Patent ID: 7542678

Claim:
A method for providing a supervisory channel in a multi-node wavelength division multiplexing (WDM) fiber-optic communication system, comprising: at an upstream node, demultiplexing a WDM optical signal; and modulating an attenuation level of at least one demultiplexed WDM channel of the WDM optical signal passing through the upstream node to impart thereby supervisory information to the optical signal; wherein said supervisory information is adapted for use by a downstream node of the system, and the attenuation level is controlled in a manner facilitating equalization of an optical power between demultiplexed WDM channels of the optical signal; said upstream node includes an Optical Add-Drop Multiplexer (OADM) having at least one variable optical attenuator disposed in at least one respective optical path supporting said WDM channels of the optical signal passing therethrough; and said variable optical attenuator is controlled using a sum of a modulating signal of the supervisory channel and a setting for a power equalizing attenuation between the demultiplexed WDM channels.