Create an Account  |   Log In

View All »Matching Part Numbers

Your Shopping Cart is Empty

Bifurcated Fiber Bundles: 2 Fibers

  • High-OH (UV to NIR), Low-OH (Visible to IR), and ZrF4 (UV to MIR) Fiber
  • Seven Fiber Core Sizes from Ø50 µm to Ø1000 µm
  • Custom Fiber Bundles Also Available


Ø105 µm Core Fiber,
High OH

SMA905 Connector

SMA905 Connector

Common Connector Face

BFY400 Shown: Two 400 µm Core Fibers


SMA905 Connector

SMA905 Connectors

FC/PC Connectors (Select Bundles)

Related Items

Please Wait
Fiber Y Bundle Schematic
Click to Enlarge

Bifurcated Fiber Bundle Schematic (Not to Scale)
Typical Applications
  • Channel Broadband Emission from a Sample into Multiple Detectors
  • Fluorescence Microscopy Emission Collection
  • Spectroscopy
  • Illumination
Y Cable Connector Sleeves
Click to Enlarge

The stainless steel sleeve at the end of each leg is engraved with information about the fiber. The example fiber bundle with SMA905 connectors shown here has a mix of high-OH and low-OH legs. We also offer bundles with two high-OH legs, two low-OH legs, or two ZrF4 legs.


  • Y-Cables with One of Four Fiber Configurations
    • High OH (UV Enhanced)
    • Low OH (IR Enhanced)
    • Mixed (One Low OH and One High OH)
    • ZrF4 (UV to MIR)
  • SMA905 or FC/PC 2.0 mm Narrow Key Connectors Terminate All Ends
  • 7 Core Sizes from Ø50 µm to Ø1000 µm
  • Dust Cap for Each Connector Included
  • Custom Versions Available

Thorlabs' Bifurcated Fiber Bundles, also known as fanout or Y-cables, are constructed from two high-grade optical fibers encased in stainless steel tubing for durability. We offer these bundles with seven fiber core sizes from Ø50 µm to Ø1000 µm. As shown in the table below, they are available with two high-OH fibers, two low-OH fibers, one high-OH and one low-OH fiber, or two ZBLAN ZrF4 fibers. ZrF4 fiber bundles are particularly advantageous for spectroscopy, as they offer exceptionally broad transmission from the UV into the mid-IR (285 nm - 4.5 µm). 

All three ends of the cable are terminated with SMA905 or FC/PC connectors. SMA905 connectors are available for each fiber type and diameter. FC/PC connectors are available for high-OH fibers with a 200 or 400 µm core diameter. The stainless steel sleeves of the connectors on the breakout legs of the cable are engraved to indicate the fiber type in each leg. The sleeve of the common connector is engraved with the fiber core size and numerical aperture (NA).

One leg of each bundle contains both fibers before passing through a junction where the cable splits into two legs, each containing a single fiber. Cables with high-OH and/or low-OH fibers are 2 m long from the common end to the split ends, while cables with ZrF4 fibers are 0.5 m long from the common end to the split ends. See the table below for a summary of the dimensions. The two legs are threaded through a sliding clamp so that the breakout length of the cable can be adjusted. The clamp can be locked in place by tightening the 5/64" (2 mm) hex setscrew. A 5/64" (2 mm) hex key is included with each bundle.

When using the common end as the input, these cables perform best when used with sources that provide even illumination across both fiber cores, such as LEDs with a large emitter angle or white light sources like Thorlabs' Stabilized Light Sources. The photos below and to the right illustrate the end face geometry in the common connector.

Each patch cable includes three protective fiber caps that shield the connector ends from dust and other hazards. Bundles with SMA905 connectors include metal CAPSM dust caps;  CAPM Rubber Fiber Caps can be purchased as an alternative option. Bundles with FC/PC connectors include CAPF Plastic Dust Caps.

Custom fiber bundles are available upon request, including straight bundles and bifurcated fiber bundles with one common connector split into two or more connectors. See the Custom Bundles tab for an overview of some of our custom bundle capabilities. Please contact Tech Support for details.

Item # Prefix BFY50 BFY105 BFY200 BFY400 BFY600 BFY1000 BFYZ4 BFYZ6
Fiber Core Size
Ø50 µm Ø105 µm Ø200 µm Ø400 µm Ø600 µm Ø1000 µm Ø450 µm Ø600 µm
Fiber Types
High OH or Low OH High OH, Low OH,
or Mixed
High OH or Low OH High OH or Low OH ZrF4
Wavelength Range 250 - 1200 nm(High OH)
400 - 2400 nm (Low OH)
300 - 1200 nm (High OH)
400 - 2200 nm (Low OH)
285 nm - 4.5 µm
Fiber Attenuation Plot
NAb 0.22 ± 0.02 0.39 ± 0.02 0.20 ± 0.02 @ 2.0 µm
# of Active Fibersc 2
Total Length 2 +0.075 / -0.0 m 0.5 +0.10 / -0.0 m
Common Leg Length 0.10 ± 0.03 m 0.07 +0.02 / -0.00 m
Junction Length 1.63" (41.4 mm) 2.09" (53 mm) 2.36" (60 mm)
Max Breakout Lengthd 1.85 m 0.37 m 0.36 m
Connectors SMA905 SMA905 or FC/PCe SMA905
  • Solarization may occur over time when used below 300 nm. Please click here to view our selection of solarization-resistant bare MM fiber.
  • The NA of the bundle is the same as that of the individual fibers.
  • The common end of our BFY1000 cables has two dark fibers that help align the active fibers during manufacturing
  • Specified with the clamp adjacent to the breakout junction.
  • FC/PC Connectors available for High-OH bundles. Please contact Tech Support for additional options.
Y Cable Common Connector
Click for Details

The common end of a Ø50 µm core Y-bundle. Details of the core, cladding, and epoxy can be seen.

Y Cable Common Connector
Click for Details

The common end of a Ø105 µm core Y-bundle. Details of the core, cladding, and epoxy can be seen.
Fan Out Cable
Click to Enlarge

Custom 1-to-4 Fan-Out Cable

Sample Fiber Bundle Connector Configurations

Custom Fiber Bundles

Thorlabs is pleased to offer custom straight and fan-out fiber bundles with random or mapped fiber configurations. The table below outlines some of our current bundle production capabilities. We are in the process of expanding these production capabilities, so do not hesitate to inquire if you do not see the bundle that you require described here.

Some custom bundles will require techniques outside of our usual production processes. As a result, we cannot guarantee that we will be able to make a bundle configuration to fit the requirements of your specific application. However, our engineers will be happy to work with you to determine if Thorlabs can produce a fiber bundle that fulfills your needs. To receive a quote, please provide a drawing or draft of your bundle configuration.

Fluoride Fiber Bundle
Click to Enlarge

Custom Silica Fiber Bundle with SMA905 Connectors
Custom Bundle Capabilities
Straighta Fan Out (2 or More Legs)a,b
Single Mode Standard (320 to 2100 nm), Ultra-High NA (960 to 1600 nm),