Semiconductor laser drive circuit

Abstract

Abstract PURPOSE:To eliminate the temperature effect of current-optical output characteristics by using a laser current control means which detects the intensity of the output light of a semiconductor laser to obtain a prescribed low level and a constant current control means of a laser drive modulating element which obtains a prescribed high level. CONSTITUTION:A photodetector 3 is set in proximity to a semiconductor laser 1 to detect the intensity of the output light. The outputs of monostable multivibrators 14 and 15 which work by the fall and rise of a record pulse P are supplied to sample and/hold circuits 16 and 17 respectively. The outputs of circuits 16 and 17 are supplied to comparators 18 and 19 and compared with the prescribed reference value. The output of the comparator 18 controls a current control transistor TD1 so that the optical output of the laser 1 is kept at a fixed reproduction level when the pulse P is not irradiated. The output of the comparator 19 controls the current of a constant current circuit 20 which is set in series to a switching transistor TR3 for modulation which drives the laser 1 in response to the pulse P. Thus it is possible to eliminate the effect of variation in current- optical output characteristics due to temperatures.

Inventors

• 👤 Masanobu Nishinomiya
• 👤 西宮　正伸
• 👤 Isamu Shibata
• 👤 柴田　勇

Bibliographic Details