OPTICAL SIGNAL RELAY DEVICE, OPTICAL COMMUNICATION SYSTEM AND COMMUNICATION CONTROL METHOD

PROBLEM TO BE SOLVED: To provide an optical signal relay device performing gain adjustment of an optical amplifier by monitoring the intensity of output light, in which excessive output of optical signal can be prevented by detecting problems in the monitoring of the output light exactly, and to provide an optical communication system and a communication control method.SOLUTION: An optical signal relay device for transmitting a received optical signal while amplifying includes a semiconductor optical amplifier for receiving and amplifying the optical signal, a light-receiving element outputting a current of a magnitude corresponding to the intensity of the output light from the semiconductor optical amplifier, and a control section for stopping or limiting amplification of the semiconductor optical amplifier when the output current from the light-receiving element goes below a threshold, which is smaller by a predetermined value than the output current from the light-receiving element at the time when the semiconductor optical amplifier is not receiving the optical signal. 【課題】出力光の強度をモニタして光増幅器の利得調整を行なう光信号中継装置において、出力光のモニタにおける不具合を的確に検知し、光信号の過出力を防ぐことが可能な光信号中継装置、光通信システムおよび通信制御方法を提供する。【解決手段】受信した光信号を増幅して送信する光信号中継装置であって、前記光信号を受けて増幅する半導体光増幅器と、前記半導体光増幅器の出力光の強度に応じた大きさの電流を出力する受光素子と、前記半導体光増幅器が前記光信号を受けていないときの前記受光素子の出力電流より所定値小さい閾値と比べて、前記受光素子の出力電流が小さくなった場合に、前記半導体光増幅器の増幅を停止または制限する制御部とを備える。【選択図】図３