Which coupler is used when any port can be used as input or output?

Which coupler is used when any port can be used as input or output?

• A. A reflective star coupler
• B. A 1x2 splitter
• C. A 4x4 cross-connect
• D. A 2x2 coupler

Answer: (A)

In optical networks, the ability to use any port as input or output comes from a device where all ports are equivalent and signals can flow bidirectionally through the network without fixed roles. A reflective star coupler achieves this by distributing light from any input port to all other ports and using reflection to enable bidirectional use on the same fiber paths. This means you can inject a signal into any port and it will emerge on the other ports, while signals from those ports can also be received through any port, making the ports interchangeable. A simple 1x2 splitter has a single input and fixed outputs, so the port roles aren’t interchangeable. A 2x2 coupler is a basic two-port device with limited directionality, not designed for universal port use. A 4x4 cross-connect is a switch matrix that routes specific input-to-output paths and isn’t the passive, equal-footing coupler concept described here.

In optical networks, the ability to use any port as input or output comes from a device where all ports are equivalent and signals can flow bidirectionally through the network without fixed roles. A reflective star coupler achieves this by distributing light from any input port to all other ports and using reflection to enable bidirectional use on the same fiber paths. This means you can inject a signal into any port and it will emerge on the other ports, while signals from those ports can also be received through any port, making the ports interchangeable.

A simple 1x2 splitter has a single input and fixed outputs, so the port roles aren’t interchangeable. A 2x2 coupler is a basic two-port device with limited directionality, not designed for universal port use. A 4x4 cross-connect is a switch matrix that routes specific input-to-output paths and isn’t the passive, equal-footing coupler concept described here.