Patent ID: 7333262

Claim:
An optical amplifying method of an optical amplifier connected to an optical transmission line, the method comprising the steps of: detecting an optical input and output power of said optical amplifier; obtaining a difference between a target gain and a measured gain of said optical amplifier obtained based on the detected optical input and output power to produce an error signal; applying said error signal to each of a proportional calculation and an integral calculation to create respective proportional and integral control signals, and adding proportional and integral control signals to create a drive current of at least one pump laser diode provided in said optical amplifier; controlling the gain of said optical amplifier with the drive current; and adjusting a control parameter of the proportional calculator in response to the detected optical input power, said control parameter being a proportional constant by which said error signal is multiplied to form said proportional control signal, said proportional constant being represented by a function of the optical input power as a result of the adjusting the control parameter in response to the detected optical input power.