Patent ID: 8077384

Claim:
An optical amplifier that is provided in a repeater station of an optical transmission system to amplify a signal light and perform ALC (Automatic Level Control) of output power by means of a variable optical attenuator, wherein: the optical amplifier receives a difference between a target output value and measured output value of an upstream optical amplifier as an expected control volume; the optical amplifier updates a target attenuation value for the variable optical attenuator in accordance with a current target attenuation value set to the variable optical attenuator for ALC, a difference between its own target output value and measured output value, and the expected control volume; the target attenuation value is updated at intervals of time exceeding output convergence time by ALC; and the difference between own target output value and measured output value of the optical amplifier is adopted as an expected control volume for a downstream optical amplifier.