| 摘要 |
PURPOSE:To stepwise detect the deterioration state of a semiconductor laser element in a semiconductor laser transmitter. CONSTITUTION:A semiconductor laser driving circuit 1 supplies a driving current modulated corresponding to an input signal from an outside to a semiconductor laser LD and a photodiode PD receives one part of the output optical signal of the semiconductor laser LD, and outputs a monitor signal. An automatic output control circuit 2 supplies a bias current to the semiconductor laser driving circuit 1 so that the level of the output optical signal of the semiconductor laser LD can be constant, based on the monitor signal. A current/voltage conversion circuit 3 monitors the current amount of the bias current supplied from the automatic output control circuit 2 to the semiconductor laser driving circuit 1, and outputs a voltage signal corresponding to it. An analog/digital conversion circuit 4 stepwise outputs an alarm signal according to preliminarily set plural threshold values, from the voltage signal supplied from the current/voltage conversion circuit 3. |
