fiber coupler (FC)
Couplers are electronic components for galvanic isolation and isolation protection of signals. Signal isolation can be achieved optically via optocouplers, but can also be transformer-based, capacitive or magnetic with a magnetic coupler.
In optical fiber technology, couplers are used for splitting or merging optical fibers; they generally operate unidirectionally. The light signal from one optical waveguide is coupled into several other optical waveguides. They are therefore also referred to as 1:X couplers, where X stands for the number of outputs.
Simple couplers for branching or feeding are e.g. fused couplers, bend couplers, face couplers, ground couplers, diffused couplers and biconical taper couplers. Star cou plers are used for splitting or combining a larger number of optical fibers. The coupler has one input and n outputs.
Unidirectional couplers and splitters are used to realize branching within an optical fiber network. The main parameters are: Input signal loss, tap loss and directivity.
In connections with splitters, couplers are called multi-taps. They allow the connection of a larger number of optical fibers and can have 2, 4 or 8 ports. The use of splitters prevents signals sent from one station from reaching the port of another device.
The optical power splits according to the number of outputs, which results in a significant increase in attenuation. The coupler attenuation is calculated from the insertion loss of the coupler plus `10 log(n)`. The insertion loss depends on the number of outputs and is between 2 dB and 5 dB, the total coupler loss is 8 dB (with 4 outputs) and 23 dB (with 64 outputs).