| 摘要 |
PURPOSE:To increase the lifetime of a laser by feeding back the output of the laser to a drive current setting circuit, thereby controlling the drive current and generating the stable laser output. CONSTITUTION:A laser light is monitored, and the bias current of a drive current setting circuit is so controlled that the output value of the monitor falls a value between the upper limit threshold value and the lower limit threshold value. More particularly, the output of partially reflected laser light of the setting circuit 2 is inputted through a monitor detector 9 and an amplifier 10 to the first and second comparators 11, 12, and the upper limit threshold value VH and the lower limit threshold value VL are supplied from a reference voltage generator 13. Thus, the outputs of the comparators 11, 12 control the drive current of a semiconductor laser 1 through an up-down counter 15. |
