Wavelength division multiplexing communications network supervisory system

摘要

A supervisory system in a wavelength division multiplexing communications network is provided with a first and a second terminal stations and a repeater unit. The first terminal station transmits a supervisory signal to the second terminal station. The second terminal station transfers the supervisory signal to the repeater unit to be monitored. Paths to a hub station A and a hub station B can be a single path by looping back a supervisory signal output from the hub stations A and B for issuing and terminating the supervisory signal at a first and a second branch stations connected through an optical wavelength multiplexing/demultiplexing unit. If the hub station B loops back a supervisory signal, the supervisory signal output from the hub station A can be returned to the hub station A again after circulating the path. If the path of the supervisory signal is set to allow the signal to pass through all repeater units, only one channel is required for a supervisory signal without lowering the modulation rate during a branching operation, and the repeater unit can receive a supervisory signal without fail.