Patent ID: 6885825

Claim:
An optical communications apparatus for power balancing a wavelength division multiplexed (WDM) signal output from an add/drop module adding at least one channel to and dropping at least one channel from a signal input thereto, comprising: a gain element optically coupled to the add/drop module and to an add channel port receiving the at least one channel to be added; said gain element imparting optical gain to the at least one channel received from the add channel port; said gain element having a gain profile substantially matching a gain profile of the signal input to the add/drop module; a controller operatively coupled to said gain element, said controller receiving a dropped channel power measurement of the at least one dropped channel dropped from the add/drop module; said controller determining an add path amplification value based on the dropped channel power measurement, a through loss associated with a signal passing through the add/drop module, a drop loss associated with a signal travelling a drop path of the add/drop module; and an add loss associated with a signal travelling an add path of the add/drop module; and said controller controlling said gain element according to the add path amplification value.