What type of coupler allows any port to be used as an input or output in a network?

What type of coupler allows any port to be used as an input or output in a network?

• A. A reflective star coupler
• B. A passive 4x4 splitter
• C. An optical circulator
• D. A WDM coupler

Answer: (A)

The key idea is bidirectional, port-agnostic connectivity. A reflective star coupler is a multiport device that distributes light from any input port to all other ports, and, crucially, it reflects signals back into the network so any port can serve as either an input or an output. This symmetry means there’s no fixed role for each port—any port can inject or receive signals, enabling flexible, all-port input/output operation. In contrast, a passive 4x4 splitter has fixed behavior and typically requires designated input ports; it splits signals but doesn’t inherently allow every port to act as both input and output. An optical circulator is directional, routing light in one preferred path from one port to another, so not all ports can be used interchangeably. A WDM coupler handles different wavelengths rather than enabling port-level bidirectionality, so it doesn’t provide the same input/output flexibility.

The key idea is bidirectional, port-agnostic connectivity. A reflective star coupler is a multiport device that distributes light from any input port to all other ports, and, crucially, it reflects signals back into the network so any port can serve as either an input or an output. This symmetry means there’s no fixed role for each port—any port can inject or receive signals, enabling flexible, all-port input/output operation.

In contrast, a passive 4x4 splitter has fixed behavior and typically requires designated input ports; it splits signals but doesn’t inherently allow every port to act as both input and output. An optical circulator is directional, routing light in one preferred path from one port to another, so not all ports can be used interchangeably. A WDM coupler handles different wavelengths rather than enabling port-level bidirectionality, so it doesn’t provide the same input/output flexibility.