Optical amplifier and optical transmission system including the optical amplifier

摘要

An optical amplifier relates to WDM (wavelength division multiplexing). The optical amplifier includes an optical amplifying unit, an ALC (automatic output level control) circuit for controlling the unit based on the output level thereof, and AGC (automatic gain control) circuit for controlling the unit based on the input and output levels thereof. A selecting circuit alternatively selects and operates the ALC and AGC circuits in accordance with a predetermined rule. Accordingly, the inconvenience occurring in the case of performing only one of ALC and AGC can be eliminated.