
  • Low Bend Losses (See Specs Tab)
Item #Operating WavelengthMFDCore DiameterCladding DiameterBufferCut-Off Wavelength
SM2000 1700 - 2300 nm 13  ± 1 µm @ 1996 nm 11 ± 1 µm 125 ± 1 µm 245 ± 10 µm 1700 nm
Item #Cladding NoncircularityCore-Clad Concentricity Typical AttenuationNACore IndexCladding Index
SM2000 ≤2% <0.8 µm 2.3 µm: 250 dB/km (0.25 dB/m)
1.9 µm: 20 dB/km (0.02 dB/m)
0.11 2 µm: 1.4436 2 µm: 1.4381
SM2000 and SMF28 Bend losses
Click to Enlarge

Click for Raw Data
This plot contains the measured attenuation for our SM2000 fiber across the single mode wavelength range (1700 nm - 2300 nm).
SM2000 Power
Click to Enlarge

Click for Raw Data
This plot contains the measured attenuation for a single loop of our single mode SM2000 fiber at nine different bend radii. The shaded region in the plot denotes the single mode wavelength range (1.7 - 2.3 µm).
SM2000 and SMF28 Bend losses
Click to Enlarge

Using a 1996 nm source and a Ø30 mm mandrel, the bend losses (dB) of the SM2000 and SMF-28e+ fibers were measured for each turn of the fiber around the mandrel. Based on the measurement, the loss/turn of the SM2000 fiber is ~0.08 dB. For the SMF-28e+ fiber, the loss/turn is ~3 dB. The SM2000 fiber is much less sensitive to bending than SMF-28e+ fiber.
SM2000 Refractive Index Profile
        Click to Enlarge

Definition of the Mode Field Diameter

The mode field diameter (MFD) is one measure of the beam size of light propagating in a single mode fiber. It is a function of wavelength, core radius, and the refractive indices of the core and cladding. While much of the light in an optical fiber is trapped within the fiber core, a small fraction propagates in the cladding. For a Gaussian power distribution, the MFD is the diameter where the optical power is reduced to 1/e2 from its peak level.

Measurement of MFD
The measurement of MFD is accomplished by the Variable Aperture Method in the Far Field (VAMFF). An aperture is placed in the far field of the fiber output, and the intensity is measured. As successively smaller apertures are placed in the beam, the intensity levels are measured for each aperture; the data can then be plotted as power vs. the sine of the aperture half-angle (or the numerical aperture).

The MFD is then determined using Petermann's second definition, which is a mathematical model that does not assume a specific shape of power distribution. The MFD in the near field can be determined from this far-field measurement using the Hankel Transform.

Laser-Induced Damage in Silica Optical Fibers

The following tutorial details damage mechanisms relevant to unterminated (bare) fiber, terminated optical fiber, and other fiber components from laser light sources. These mechanisms include damage that occurs at the air / glass interface (when free-space coupling or when using connectors) and in the optical fiber itself. A fiber component, such as a bare fiber, patch cable, or fused coupler, may have multiple potential avenues for damage (e.g., connectors, fiber end faces, and the device itself). The maximum power that a fiber can handle will always be limited by the lowest limit of any of these damage mechanisms.

While the damage threshold can be estimated using scaling relations and general rules, absolute damage thresholds in optical fibers are very application dependent and user specific. Users can use this guide to estimate a safe power level that minimizes the risk of damage. Following all appropriate preparation and handling guidelines, users should be able to operate a fiber component up to the specified maximum power level; if no maximum is specified for a component, users should abide by the "practical safe level" described below for safe operation of the component. Factors that can reduce power handling and cause damage to a fiber component include, but are not limited to, misalignment during fiber coupling, contamination of the fiber end face, or imperfections in the fiber itself. For further discussion about an optical fiber’s power handling abilities for a specific application, please contact Thorlabs’ Tech Support.

Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Undamaged Fiber End
Power Handling Limitations Imposed by Optical Fiber
Click to Enlarge

Damaged Fiber End

Damage at the Air / Glass Interface

There are several potential damage mechanisms that can occur at the air / glass interface. Light is incident on this interface when free-space coupling or when two fibers are mated using optical connectors. High-intensity light can damage the end face leading to reduced power handling and permanent damage to the fiber. For fibers terminated with optical connectors where the connectors are fixed to the fiber ends using epoxy, the heat generated by high-intensity light can burn the epoxy and leave residues on the fiber facet directly in the beam path.

Estimated Optical Power Densities on Air / Glass Interfacea
Type Theoretical Damage Thresholdb Practical Safe Levelc
CW
(Average Power)
~1 MW/cm2 ~250 kW/cm2
10 ns Pulsed
(Peak Power)
~5 GW/cm2 ~1 GW/cm2
  • All values are specified for unterminated (bare) silica fiber and apply for free space coupling into a clean fiber end face.
  • This is an estimated maximum power density that can be incident on a fiber end face without risking damage. Verification of the performance and reliability of fiber components in the system before operating at high power must be done by the user, as it is highly system dependent.
  • This is the estimated safe optical power density that can be incident on a fiber end face without damaging the fiber under most operating conditions.

Damage Mechanisms on the Bare Fiber End Face

Damage mechanisms on a fiber end face can be modeled similarly to bulk optics, and industry-standard damage thresholds for UV Fused Silica substrates can be applied to silica-based fiber. However, unlike bulk optics, the relevant surface areas and beam diameters involved at the air / glass interface of an optical fiber are very small, particularly for coupling into single mode (SM) fiber. therefore, for a given power density, the power incident on the fiber needs to be lower for a smaller beam diameter.

The table to the right lists two thresholds for optical power densities: a theoretical damage threshold and a "practical safe level". In general, the theoretical damage threshold represents the estimated maximum power density that can be incident on the fiber end face without risking damage with very good fiber end face and coupling conditions. The "practical safe level" power density represents minimal risk of fiber damage. Operating a fiber or component beyond the practical safe level is possible, but users must follow the appropriate handling instructions and verify performance at low powers prior to use.

Calculating the Effective Area for Single Mode and Multimode Fibers
The effective area for single mode (SM) fiber is defined by the mode field diameter (MFD), which is the cross-sectional area through which light propagates in the fiber; this area includes the fiber core and also a portion of the cladding. To achieve good efficiency when coupling into a single mode fiber, the diameter of the input beam must match the MFD of the fiber.

As an example, SM400 single mode fiber has a mode field diameter (MFD) of ~Ø3 µm operating at 400 nm, while the MFD for SMF-28 Ultra single mode fiber operating at 1550 nm is Ø10.5 µm. The effective area for these fibers can be calculated as follows:

SM400 Fiber: Area = Pi x (MFD/2)2 = Pi x (1.5 µm)2 = 7.07 µm= 7.07 x 10-8 cm2

 SMF-28 Ultra Fiber: Area = Pi x (MFD/2)2 = Pi x (5.25 µm)2 = 86.6 µm= 8.66 x 10-7 cm2

To estimate the power level that a fiber facet can handle, the power density is multiplied by the effective area. Please note that this calculation assumes a uniform intensity profile, but most laser beams exhibit a Gaussian-like shape within single mode fiber, resulting in a higher power density at the center of the beam compared to the edges. Therefore, these calculations will slightly overestimate the power corresponding to the damage threshold or the practical safe level. Using the estimated power densities assuming a CW light source, we can determine the corresponding power levels as:

SM400 Fiber: 7.07 x 10-8 cm2 x 1 MW/cm2 = 7.1 x 10-8 MW = 71 mW (Theoretical Damage Threshold)
     7.07 x 10-8 cm2 x 250 kW/cm2 = 1.8 x 10-5 kW = 18 mW (Practical Safe Level)

SMF-28 Ultra Fiber: 8.66 x 10-7 cm2 x 1 MW/cm2 = 8.7 x 10-7 MW = 870 mW (Theoretical Damage Threshold)
           8.66 x 10-7 cm2 x 250 kW/cm2 = 2.1 x 10-4 kW = 210 mW (Practical Safe Level)

The effective area of a multimode (MM) fiber is defined by the core diameter, which is typically far larger than the MFD of an SM fiber. For optimal coupling, Thorlabs recommends focusing a beam to a spot roughly 70 - 80% of the core diameter. The larger effective area of MM fibers lowers the power density on the fiber end face, allowing higher optical powers (typically on the order of kilowatts) to be coupled into multimode fiber without damage.

Damage Mechanisms Related to Ferrule / Connector Termination


Click to Enlarge
Plot showing approximate power handling levels for single mode silica optical fiber with a termination. Each line shows the estimated power level due to a specific damage mechanism. The maximum power handling is limited by the lowest power level from all relevant damage mechanisms (indicated by a solid line).

Fibers terminated with optical connectors have additional power handling considerations. Fiber is typically terminated using epoxy to bond the fiber to a ceramic or steel ferrule. When light is coupled into the fiber through a connector, light that does not enter the core and propagate down the fiber is scattered into the outer layers of the fiber, into the ferrule, and the epoxy used to hold the fiber in the ferrule. If the light is intense enough, it can burn the epoxy, causing it to vaporize and deposit a residue on the face of the connector. This results in localized absorption sites on the fiber end face that reduce coupling efficiency and increase scattering, causing further damage.

For several reasons, epoxy-related damage is dependent on the wavelength. In general, light scatters more strongly at short wavelengths than at longer wavelengths. Misalignment when coupling is also more likely due to the small MFD of short-wavelength SM fiber that also produces more scattered light.

To minimize the risk of burning the epoxy, fiber connectors can be constructed to have an epoxy-free air gap between the optical fiber and ferrule near the fiber end face. Our high-power multimode fiber patch cables use connectors with this design feature.

Determining Power Handling with Multiple Damage Mechanisms

When fiber cables or components have multiple avenues for damage (e.g., fiber patch cables), the maximum power handling is always limited by the lowest damage threshold that is relevant to the fiber component.

As an illustrative example, the graph to the right shows an estimate of the power handling limitations of a single mode fiber patch cable due to damage to the fiber end face and damage via an optical connector. The total power handling of a terminated fiber at a given wavelength is limited by the lower of the two limitations at any given wavelength (indicated by the solid lines). A single mode fiber operating at around 488 nm is primarily limited by damage to the fiber end face (blue solid line), but fibers operating at 1550 nm are limited by damage to the optical connector (red solid line).

In the case of a multimode fiber, the effective mode area is defined by the core diameter, which is larger than the effective mode area for SM fiber. This results in a lower power density on the fiber end face and allows higher optical powers (on the order of kilowatts) to be coupled into the fiber without damage (not shown in graph). However, the damage limit of the ferrule / connector termination remains unchanged and as a result, the maximum power handling for a multimode fiber is limited by the ferrule and connector termination. 

Please note that these are rough estimates of power levels where damage is very unlikely with proper handling and alignment procedures. It is worth noting that optical fibers are frequently used at power levels above those described here. However, these applications typically require expert users and testing at lower powers first to minimize risk of damage. Even still, optical fiber components should be considered a consumable lab supply if used at high power levels.

Intrinsic Damage Threshold

In addition to damage mechanisms at the air / glass interface, optical fibers also display power handling limitations due to damage mechanisms within the optical fiber itself. These limitations will affect all fiber components as they are intrinsic to the fiber itself. Two categories of damage within the fiber are damage from bend losses and damage from photodarkening. 

Bend Losses
Bend losses occur when a fiber is bent to a point where light traveling in the core is incident on the core/cladding interface at an angle higher than the critical angle, making total internal reflection impossible. Under these circumstances, light escapes the fiber, often in a localized area. The light escaping the fiber typically has a high power density, which burns the fiber coating as well as any surrounding furcation tubing.

A special category of optical fiber, called double-clad fiber, can reduce the risk of bend-loss damage by allowing the fiber’s cladding (2nd layer) to also function as a waveguide in addition to the core. By making the critical angle of the cladding/coating interface higher than the critical angle of the core/clad interface, light that escapes the core is loosely confined within the cladding. It will then leak out over a distance of centimeters or meters instead of at one localized spot within the fiber, minimizing the risk of damage. Thorlabs manufactures and sells 0.22 NA double-clad multimode fiber, which boasts very high, megawatt range power handling.

Photodarkening
A second damage mechanism, called photodarkening or solarization, can occur in fibers used with ultraviolet or short-wavelength visible light, particularly those with germanium-doped cores. Fibers used at these wavelengths will experience increased attenuation over time. The mechanism that causes photodarkening is largely unknown, but several fiber designs have been developed to mitigate it. For example, fibers with a very low hydroxyl ion (OH) content have been found to resist photodarkening and using other dopants, such as fluorine, can also reduce photodarkening.

Even with the above strategies in place, all fibers eventually experience photodarkening when used with UV or short-wavelength light, and thus, fibers used at these wavelengths should be considered consumables.

Preparation and Handling of Optical Fibers

General Cleaning and Operation Guidelines
These general cleaning and operation guidelines are recommended for all fiber optic products. Users should still follow specific guidelines for an individual product as outlined in the support documentation or manual. Damage threshold calculations only apply when all appropriate cleaning and handling procedures are followed.

  1. All light sources should be turned off prior to installing or integrating optical fibers (terminated or bare). This ensures that focused beams of light are not incident on fragile parts of the connector or fiber, which can possibly cause damage.

  2. The power-handling capability of an optical fiber is directly linked to the quality of the fiber/connector end face. Always inspect the fiber end prior to connecting the fiber to an optical system. The fiber end face should be clean and clear of dirt and other contaminants that can cause scattering of coupled light. Bare fiber should be cleaved prior to use and users should inspect the fiber end to ensure a good quality cleave is achieved.

  3. If an optical fiber is to be spliced into the optical system, users should first verify that the splice is of good quality at a low optical power prior to high-power use. Poor splice quality may increase light scattering at the splice interface, which can be a source of fiber damage.

  4. Users should use low power when aligning the system and optimizing coupling; this minimizes exposure of other parts of the fiber (other than the core) to light. Damage from scattered light can occur if a high power beam is focused on the cladding, coating, or connector.

Tips for Using Fiber at Higher Optical Power
Optical fibers and fiber components should generally be operated within safe power level limits, but under ideal conditions (very good optical alignment and very clean optical end faces), the power handling of a fiber component may be increased. Users must verify the performance and stability of a fiber component within their system prior to increasing input or output power and follow all necessary safety and operation instructions. The tips below are useful suggestions when considering increasing optical power in an optical fiber or component.

  1. Splicing a fiber component into a system using a fiber splicer can increase power handling as it minimizes possibility of air/fiber interface damage. Users should follow all appropriate guidelines to prepare and make a high-quality fiber splice. Poor splices can lead to scattering or regions of highly localized heat at the splice interface that can damage the fiber.

  2. After connecting the fiber or component, the system should be tested and aligned using a light source at low power. The system power can be ramped up slowly to the desired output power while periodically verifying all components are properly aligned and that coupling efficiency is not changing with respect to optical launch power.

  3. Bend losses that result from sharply bending a fiber can cause light to leak from the fiber in the stressed area. When operating at high power, the localized heating that can occur when a large amount of light escapes a small localized area (the stressed region) can damage the fiber. Avoid disturbing or accidently bending fibers during operation to minimize bend losses.

  4. Users should always choose the appropriate optical fiber for a given application. For example, large-mode-area fibers are a good alternative to standard single mode fibers in high-power applications as they provide good beam quality with a larger MFD, decreasing the power density on the air/fiber interface.

  5. Step-index silica single mode fibers are normally not used for ultraviolet light or high-peak-power pulsed applications due to the high spatial power densities associated with these applications.


Please Give Us Your Feedback
 
Email Feedback On
(Optional)
Contact Me:
Your email address will NOT be displayed.
 
 
Please type the following key into the field to submit this form:
Click Here if you can not read the security code.
This code is to prevent automated spamming of our site
Thank you for your understanding.
  
 
Would this product be useful to you?   Little Use  1234Very Useful

Enter Comments Below:
 
Characters remaining  8000   
Posted Comments:
No Comments Posted
Based on your currency / country selection, your order will ship from Newton, New Jersey  
+1 Qty Docs Part Number - Universal Price Available / Ships
SM2000 Support Documentation
SM2000Customer Inspired!Single Mode Optical Fiber, 1.7-2.3 µm, Ø125 µm Cladding
$15.10
Per Meter
Volume Pricing
Today
Log In  |   My Account  |   Contact Us  |   Careers  |   Privacy Policy  |   Home  |   FAQ  |   Site Index
Regional Websites:East Coast US | Europe | Asia | China | Japan
Copyright 1999-2017 Thorlabs, Inc.
Sales: 1-973-300-3000
Technical Support: 1-973-300-3000


High Quality Thorlabs Logo 1000px:Save this Image