Apparatus for optical path monitoring and an optical shutter for preventing signal transmission in a faulty optical path

摘要

A node for a wavelength division multiplexing communication system having first and second communication paths along which information-bearing radiation propagates in opposite directions. The node includes an add/drop multiplexer; an optical shutter for monitoring a power of the information-bearing radiation propagating along the first path and for generating a corresponding radiation power indicative signal; a control unit for comparing the indicative signal with a threshold value to generate a control signal; and a shutter switch for selectively substantially transmitting or blocking the radiation propagating along the second path in response to the control signal.