Patent ID: 8908264

Claim:
A controller for reducing a transient variation of gain of an optical amplifier, which includes an optical tap having an input port and first and second output ports, for receiving an input optical signal at the input port, splitting the input optical signal into first and second optical signals, and directing the first and the second optical signals to the first and the second output ports, respectively; a photodetector coupled to the first output port, for detecting the first optical signal; a length of an active optical fiber between first and second ends thereof, wherein the first end is coupled to the second output port, for amplifying the second optical signal when the active optical fiber is pumped by an optical pump source; and a variable optical attenuator coupled to the second end of the active optical fiber, for attenuating the amplified second optical signal in dependence upon a control signal applied to the variable optical attenuator, so as to produce an output optical signal, wherein the controller is capable of being coupled to the photodetector and to the variable optical attenuator, wherein the controller comprises a control circuit adapted to generate, based on the detected first optical signal, the control signal for the variable optical attenuator, having a magnitude and a temporal profile corresponding to a magnitude and a temporal profile of a transient change of optical gain of the active optical fiber caused by a transient change of optical power of the second optical signal, thereby reducing the transient variation of gain of the optical amplifier.