BASE BAND IM OPTICAL PICTURE TRANSMITTER

摘要

PURPOSE:To decrease the increase in distortion of an optical output due to temperature or secular change by detecting a peak value of synchronism tip of the optical output and using this value so as to control a bias current of a laser diode thereby stabilizing an optical output. CONSTITUTION:A video input signal is subject to peak clamp by a signal current drive circuit 1 and its output is added with an output of a bias current circuit 2 to drive a laser diode LD3 and an optical output is transmitted. A photo diode PD4 monitors an optical output, detects (5) a peak value of the optical output and a bias current is controlled by a comparison amplifier circuit 9 so as to apply optical output stabilization corresponding to the change in the threshold value. On the other hand, a pilot signal is extracted from an output of the PD4 by a BPF6, the peak value is detected (7), the clamp level of a signal current circuit is controlled by an output of a comparison amplifier circuit 8 so as to stabilize the optical output against the ambient temperature change of the differentiation efficiency of the LD3 and secular change.