A passive component is designed to route light energy from an input port to one or several output ports while losing as little energy as possible. The component must be stable and insensitive to environmental stress as well as insensitive to the state of polarization.
Passive components are used in many different applications throughout optical networks and subsystems. Connectors, couplers, isolators, circulators, filters, multiplexers, and demultiplexers of all kinds form part of the optical layer; they help ensure that information-encoded light energy arrives at the right place in the network under the right conditions.

 

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