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Total Internal Reflection in an Optical Fiber

Guiding Light in an Optical Fiber

Optical fibers are part of a broader class of optical components known as waveguides that utilize total internal reflection (TIR) in order to confine and guide light within a solid or liquid structure. Optical fibers, in particular, are used in numerous applications; common examples include telecommunications, spectroscopy, illumination, and sensors.

One of the more common glass (silica) optical fibers uses a structure known as a step-index fiber, which is shown in the image to the right. Step-index fibers have an inner core made from a material with a refractive index that is higher than the surrounding cladding layer. Within the fiber, a critical angle of incidence exists such that light will reflect off the core/cladding interface rather than refract into the surrounding medium. To fulfill the conditions for TIR in the fiber, the angle of incidence of light launched into the fiber must be less than a certain angle, which is defined as the acceptance angle, θ_acc. Snell's law can be used to calculate this angle:

where n_core is the refractive index of the fiber core, n_clad is the refractive index of the fiber cladding, n is the refractive index of the outside medium, θ_crit is the critical angle, and θ_acc is the acceptance half-angle of the fiber. The numerical aperture (NA) is a dimensionless quantity used by fiber manufacturers to specify the acceptance angle of an optical fiber and is defined as:

In step-index fibers with a large core (multimode), the NA can be calculated directly using this equation. The NA can also be determined experimentally by tracing the far-field beam profile and measuring the angle between the center of the beam and the point at which the beam intensity is 5% of the maximum; however, calculating the NA directly provides the most accurate value.

Number of Modes in an Optical Fiber

Each potential path that light propagates through in an optical fiber is known as a guided mode of the fiber. Depending on the physical dimensions of the core/cladding regions, refractive index, and wavelength, anything from one to thousands of modes can be supported within a single optical fiber. The two most commonly manufactured variants are single mode fiber (which supports a single guided mode) and multimode fiber (which supports a large number of guided modes). In a multimode fiber, lower-order modes tend to confine light spatially in the core of the fiber; higher-order modes, on the other hand, tend to confine light spatially near the core/cladding interface.

Using a few simple calculations, it is possible to estimate the number of modes (single mode or multimode) supported by an optical fiber. The normalized optical frequency, also known as the V-number, is a dimensionless quantity that is proportional to the free space optical frequency but is normalized to guiding properties of an optical fiber. The V-number is defined as:

where V is the normalized frequency (V-number), a is the fiber core radius, and λ is the free space wavelength. Multimode fibers have very large V-numbers; for example, a Ø50 µm core, 0.39 NA multimode fiber at a wavelength of 1.5 µm has a V-number of 40.8.

For multimode fiber, which has a large V-number, the number of modes supported is approximated using the following relationship.

In the example above of the Ø50 µm core, 0.39 NA multimode fiber, it supports approximately 832 different guided modes that can all travel simultaneously through the fiber.

Single mode fibers are defined with a V-number cut-off of V < 2.405, which represents the point at which light is coupled only into the fiber's fundamental mode. To meet this condition, a single mode fiber has a much smaller core size and NA compared to a multimode fiber at the same wavelength. One example of this, SMF-28 Ultra single mode fiber, has a nominal NA of 0.14 and an Ø8.2 µm core at 1550 nm, which results in a V-number of 2.404.

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Attenuation Due to Macrobend Loss

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Attenuation Due to Microbend Loss

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Beam profile measurement of FT200EMT multimode fiber and a former generation M565F1 LED (replaced by the M565F3) showing light guided in the cladding rather than the core of the fiber.

Sources of Attenuation

Loss within an optical fiber, also referred to as attenuation, is characterized and quantified in order to predict the total transmitted power lost within a fiber optic setup. The sources of these losses are typically wavelength dependent and range from the material used in the fiber itself to bending of the fiber. Common sources of attenuation are detailed below:

Absorption
Because light in a standard optical fiber is guided via a solid material, there are losses due to absorption as light propagates through the fiber. Standard fibers are manufactured using fused silica and are optimized for transmission from 1300 nm to 1550 nm. At longer wavelengths (>2000 nm), multi-phonon interactions in fused silica cause significant absorption. Fluoride glasses such as ZrF₄ and InF₃ are used in manufacturing Mid-IR optical fibers primarily because they exhibit lower loss at these wavelengths. ZrF₄ and InF₃ fibers have a multi-phonon edge of ~3.6 µm and ~4.6 µm, respectively.

Contaminants in the fiber also contribute to the absorption loss. One example of an undesired impurity is water molecules that are trapped in the glass of the optical fiber, which will absorb light around 1300 nm and 2.94 µm. Since telecom signals and some lasers operate in that same region, any water molecules present in the fiber will attenuate the signal significantly.

The concentration of ions in the fiber glass is often controlled by manufacturers to tune the transmission/attenuation properties of a fiber. For example, hydroxyl ions (OH-) are naturally present in silica and absorb light in the NIR-IR spectrum. Therefore, fibers with low-OH content are preferred for transmission at telecom wavelengths. On the other hand, fibers with high-OH content typically exhibit increased transmission at UV wavelengths and thus may be preferred by users interested in applications such as fluorescence or UV-VIS spectroscopy. 

Scattering
For the majority of fiber optics applications, light scattering is a source of loss that occurs when light encounters a change in the refractive index of the medium. These changes can be extrinsic, caused by impurities, particulates, or bubbles; or intrinsic, caused by fluctuations in the glass density, composition, or phase state. Scattering is inversely related to the wavelength of light, so scattering loss becomes significant at shorter wavelengths such as the UV or blue regions of the spectrum. Using proper fiber cleaning, handling, and storage procedures may minimize the presence of impurities on tips of fibers that cause large scattering losses.

Bending Loss
Losses that occur due to changes in the external and internal geometry of an optical fiber are known as bending loss. These are usually separated into two categories: macrobending loss and microbending loss.

Macrobend loss is typically associated with the physical bending of an optical fiber; for example, rolling it in a tight coil. As shown in the image to the right, guided light is spatially distributed within the core and cladding regions of the fiber. When a fiber is bent at a radius, light near the outer radius of the bend cannot maintain the same spatial mode profile without exceeding the speed of light. Instead, the energy is lost to the surroundings as radiation. For a large bend radius, the losses associated with bending are small; however, at bend radii smaller than the recommended bend radius of a fiber, bend losses become very significant. For short periods of time, optical fibers can be operated at a small bend radius; however, for long-term storage, the bend radius should be larger than the recommended value. Use proper storage conditions (temperature and bend radius) to reduce the likelihood of permanently damaging the fiber; the FSR1 Fiber Storage Reel is designed to minimize high bend loss.

Microbend loss arises from changes in the internal geometry of the fiber, particularly the core and cladding layers. These random variations (i.e., bumps) in the fiber structure disturb the conditions needed for total internal reflection, causing propagating light to couple into a non-propagating mode that leaks from the fiber (see the image to the right for details). Unlike macrobend loss, which is controlled by the bend radius, microbend loss occurs due to permanent defects in the fiber that are created during fiber manufacturing.

Cladding Modes
While most light in a multimode fiber is guided via TIR within the core of the fiber, higher-order modes that guide light within both the core and cladding layer, because of TIR at the cladding and coating/buffer interface, can also exist. This results in what is known as a cladding mode. An example of this can be seen in the beam profile measurement to the right, which shows cladding modes with a higher intensity in the cladding than in the core of the fiber. These modes can be non-propagating (i.e., they do not fulfill the conditions for TIR) or they can propagate over a significant length of fiber. Because cladding modes are typically higher-order, they are a source of loss in the presence of fiber bending and microbending defects. Cladding modes are also lost when connecting two fibers via connectors as they cannot be easily coupled between optical fibers.

Cladding modes may be undesired for some applications (e.g., launching into free space) because of their effect on the beam spatial profile. Over long fiber lengths, these modes will naturally attenuate. For short fiber lengths (<10 m), one method for removing cladding modes from a fiber is to use a mandrel wrap at a radius that removes cladding modes while keeping the desired propagating modes.

Launch Conditions

Underfilled Launch Condition
For a large multimode fiber which accepts light over a wide NA, the condition of the light (e.g., source type, beam diameter, NA) coupled into the fiber can have a significant effect on performance. An underfilled launch condition occurs when the beam diameter and NA of light at the coupling interface are smaller than the core diameter and NA of the fiber. A common example of this is launching a laser source into a large multimode fiber. As seen in the diagram and beam profile measurement below, underfilled launches tend to concentrate light spatially in the center of the fiber, filling lower-order modes preferentially over higher-order modes. As a result, they are less sensitive to macrobend losses and do not have cladding modes. The measured insertion loss for an underfilled launch tends to be lower than typical, with a higher power density in the core of the fiber. 

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Diagram illustrating an underfilled launch condition (left) and a beam profile measurement using a FT200EMT multimode fiber (right).

Overfilled Launch Condition
Overfilled launches are defined by situations where the beam diameter and NA at the coupling interface are larger than the core diameter and NA of the fiber. One method to achieve this is by launching light from an LED source into a small multimode fiber. An overfilled launch completely exposes the fiber core and some of the cladding to light, enabling the filling of lower- and higher-order modes equally (as seen in the images below) and increasing the likelihood of coupling into cladding modes of the fiber. This increased percentage of higher-order modes means that overfilled fibers are more sensitive to bending loss. The measured insertion loss for an overfilled launch tends to be higher than typical, but results in an overall higher output power compared to an underfilled fiber launch. 

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Diagram illustrating an overfilled launch condition (left) and a beam profile measurement using a FT200EMT multimode fiber (right).

There are advantages and disadvantages to underfilled or overfilled launch conditions, depending on the needs of the intended application. For measuring the baseline performance of a multimode fiber, Thorlabs recommends using a launch condition where the beam diameter is 70-80% of the fiber core diameter. Over short distances, an overfilled fiber has more output power; however, over long distances (>10 - 20 m) the higher-order modes that more susceptible to attenuation will disappear. 

Optogenetics Selection Guide

Thorlabs offers a wide range of optogenetics components; the compatibility of these products in select standard configurations is discussed in detail here. Please contact Technical Support for assistance with items outside the scope of this guide, including custom fiber components for optogenetics.

Single-Site Stimulation

One Light Source to One Cannula Implant

The most straightforward method for in vivo light stimulation of a specimen is to use a single fiber optic with a single LED light source. The single wavelength LED is powered by an LED driver, and then the illumination output is fiber-coupled into a patch cable, which connects to the implanted cannula. See the graphics and expandable compatibility tables below for the necessary patch cables and cannulae to create this setup. To choose the appropriate LED and driver, see below or the full web presentation.

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Click to See Ø1.25 mm (LC) Ferrule Compatible Patch Cables, Cannulae, and Interconnects

Component Selection Table (Click Links for Item Description Popup)
Fiber Type		FG105LCA	FG200UCC	FT200EMT	FP200URT	FT400EMT	FP400URT
Fiber Type Specs	Core Diameter	105 µm	200 µm			400 µm
	Wavelength Range	400 - 2400 nm	250 - 1200 nm	400 - 2200 nm	300 - 1200 nm	400 - 2200 nm	300 - 1200 nm
	NA	0.22	0.22	0.39	0.50	0.39	0.50
Patch Cablesb	Standard FC/PC Input	M61L01	M86L005 M86L01	M83L01 MR83L01	M73L01	M99L01	M127L01
	Standard SMA905 Input	M63L01	M87L005 M87L01	M89L01 MR89L01	M95L01	M98L01	M125L01
	Rotary Joint FC/PC Input	-	-	RJPFL2	-	RJPFL4	-
	Rotary Joint SMA905 Input	-	-	RJPSL2	-	RJPSL4	-
Compatible Mating Sleeve/Interconnect		ADAL1, ADAL3, or ADAL4-5
Fiber Optic Cannulaec	Ceramic 6.4 mm Long Ferrule	CFMLC21L02 CFMLC21L05 CFMLC21L10 CFMLC21L20 CFMLC21U-20	CFMLC22L02 CFMLC22L05 CFMLC22L10 CFMLC22L20 CFMLC22U-20	CFMLC12L02 CFMLC12L05 CFMLC12L10 CFMLC12L20 CFMLC12U-20	CFMLC52L02 CFMLC52L05 CFMLC52L10 CFMLC52L20 CFMLC52U-20	CFMLC14L02 CFMLC14L05 CFMLC14L10 CFMLC14L20 CFMLC14U-20	CFMLC15L02 CFMLC15L05 CFMLC15L10 CFMLC15L20
	Diffuser Tip (Ceramic 6.4 mm Long Ferrule)	-	-	CFDSB02 CFDSB05 CFDSB10 CFDSB20	-	-	-
	Ceramic 10.5 mm Long Ferrule	-	CFMXA02 CFMXA05 CFMXA10 CFMXA20	CFMXB02 CFMXB05 CFMXB10 CFMXB20	CFMXC02 CFMXC05 CFMXC10 CFMXC20	-	CFMXD02 CFMXD05 CFMXD10 CFMXD20
	Stainless Steel 6.4 mm Long Ferrule	CFML21L02 CFML21L05 CFML21L10 CFML21L20 CFML21U-20	CFML22L02 CFML22L05 CFML22L10 CFML22L20 CFML22U-20	CFML12L02 CFML12L05 CFML12L10 CFML12L20 CFML12U-20	CFML52L02 CFML52L05 CFML52L10 CFML52L20 CFML52U-20	CFML14L02 CFML14L05 CFML14L10 CFML14L20 CFML14U-20	CFML15L02 CFML15L05 CFML15L10 CFML15L20
Items are compatible with each other when they are comprised of the same fiber type and listed in the same column. Patch cables for single source to single implant applications are highlighted in green above. Choose a patch cable with an input that matches your light source. Available cannulae are highlighted in orange of the table above. Cannulae within the same column are interchangeable.

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Click to See Ø2.5 mm (FC) Ferrule Compatible Patch Cables, Cannulae, and Interconnects

Component Selection Table (Click Links for Item Description Popup)
Fiber Type		FG200UCC	FT200EMT	FP200URT	FT300EMT	FT400EMT	FP400URT
Fiber Type Specs	Core Diameter	200 µm			300 µm	400 µm
	Wavelength Range	250 - 1200 nm	400 - 2200 nm	300 - 1200 nm	400 - 2200 nm	400 - 2200 nm	300 - 1200 nm
	NA	0.22	0.39	0.50	0.39	0.39	0.50
Patch Cablesb	Standard FC/PC Input	M80L005 M80L01	M81L005 M81L01 MR81L01	M104L01	M56L005 M56L01	M82L005 M82L01	M128L01
	Standard SMA905 Input	M84L005 M84L01	M77L005 M77L01 MR77L01	M106L01	M58L005 M58L01	M79L005 M79L01	M126L01
	Rotary Joint FC/PC Input	-	RJAFF2 RJPFF2	-	-	RJPFF4	-
	Rotary Joint SMA905 Input	-	RJASF2 RJPSF2	-	-	RJPSF4	-
Compatible Mating Sleeve/Interconnect		ADAF1, ADAF2, or ADAF4-5
Fiber Optic Cannulaec	Ceramic 10.5 mm Long Ferrule	CFMC22L02 CFMC22L05 CFMC22L10 CFMC22L20 CFMC22U-20	CFMC12L02 CFMC12L05 CFMC12L10 CFMC12L20 CFMC12U-20	CFMC52L02 CFMC52L05 CFMC52L10 CFMC52L20 CFMC52U-20	CFMC13L02 CFMC13L05 CFMC13L10 CFMC13L20	CFMC14L02 CFMC14L05 CFMC14L10 CFMC14L20 CFMC14U-20	CFMC54L02 CFMC54L05 CFMC54L10 CFMC54L20
	Stainless Steel 12.7 mm Long Ferrule	CFM22L02 CFM22L05 CFM22L10 CFM22L20 CFM22U-20	CFM12L02 CFM12L05 CFM12L10 CFM12L20 CFM12U-20	CFM52L02 CFM52L05 CFM52L10 CFM52L20 CFM52U-20	CFM13L02 CFM13L05 CFM13L10 CFM13L20	CFM14L02 CFM14L05 CFM14L10 CFM14L20 CFM14U-20	CFM15L02 CFM15L05 CFM15L10 CFM15L20
Items are compatible with each other when they are comprised of the same fiber type and listed in the same column. Patch cables for single source to single implant applications are highlighted in green above. Choose a patch cable with an input that matches your light source. Available cannulae are highlighted in orange of the table above. Cannulae within the same column are interchangeable.

Multilateral Stimulation

The ability to accurately and simultaneously direct light to multiple locations within a specimen is desired for many types of optogenetics experiments. For example, bilateral stimulation techniques typically target neurons in two spatially separated regions in order to induce a desired behavior. In more complex experiments involving the simultaneous inhibition and stimulation of neurons, delivering light of two different monochromatic wavelengths within close proximity enables the user to perform these experiments without implanting multiple cannulae, which can increase stress on the specimen.

Multilateral stimulation can be achieved with several different configurations depending on the application requirements. The sections below illustrate examples of different configurations using Thorlabs' optogenetics products.

Option 1: One Light Source to Two Cannula Implants Using Rotary Joint Splitter

Thorlabs' RJ2 1x2 Rotary Joint Splitter is designed for optogenetics applications and is used to split light from a single input evenly between two outputs. The rotary joint interface allows connected patch cables to freely rotate, reducing the risk of fiber damage caused by a moving specimen. See the graphic and compatibility table below for the necessary cables and cannulae to create this setup. For LEDs and drivers, see below or the full web presentation.

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Click to See Ø1.25 mm (LC) Ferrule Components Recommended for Use with RJ2 Rotary Joint Splitter

Component Selection Table (Click Links for Item Description Popup)
Common Fiber Properties
Fiber Properties	Core Diameter	200 µm			400 µm
	Wavelength Rangea	400 - 700 nm	400 - 700 nm	400 - 700 nm	400 - 700 nm	400 - 700 nm
	NA	0.22	0.39	0.50	0.39	0.50
Input Patch Cablesb	Standard FC/PC Connectors	M122L01 M122L02 M122L05	M72L01 M72L02 M72L05	M123L01 M123L02	M74L01 M74L02 M74L05	M124L01 M124L02
	Hybrid SMA905 to FC/PC	M36L01	M75L01 M75L02	M129L01 M129L02	M76L01 M76L02	M131L01 M131L02
Rotary Joint		RJ2
Output Patch Cables	FC/PC to Ø1.25 mm (LC) Ferrule	M86L005 M86L01	M83L01 MR83L01	M73L01	M99L01	M127L01
Compatible Mating Sleeve/Interconnect		ADAL1, ADAL3, or ADAL4-5
Fiber Optic Cannulaec	Ceramic 6.4 mm Long Ferrule	CFMLC22L02 CFMLC22L05 CFMLC22L10 CFMLC22L20 CFMLC22U-20	CFMLC12L02 CFMLC12L05 CFMLC12L10 CFMLC12L20 CFMLC12U-20	CFMLC52L02 CFMLC52L05 CFMLC52L10 CFMLC52L20 CFMLC52U-20	CFMLC14L02 CFMLC14L05 CFMLC14L10 CFMLC14L20 CFMLC14U-20	CFMLC15L02 CFMLC15L05 CFMLC15L10 CFMLC15L20
	Diffuser Tip (Ceramic 6.4 mm Long Ferrule)	-	CFDSB02 CFDSB05 CFDSB10 CFDSB20	-	-	-
	Ceramic 10.5 mm Long Ferrule	CFMXA02 CFMXA05 CFMXA10 CFMXA20	CFMXB02 CFMXB05 CFMXB10 CFMXB20	CFMXC02 CFMXC05 CFMXC10 CFMXC20	-	CFMXD02 CFMXD05 CFMXD10 CFMXD20
	Stainless Steel 6.4 mm Long Ferrule	CFML22L02 CFML22L05 CFML22L10 CFML22L20 CFML22U-20	CFML12L02 CFML12L05 CFML12L10 CFML12L20 CFML12U-20	CFML52L02 CFML52L05 CFML52L10 CFML52L20 CFML52U-20	CFML14L02 CFML14L05 CFML14L10 CFML14L20 CFML14U-20	CFML15L02 CFML15L05 CFML15L10 CFML15L20
Products in each column can be used with each other over the indicated wavelength range and is limited by the operating range of the RJ2 Rotary Joint Splitter. Individual products may be used outside this range; see product information for detailed specifications. Use a standard FC/PC patch cable to connect to an FC/PC-terminated light source. SMA905 to FC/PC hybrid patch cables should be used to connect to an SMA905-terminated light source. Available cannulae are highlighted in orange of the table above. Cannulae within the same column are interchangeable.

Click for Detials

Click to See Ø2.5 mm (FC) Ferrule Components Recommended for Use with RJ2 Rotary Joint Splitter

Component Selection Table (Click Links for Item Description Popup)
Common Fiber Properties
Fiber Properties	Core Diameter	200 µm			300 µm	400 µm
	Wavelength Rangea	400 - 700 nm	400 - 700 nm	400 - 700 nm	400 - 700 nm	400 - 700 nm	400 - 700 nm
	NA	0.22	0.39	0.50	0.39	0.39	0.50
Input Patch Cables	Standard FC/PC Connectors	M122L01 M122L02 M122L05	M72L01 M72L02 M72L05	M123L01 M123L02	M56L005 M56L01	M74L01 M74L02 M74L05	M124L01 M124L02
	Hybrid SMA905 to FC/PC	M36L01	M75L01 M75L02	M129L01 M129L02	M58L005 M58L01	M76L01 M76L02	M131L01 M131L02
Rotary Joint		RJ2
Output Patch Cables	FC/PC to Ø2.5 mm (FC) Ferrule	M80L005 M80L01	M81L005 M81L01 MR81L01	M104L01	M56L005 M56L01	M82L005 M82L01	M128L01
Compatible Mating Sleeve/Interconnect		ADAF1, ADAF2, or ADAF4-5
Fiber Optic Cannulaec	Ceramic 10.5 mm Long Ferrule	CFMC22L02 CFMC22L05 CFMC22L10 CFMC22L20 CFMC22U-20	CFMC12L02 CFMC12L05 CFMC12L10 CFMC12L20 CFMC12U-20	CFMC52L02 CFMC52L05 CFMC52L10 CFMC52L20 CFMC52U-20	CFMC13L02 CFMC13L05 CFMC13L10 CFMC13L20	CFMC14L02 CFMC14L05 CFMC14L10 CFMC14L20 CFMC14U-20	CFMC54L02 CFMC54L05 CFMC54L10 CFMC54L20
	Stainless Steel 12.7 mm Long Ferrule	CFM22L02 CFM22L05 CFM22L10 CFM22L20 CFM22U-20	CFM12L02 CFM12L05 CFM12L10 CFM12L20 CFM12U-20	CFM52L02 CFM52L05 CFM52L10 CFM52L20 CFM52U-20	CFM13L02 CFM13L05 CFM13L10 CFM13L20	CFM14L02 CFM14L05 CFM14L10 CFM14L20 CFM14U-20	CFM15L02 CFM15L05 CFM15L10 CFM15L20
Products in each column can be used with each other over the indicated wavelength range and is limited by the operating range of the RJ2 Rotary Joint Splitter. Individual products may be used outside this range; see product information for detailed specifications. Use a standard FC/PC patch cable to connect to an FC/PC-terminated light source. SMA905 to FC/PC hybrid patch cables should be used to connect to an SMA905-terminated light source. Available cannulae are highlighted in orange of the table above. Cannulae within the same column are interchangeable.

Option 2: One or Two Light Sources to Two Cannula Implants

If the intent is for one LED source to connect to two cannulae for simultaneous light modulation, then a bifurcated fiber bundle can be used to split the light from the LED into each respective cannula. For dual wavelength stimulation (mixing two wavelengths in a single cannula) or a more controlled split ratio between cannula, one can use a multimode coupler to connect one or two LEDs to the cannulae. If one cable end is left unused, the spare coupler cable end may be terminated by a light trap. See the graphic and compatibility table below for the necessary cables and cannulae to create this setup. For LEDs and drivers, see below or the full web presentation.

Click on Each Component Below for More Information

Option 3: One Light Sources to Seven Cannula Implants

If the intent is for one LED source to connect to seven cannulae for simultaneous light modulation, then a 1-to-7 fiber bundle can be used to split the light from the LED into each respective cannula. See the graphic and compatibility table below for the necessary cables and cannulae to create this setup. For LEDs and drivers, see below or the full web presentation.

Click on Each Component Below for More Information

 

Two Light Sources into One Dual-Core Cannula Implant

For bilateral stimulation applications where the two cannulas need to be placed in close proximity (within ~1 mm), Thorlabs offers dual-core patch cables and cannulae that are designed for this specific application. Each core is driven by a separate light source, enabling users to stimulate and/or supress nerve cells in the same region of the specimen. See the graphic and compatibility table below for the necessary cables and cannulae to create this setup. For LEDs and drivers, see below or the full web presentation.

Click on Each Component for More Information

Illumination

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M405F1

Fiber-Coupled LEDs and Drivers

Our fiber-coupled LEDs are ideal light sources for optogenetics applications. They feature a variety of wavelength choices and a convenient interconnection to optogenetics patch cables. Thorlabs offers fiber-coupled LEDs with nominal wavelengths ranging from 280 nm to 1050 nm. See the table to the right for the LEDs with the most popular wavelengths for optogenetics. A table of compatible LED drivers can be viewed by clicking below.

Click to See Compatible LED Drivers

Compatible Driversa	UPLEDb	LEDD1Bc	DC2200b	DC4100b,d,e	DC4104b,d,e
Click Photos to Enlarge
Main Driver Features	USB-Controlled	Very Compact Footprint 60 mm x 73 mm x 104 mm (W x H x D)	Touchscreen Interface with Internal and External Options for Pulsed and Modulated LED Operation	4 Channelsd	4 Channelsd
LED Driver Current Output (Max)	1.2 A	1.2 A	LED1 Terminal: 10.0 A LED2 Terminal: 2.0 Af	1.0 A per Channel	1.0 A per Channel
LED Driver Forward Voltage (Max)	8 V	12 V	50 V	5 V	5 V
Modulation Frequency	-	0 to 5 kHz (External)	20 to 100 kHz (Internal)h DC to 250 kHz (External)g,h	0 to 100 kHz (External)h Simultaneous Across all Channels	0 to 100 kHz (External)h Independently Controlled Channels
External Control Interface(s)	USB 2.0	Analog (BNC)	USB 2.0 and Analog (BNC)	USB 2.0 and Analog (BNC)	USB 2.0 and Analog (8-Pin)
EEPROM Compatible: Reads Out LED Data for LED Settings		-
LCD Display	-	-

• Click on the item number link to view the complete presentation for each controller.
• Automatically limits to LED's max current via EEPROM readout.
• The preferred power supply (single channel or hub-based) depends on the end user's application and whether you already own compatible power supplies. To that end and in keeping with Thorlabs' green initiative, we do not ship the LEDD1B bundled with a power supply. This avoids the cost and inconvenience of receiving an unwanted single-channel supply if a hub-based system (Item # KCH301 or KCH601) would be more appropriate.
• The DC4100 and DC4104 can power and control up to four LEDs simultaneously when used with the DC4100-HUB. The fiber-coupled LEDs on this page all require the DC4100-HUB when used with the DC4100 or DC4104.
• These LED drivers have a maximum forward voltage rating of 5 V and can provide a maximum current of 1000 mA. As a result, they cannot be used to drive LEDs which have forward voltage ratings greater than 5 V. LEDs with maximum current ratings higher than 1.0 A can be driven using this driver, but will not reach full power.
• The fiber-coupled LEDs sold above are compatible with the LED2 Terminal.
• Small Signal Bandwidth: Modulation not exceeding 20% of full scale current. The driver accepts other waveforms, but the maximum frequency will be reduced.
• The M565F3 and M595F2 LEDs produce light by stimulating emission from phosphor, which limits their modulation frequency range. These LEDs may not turn off completely when modulated above 10 kHz at duty cycles below 50%.