Optical amplifier having an attenuator for attenuating input power to eliminate a surge in an amplified optical signal

摘要

An optical amplifier prevents generation of an optical surge when an input signal to the optical amplifier is interrupted. A synthesized signal of an input signal light (Pi) and a pumping light is input to an optical amplifying medium (EDF). An input signal light interruption detecting circuit (BS1, PD1, COMP) detects an interruption of the input signal light (PI). A variable attenuator element (ATT) is provided on a signal light input side of the optical amplifying medium (EDF) so as to attenuate the input signal light (Pi). The variable attenuator element (ATT) is controlled based on an output of the input signal light interruption detecting circuit so that a degree of attenuation of the variable attenuator element (ATT) is increased when the input signal light (Pi) is interrupted and the degree of attenuation is gradually decreased when the input signal light (Pi) returns.