Passive Coupler vs. Active Coupler
Optical couplers can be either passive or active devices. Passive fiber optic couplers require no power for operation. The difference between passive and active couplers is that a passive coupler redistributes the optical signal without optical-to-electrical conversion. Active fiber optic couplers require an external power source. They are electronic devices that split or combine the signal electrically and use fiber optic detectors and sources for input and output. Most fiber optic couplers we’ve seen in optical links are passive devices, such as passive optical splitter and multiplexer (Mux) or de-multiplexer (Demux) in wavelength-division multiplexing (WDM) networks.
Optical Coupler vs Optical Splitter vs Optical Combiner
Optical couplers, optical splitter, and optical combiner are optical devices belonging to fiber optic couplers. Optical splitters are usually Y couplers, T couplers, or tree couplers that have only one input port and two or more output ports. On the contrary, optical combiners have only one output port and two or more input ports. So you can also see the numeral “1” in the descriptions of optic splitters and combiners, like 1×2 fiber optic splitters/combiners, 1×4 splitter/combiners, and 1 x 64 splitters. However, for optical couplers, they can be in any form we have mentioned above, such as star couplers, 2×2 couplers, 1×4 couplers, tree couplers, etc. Each device is designed for its purpose.