Patent ID: 7865079

Claim:
A drift feedback compensator for compensating drift comprising: an optical switch comprising a plurality of input ports, an output port, and a switch control, wherein an insertion loss between at least one of the input ports and the output port is controllable in response to a control signal applied to the switch control; a variable optical attenuator having a VOA input port optically coupled the output port of the optical switch, a VOA output port and a VOA control, wherein an attenuation between the VOA input port and VOA output port is settable in response to an attenuation setting signal applied to the VOA control; an optical splitter optically coupled to the VOA output port for splitting an optical output signal from the VOA output port into a tapped signal and a through signal; an optical channel monitor optically coupled to the optical splitter for receiving the tapped signal and providing a feedback signal; and a controller for applying the control signal to the switch control and the attenuation setting signal to the VOA control in response to the feedback signal received from the optical channel monitor; wherein the control signal modulates the insertion loss to produce an insertion loss modulation at a dither frequency, wherein the attenuation setting signal modulates the attenuation to produce an attenuation modulation at the dither frequency, and wherein the insertion loss modulation is anti-phase to the attenuation modulation.