FiberPort Collimators / Couplers
|Click to Enlarge
FiberPort on HCP Post Mount used to Collimate Light from a Single Mode Fiber
- 5 Degrees of Freedom plus Rotational Adjustment
- Micropositioning Alignment for Collimation or Coupling
- FC/PC, FC/APC, and SMA Versions
- FC/PC and FC/APC Versions Accept Both 2.1 mm Wide Key
and 2.0 mm Narrow Key Connectors
- PAF-SMA FiberPorts are Designed for SMA 905 Connectors
- Available with Either an Aspheric or Achromatic Lens
- Suitable for Single Mode, Multimode, and Polarization-Maintaining (PM) Fiber
Thorlabs' compact, ultra-stable FiberPort micropositioners provide an easy-to-use platform for coupling light into and out of optical fibers. This device enables alignment to an FC/PC-, FC/APC-, or SMA-terminated fiber with six directional adjustments. The compact size combined with the ultra-stable alignment, which is maintained over time, makes the FiberPort an ideal solution for fiber coupling or collimation.
Five Degrees of Freedom (Plus Bulkhead Rotation)
While holding the connector and fiber stationary, the built-in lens can be aligned with five degrees of freedom: linear alignment of the lens in the x and y, and angular alignment for tip and tilt, plus z adjusment using the tip and tilt controls simultaneously. In addition, the locking screws on the front plate can be loosened to enable rotation of the bulkhead for PM fiber alignment. The lens adjustment and bulkhead rotation provide a total of six degrees of freedom. After alignment is complete, a locking setscrew can be tightened to secure the position. Please contact Tech Support for complete instructions regarding bulkhead adjustment.
Fiber Patch Cables for Fiberports
We recommend using FiberPorts with our AR-coated single mode or multimode fiber optic patch cables for both coupling and collimating applications. These cables feature an antireflective coating on one fiber end for increased transmission and improved return loss at the fiber to free space interface. These cables are available with an AR-coated FC/PC (SM), FC/APC (SM), or SMA (MM) connector. Alternatively, our large selection of standard fiber patch cables can also be used.
Lens Selection Example - Choosing a FiberPort for Fiber Coupling
The example presented here details the steps needed to ensure proper selection of a FiberPort to match the requirements of a particular fiber. For specific recommendations, please contact Technical Support.
Collimated Beam Diameter Prior to Lens: Ø3 mm
Wavelength: 633 nm
The specifications for the P1-630A-FC-2, 630 nm, FC/PC single mode patch cable indicate that the 1/e2 mode field diameter (MFD) is 4.3 μm at 633 nm. The MFD should equal the diffraction-limited spot size Øspot, which is given by the following equation:
Here, f is the focal length of the lens, λ is the wavelength of the input light, and D is the 1/e2 diameter of collimated beam incident on the lens. Solving for the desired focal length of the collimating lens yields:
Thorlabs offers a large selection of FiberPorts. You'll note that the FiberPort with a focal length closest to 16 mm has a focal length of 15.4 mm (Item # PAF-X-15-B), while also meeting the requirements for fiber connector and antireflection coating range. This FiberPort also has a clear aperture that is larger than the collimated beam diameter. Therefore, this is the best option given the initial parameters (i.e., a P1-630A-FC-2 single mode fiber and a collimated beam diameter of 3 mm). Remember, for optimum coupling the spot size of the focused beam must be less than the MFD of the single mode fiber. As a result, if a FiberPort is not available that provides an exact match, then choose the FiberPort with a focal length that is shorter than the calculation above yields. Alternatively, if the clear aperture of the lens is large enough, the beam can be expanded before the lens, which has the result of reducing the spot size of the focused beam.
Please note that the specified NA is the NA of the lens, not the required numerical aperture of the fiber you are using. As long as the lens NA is smaller than the NA of your fiber, you should be able to couple light. For best results, Thorlabs recommends using the equations above when choosing a FiberPort.
Thorlabs offers models with our A (350-700 nm*), B (600-1050 nm), C (1050-1600 nm), or D (1800-2400 nm) AR-coatings. These models may be used with single mode, multimode, and PM fibers terminated with FC/PC, FC/APC, or SMA connectors. Care should be taken in selecting a FiberPort to make sure the correct fiber/connector/FiberPort combination is selected. If you need assistance, please contact tech support at your local office.
Aspheric vs. Achromatic FiberPort Performance
Fiberports are available with either Aspheric or Achromatic Doublet Lenses. For applications requiring collimation of multiple visible wavelengths, the Achromatic FiberPorts are ideal. The achromatic design of the PAFA series of FiberPorts utilizes cemented doublets. These doublets minimize chromatic aberrations when coupling or collimating either a broadband light source or multiple wavelengths. The small focal length shifts experienced by an achromatic doublet allow the FiberPort to be used over a broad wavelength range without needing realignment (see below).
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This graph compares the performance of an achromatic doublet to an aspheric lens when a collimated beam is focused onto a fiber, such as the case with our FiberPort couplers. The achromatic doublet provides a small spot size on the fiber over a large wavelength range, while the aspheric lens offers a small spot size only over a narrow range.
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This graph plots the focal length shift of an aspheric lens (in PAFX-5-A) and a similar focal length achromatic doublet (in PAFA-X-4-A). The focal shift experienced by the aspheric lens is an order of magnitude larger than that of the achromatic doublet.
The FiberPort is a six degree of freedom fiber collimator and coupler (5-axis plus rotation). It uses a movable lens as the alignment mechanism while holding the fiber stationary. This provides an extremely stable and repeatable platform for coupling and collimating. All adjustments are coupled.
(Click to Enlarge)
The FiberPort consists of a body, a Magnetic Lens Cell (MLC) adhered to a tilt plate, and a bulkhead with fiber connector. The bulkhead is locked onto the FiberPort body by three flat head screws and the clamp plate. By loosening the flat head screws, the fiber bulkhead can be rotated freely.
The MLC adheres to the tilt plate, which can be adjusted in Z/q/j (Axial, Tip, Tilt) using the three socket head cap screws (SCHS). The plunger screws provide counterforce against the SCHS. The Z (optical axis) translation range is ± 0.4 mm for a given position of the plunge screws. The plunge screws can translate the + extreme of the travel range in the Z direction over a distance of 2 mm.
Additionally, the MLC can be translated in X-Y using the setscrews in the side of the fiberport body. The MLC rests on a leaf spring, and the X-Y screws push the cell against the leaf spring. A third setscrew behind the leaf spring can be used for locking. The travel range of the aspheric lens in the X and Y directions is ± 0.7 mm but when the FiberPort is used in a standard collimation/coupling application only a small portion of this translation range is used.
Location of Screws on the FiberPort
Please refer to the Operation tab for full operating instructions.
The X-Y lens adjustment screws are located on the outer diameter of the FiberPort body at the 9 o’clock and the 12 o’clock positions (in the photo below). The three plunger screws provide counterforce for the tilt plate. The three socket head cap screws (SHCS) provide the Z/q/j adjustments for the FiberPort. The three SHCS and the X-Y screws are the only screws that are normally used in the alignment of the FiberPort. However, the plunge screws can be used to adjust the tension on the tilt plate if needed. Also, the three flat head screws on the face of the FiberPort hold the clamp plate and bulkhead in place. By loosening these screws, the bulkhead can be rotated a full 360° and secured at any angle for PM applications. This is a coarse adjustment, however.
Location of Adjustment and Mounting Screws as Viewed from the Fiber Bulkhead Side (Click to Enlarge)
The locking screw is located on the outer diameter of the FiberPort body at the 4:30 position. The locking screw is not installed when the FiberPort is shipped but is included in the package. The locking screw is only used after the FiberPort is aligned. NOTE: Locking is not necessary in most applications and can affect coupling.
|Part ||Screw Size||Head Size (Hex)|
|Mounting Plate Attachment Screws||2-56||5/64"|
|X, Y, Z, Tip & Tilt|
Socket Head Screws
|Flat Head Screws||2-56||0.050"|
Collimating Out of a Fiber
- Attach a connectorized fiber source to the bulkhead of the FiberPort and examine the output.
- Adjust the X-Y screws to center the output beam in the tilt plate aperture. It is important to maintain the X-Y screws in a position neither too tight or loose at all times or they may not function properly.
- Trace the beam away from the FiberPort to check for collimation (see diagram to the right).
- For a converging beam (beam comes to a focus): The lens is too far away from the fiber. Alternately turn the SHCS (socket head cap screws) clockwise in small, equal increments. Be sure to adjust all screws in equal increments.
- For a diverging beam (beam diameter continually increases): The lens is too close to the fiber. Alternately turn the SHCS counter clockwise in small, equal increments. Be sure to adjust all screws in equal increments.
- Check the beam path and adjust the X-Y screws as needed to re-center the beam in the output aperture.
- Use progressively smaller adjustments until collimation is achieved and the desired beam centration is obtained. Do not force the screws past their normal operating range, if collimation is not easily achieved please contact Tech Support for assistance.
Coupling into a Fiber
- If possible, collimate light out of the FiberPort first (see Collimating out of Fiber above). This will put the lens close to the correct position to start coupling.
- In order to launch a free-space beam into the FiberPort effectively, it is essential that the incoming beam path be aligned with the fiber axis of the FiberPort. The diagram to the right illustrates a simple technique that can be implemented to achieve this alignment.
First, place two irises (set to the same height off the table) as shown in the figure to the right. Adjust mirror 1 (M1) until the beam passes through the center of Iris 1, then adjust M2 to align the beam through the center of Iris 2. Iris 1 may need to be opened at this stage to allow the beam to pass through to Iris 2 during the initial part of alignment. Repeat this process iteratively until the beam is centered through both Iris 1 and Iris 2.
- Place the FiberPort after Iris 2. Centering the input beam on the lens aperture of the FiberPort can be accomplished by affixing a target to the tilt plate in front of the lens. Make adjustments to the FiberPort’s position until the beam is visibly centered on the FiberPort aperture. The FiberPort can be mounted on to a HCP bracket mount in order to adjust its position.
Once the beam is centered, light should be clearly visible exiting the back of the FiberPort (with no fiber attached). Move the FiberPort body to make sure the beam is not visually clipped.
- Make sure the tip of the fiber is clean as this will maximize the amount of light coupled into the fiber. Once light is passing through the FiberPort, attach a multimode (MM) fiber (50 – 100 μm core) to the FiberPort, which will make the initial alignment process easier rather than coupling directly into a singlemode (SM) fiber.
- Attach an optical detector to the end of the fiber not connected to the FiberPort and monitor the output signal. An optical detector has a faster response time than a power meter, and thus may be more helpful for fiberport alignment. Steps 2 and 3 should ensure that enough light is coupled into the fiber in order to detect an output signal at this stage. If you do not have any measurable power, repeat steps 2 and 3.
- Use the X and Y adjustment screws to maximize the output signal. These adjustments are extremely sensitive. Small adjustments here translate to large coupling changes. The X and Y adjustments are coupled, so finding the maximum signal is an iterative process between the X and Y adjustments. Once the XY maximum is achieved, only VERY SMALL adjustments are needed. It is important to maintain the X-Y screws in a position neither too tight or loose at all times or they may not function properly.
- Monitor and maximize the output signal while making small, equal adjustments in Z/q/j positioning socket head cap screws (SHCS). This will allow the lens to move in the Z direction without altering the tip/tilt. Be sure to adjust the SHCS in equal increments.
NOTE: in order to determine which way to adjust the screws, unscrew the fiber connector from the bulkhead and monitor the output as the fiber is retracted from the bulkhead. If the power increases, then the lens needs to move further away from the fiber, and if it decreases then the lens still has to move closer to the fiber. (Turn the SCHS clockwise to move the lens closer to the fiber, and counterclockwise to move the lens farther from the fiber.)
- Start at any SHCS on the face of the FiberPort and make very small adjustments to get a maximum in the output signal.
- Move in a clockwise or counterclockwise direction to the next SHCS and make a similarly small adjustment.
- Continue in the same direction with the final SHCS, and again make an equal adjustment.
- After adjusting the SHCS, the signal may be lower that before the adjustment. Re-adjustment of the XY screws in the next step will show the increase in signal power.
- Repeat step 6 (XY adjustment) to reach an absolute maximum signal. Note that adjusting the XY screws may involve losing the signal, and then finding the maximum again. Adjust the X and Y screws iteratively to find an absolute maximum.
As the coupling efficiency increases, the magnitude of the adjustments will get smaller and smaller. If you intend to couple into an SM fiber, switch the MM fiber to an SM fiber at this point (once there is good coupling into the MM fiber after steps 5 and 6). It will be necessary to repeat steps 6 - 8 with the SM fiber in place to maximize the coupling.
NOTE: When coupling into SM fiber, even the smallest adjustments can drastically affect the coupling. When adjusting the SHCS be aware that by simply monitoring the power of the output signal, one can get stuck in a local maxima and never achieve best coupling. The ideal procedure is to make a small EQUAL adjustment in each of the SHCS in the chosen direction and only monitor the power once all the screws have been adjusted. Usually, one will see a drop in power once the 2nd screw is adjusted but then a large increase in power when the 3rd screw is adjusted, or when the XY screws are adjusted.
If you are using PM fiber, you can rotate the bulkhead to align the axis if needed. Please see Chapter 1 for more information on how to adjust the FiberPort.
FiberPort to FiberPort on a Single-Axis Fiberbench
- Assemble the FiberBench with both ports on the FiberBench facing each other as shown on the right.
- Collimate beam from input FiberPort: Attach an optical fiber to the input FiberPort in order to launch light into the FiberBench. Adjust the three SHCS screws in a near equal amount so the “Z” positioning is fine tuned to collimate the beam out of the fiber (see Chapter 5). It may only require very small adjustment.
- Center beam on output FiberPort: Once good collimation is achieved, use slight (quarter or eighth) turns of the SHCS to steer the beam to the center of the other FiberPort. If this adjustment is not enough, DO NOT adjust the screws any more. Instead, set them back to the previous position which gave good collimation (from step 2) and this time use the X-Y adjustment screws to move the lens in X-Y to steer the beam.
- Collimate and center other FiberPort: Repeat steps 2 and 3 for the other FiberPort, launching light backward through the output fiber.
- Beam Waist at Center: In order to maximize the coupling of light between the FiberPorts, place the waist of the beam at the center between the two FiberPorts.
- Use multimode fiber for coarse alignment: To align the FiberBench, start with multimode (50 – 100 µm core) fiber (if you have one) on the output port. The large core allows for easy coupling and good practice for the feel of the fiberport and which types of adjustments translate to coupling. This also helps to understand how quickly one can go out of alignment. NOTE: It does not help to use multimode fiber on the input port.
- Check output power: Connect the output fiber to a suitable detector in order to determine and monitor the power coupled into the output fiber, and the quality of the alignment. Some power should be present from steps 2 – 4 at this stage (possibly only 10 – 250 nW). If there is no measurable power, repeat steps 2 – 4 again.
- Fine-tune coupling: Once you have a measurable signal from the output fiber, you can further improve and fine tune the alignment/coupling by making adjustments and monitoring the power level on the detector. See section on fiber coupling.
- Switch to SM Fiber: Once the alignment is optimized, you can switch to using SM fiber on the output FiberPort. You may need to repeat step 3 to optimize the coupling efficiency.
Locking the FiberPort
Most applications DO NOT require locking.
If you are leaving the FiberPort on a table, it does not need to be locked. Screw on the black end cap to minimize unauthorized alignment changes. Typically, an aligned FiberPort can be hand carried and moved without alignment changes. Alignment can be lost in the locking process. For situations where the FiberPort can undergo large vibrations or shock, such as shipping, we recommend locking or potting the FiberPort. Locking the FiberPort is an iterative process requiring patience. The locking screw pushes the cell firmly against the X & Y screws. Alignment will be lost if the locking screw is tightened quickly.
When locking the position of the LMC using the procedure below, monitor the position of the beam if the FiberPort is being used as a collimator. If the FiberPort is being used to couple light into a fiber, attach a suitable optical detector to the output end of the fiber and monitor the output signal of the detector during the locking process. In either case, make sure that the locking process does not change the alignment of the LMC.
- Carefully thread the small locking screw into the FiberPort at the 7:30 o’clock position on the outer diameter.
- As you slowly tighten the locking screw, adjust the X-Y screws as required to maintain the alignment. DO NOT TORQUE DOWN ANY OF THE SCREWS. Applying too much pressure with the screws can permanently damage the magnet/lens assembly, the 0-80 screws, and/or destroy the alignment. When the X, Y, and locking screws are just snug, the lens is locked in place.
- To prevent accidental changes in Z/q/j, carefully tighten the plunger screws with the small size hex wrench. Make minor adjustments to the SHCS as necessary to maintain the alignment of the LMC. DO NOT TORQUE DOWN ANY OF THE SCREWS.
- If optimal alignment is lost when locking, first loosen the locking screw two full turns, then loosen the plunger screws ¼ turn each. The less the plunger screws have to travel to be locked the better. Now adjust the X-Y screws to regain optimal alignment. Repeat the steps 2 and 3 above.
- Screw the black end cap on to discourage any further adjustment of the alignment screws.
Fiber Collimator Selection Guide
Click on the collimator type or photo to view more information about each type of collimator.
|Fixed FC, APC, or SMA Fiber Collimators||These fiber collimation packages are pre-aligned to collimate light from an FC/PC-, FC/APC-, or SMA-connectorized fiber. Each collimation package is factory aligned to provide diffraction-limited performance at one of six wavelengths: 405, 543, 633, 780, 1064, 1310, or 1550 nm. Although it is possible to use the collimator at detuned wavelengths, they will only perform optimally at the design wavelength due to chromatic aberration, which causes the effective focal length of the spheric lens to have a wavelength dependence.|
|Air-Spaced Doublet, Large Beam Collimators||For large beam diameters (Ø6.6 - Ø8.5 mm), Thorlabs offers FC/PC, SMA, and FC/APC air-spaced doublet collimators. These collimation packages are pre-aligned at the factory to collimate a laser beam propagating from the tip of an FC or SMA conectorized fiber and provide diffraction-limited performance at the design wavelength. |
|Adjustable Fiber Collimators||These snap-on collimators are designed to connect onto the end of an FC/PC or FC/APC connector and contain an AR-coated aspheric lens. The distance between the aspheric lens and the tip of the FC-terminated fiber can be adjusted to compensate for focal length changes or to recollimate the beam at the wavelength and distance of interest. |
|FiberPorts||These compact, ultra-stable FiberPort micropositioners provide an easy-to-use, stable platform for coupling light into and out of FC/PC, FC/APC, or SMA terminated optical fibers. It can be used with single mode, multimode, or PM fibers and can be mounted onto a post, stage, platform, or laser. The built-in aspheric or achromatic lens is available with three different AR coatings and has five degrees of alignment adjustment (3 translational and 2 pitch). The compact size and long-term alignment stability make the FiberPort an ideal solution for fiber coupling, collimation, or incorporation into OEM systems.|
|Triplet Collimators||Thorlabs' High Quality Triplet Fiber Collimation packages use air-spaced triplet lenses that offer superior beam quality performance when compared to aspheric lens collimators. The benefits of the low-aberration triplet design include an M2 term closer to 1 (Gaussian), less divergence, and less wavefront error. |
|Reflective Collimators||Thorlabs' metallic-coated Reflective Collimators are based on a 90° off-axis parabolic mirror. Mirrors, unlike lenses, have a focal length that remains constant over a broad wavelength range. Due to this intrinsic property, a parabolic mirror collimator does not need to be adjusted to accommodate various wavelengths of light, making them ideal for use with polychromatic light. Our reflective collimators are ideal for single-mode fiber.|
|Pigtailed Collimators||Our pigtailed collimators come with one meter of either single mode or multimode fiber, have the fiber and AR-coated aspheric lens rigidly potted inside the stainless steel housing, and are collimated at one of six wavelengths: 532, 830, 1030, 1064, 1310, or 1550 nm. Although it is possible to use the collimator at any wavelength within the coating range, the coupling loss will increase as the wavelength is detuned from the design wavelength. |
|GRIN Fiber Collimators||Thorlabs offers gradient index (GRIN) fiber collimators that are aligned for either 980, 1064, 1310, or 1550 nm and have either FC connectorized, APC connectorized, or unterminated fibers. Our GRIN collimators feature a Ø1.8 mm clear aperture, are AR-coated to ensure low back reflection into the fiber, and are coupled to standard single mode or graded-index multimode fibers.|
|GRIN Lenses||These graded-index (GRIN) lenses are AR coated for applications at 630, 830, 1060, 1300, or 1560 nm that require light to propagate through one fiber, then through a free-space optical system, and finally back into another fiber. They are also useful for coupling light from laser diodes into fibers, coupling the output of a fiber into a detector, or collimating laser light. Our GRIN lenses are designed to be used with our Pigtailed Glass Ferrules and GRIN/Ferrule sleeves.|