Patent ID: 7400444

Claim:
An optical amplifier receiving and amplifying an input optical signal and producing an output optical signal, comprising: a power detecting unit that detects at least one of an input power of the input optical signal and an output power of the output optical signal and produces a corresponding power detection output; a temperature detecting unit that detects an operating temperature of an erbium-doped fiber (EDF), a change in the operating temperature causing the gain of the optical amplifier to change, and produces a corresponding temperature detection output; and a control unit that calculates a power of an amplified spontaneous emission (ASE) based on the power and temperature detection outputs, and adds a power factor that is determined by the power of the ASE to the input power, to maintain the gain of the optical amplifier at a predetermined value; the control unit controls the gain to be gain = Pout Pin + Poutase Gset ⁢ ( Pin , T ) where Pin represents the input power, Pout represents the output power, Gset represents a set gain, Poutase represents the power of the ASE, and T represents the operating temperature of the EDF.