Features

• Operating Wavelength Ranges: 1310 ± 70 nm and
  850 ± 40 nm
• Flat Spectral Response
• Low Insertion Loss
• Available Coupling Ratios: 1:99, 10:90, and 50:50
• FC/APC Connectors
• Customized Fiber Lead Lengths and Connectors Available

Fiber Optic Couplers
Fiber optic couplers are devices with one or more input and output fibers. The FC850-40 and FC1310-70 series of couplers have 2 input and 2 output fibers as shown in the photo to the right. Light input into the device from a single fiber on one end is coupled, at a fixed ratio, into the other set of leads.

For example, light input into lead A1 of the FC850-40-01-APC coupler will be split so that 99% of the transmitted light is coupled into the B2 lead while the other 1% is coupled into the B1 lead. The coupler is bidirectional, in that you can input the light into any of the fiber leads and have the transmitted light split between the two leads in the other lead pair.

A broadband light source is spectrally analyzed, and the trace is saved as Reference 'A'. Next, this reference light is sent to the coupler; the output of the coupler is analyzed and saved as trace 'B' (Figure 1). These two traces are shifted so that their peak value is 0 dB in order that they share a common reference intensity (Figure 2). The difference ('A-B') between these two traces is calculated as a function of wavelength and plotted in Figure 3. The result is the spectral uniformity curve for the fiber coupler, showing the variation in transmitted intensity as of function of wavelength for the specified operating range of the fiber coupler.

Figure 1

Figure 2

Figure 3

Each possible optical path is analyzed, yielding 4 traces for each coupler as shown in the sample plot below. Every OCT fiber coupler placed is inventory is tested to ensure that it meets the criteria listed below.

FC850-70-xx-APC

• Region Analyzed: 850 ± 40 nm
• Maximum Variation from 0 dB: 2.0 dB
• Region Analyzed: 850 ± 20 nm
• Maximum Variation from 0 dB: 1.3 dB

Figure does not represent a specific coupling ratio, for demonstrational purposes only.

We are using the 10202A 2x2 Coupler in the examples below and we are focusing on the insertion loss specification. The wavelength of Signal A is 1550 nm and the wavelength of Signal B is 1540 nm. Please refer to the picture above for port numbers and signal paths, expected output is summerized in the table below for various set up schema.

One Port Signal Tapping

Two Port Signal Mixing

Coupling a Return Signal with a Reflector on Port 3