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Fiber Optic Light Trap / Terminators
Fiber Index Matching Block
FC/PC Light Trap
An FTFC1 Terminating
Thorlabs offers two solutions for fiber optic light trapping: the FOBH Fiber Index Matching Block for temporary applications and Light Traps with FC/PC or FC/APC Connectors. The connector-terminated light traps/terminators are also available in kits together with a selection of fixed fiber attenuators. For free-space beam traps and light-blocking devices, please click here.
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Inserting Fiber into the FOBH Index Matching Block / Light Trap
Thorlabs' FOBH Fiber Index Matching Block is a light trap that provides a temporary method for coupling the light out of optical fiber without the use of any connectors or attachments. The vial contains a resilient, dry optical gel that is index matched (n = 1.46) to the core of standard silica optical fiber. While the fiber is pressed against the surface of the gel material, the light is coupled into the gel and is then scattered and absorbed by the black vial. By placing the end of the fiber in firm contact with the surface of the gel, reflections from the end of single mode fiber are reduced to better than 50 dB in most cases.
The FOBH Light Trap is designed for use at visible and infrared wavelengths and has been tested at 635 - 1550 nm. Any type of fiber that has an exposed end face can be used. This includes the use of bare fibers, as well as those that are connectorized with a polished ferrule of any diameter. Glass rods and multimode fibers can also be used, but performance may be reduced. Fiber bundles can also be terminated if all surfaces make good contact.
To use the FOBH Light Trap, hold the fiber or connector and press the end firmly onto the surface of the gel so that it makes good contact. Do not press hard enough to break the gel surface or embed the fiber into the surface. It is important that both the end of the fiber and the surface it touches are perfectly clean, otherwise there will be scattered light that returns up the fiber, reducing the return loss. Improved results may be obtained by cleaning the fiber and light trap surfaces, as well as by avoiding the direct center of the vial and making contact closer to the walls of the vial. The surface of the index-matched gel can be cleaned with alcohol and a soft, lint-free swab.
We also offer Index Matching Gel for reducing signal loss when coupling two fibers together.
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2 x 2 SM Coupler Converted to a 1 x 2 Coupler Using
ADAFC1 FC/PC Mating Coupler and FTFC1 Light Trap
Thorlabs' Terminating Fiber Light Trap Connectors are designed to be used with ports that do not have an output fiber connected to them. Terminating connectors reduce back reflections into the input fiber by up to 50 dB by coupling emitted light into FG025LJA fiber and then diffusing the light within the terminator. In contrast, typical back reflections from an unused port can be as poor as 20 dB. Our terminators are for use with light from 400 - 2100 nm, and have male, FC/PC or FC/APC, 2.0 mm narrow key connectors.
The image on the right shows an FTPC1 fiber optic terminator being used to convert a 2x2 SM fiber coupler into a 1x2 coupler. Here, the FTFC1 is connected to the coupler using an ADAFC1 mating sleeve. Thorlabs offers a range of fiber optic couplers, including 2x2 SM couplers.
Thorlabs' Fiber Optic Attenuator and Terminator Kits each contain six fixed attenuators, five terminators, and a selection of dust caps. Components in the FAK03 kit have FC/PC connectors while those in the FAK05 kit have FC/APC connectors. Each kit is packaged in a plastic box measuring 7.0" x 3.5" x 1.25" (177.8 mm x 88.9 mm x 31.8 mm) and has nine labeled compartments. The label on the lid indicates the contents, associated Thorlabs item number (where applicable), attenuation value and tolerance for the attenuators, and wavelength range and return loss for the terminators. The table to the right lists the description and quantity of each item included in these kits.