Channel identification in communications networks

摘要

Channels in an optical WDM network are each identified by at least two dither tones with which the channel is modulated. A modulating arrangement comprises a plurality of continuous dither tone sources and a selector for selecting at least two dither tones from the plurality in a cyclically repeated sequence. Channel detection by detecting the dither tones makes use of an FFT process which can detect the dither tones for high power channels in a single operation.