Patent ID: 6895183

Claim:
A system for detecting, in an optical layer, faults of an optical network, said system comprising: an optical wavelength division multiplex coupler comprising an arrayed waveguide diffraction grating to serve as: a wavelength multiplexer that receives a plurality of mutually-different-wavelength light signals on plural paths and provides a wavelength-multiplexed light signal as an output optical signal; and a wavelength divider that receives a sampling of said output wavelength-multiplexed light signal and divides said sampling of wavelength-multiplexed light signal into a plurality of wavelength-light signals on plural paths that correspond in wavelength to and that travel in a direction reverse to said plurality of mutually-different-wavelength light signals on plural paths; and a monitor that monitors one or more of said wavelength-light signals to detect failures in said optical network signal in an optical layer.