AUTOMATIC CONTROLLER FOR OPTICAL OUTPUT

摘要

PURPOSE:To make a system stabilize by providing a means which subtracts the component of (mean value of waveform factor of modulated signal) X (set value of peak power in modulation mode) which is contained in a light quantity detection signal when the optical output is modulated. CONSTITUTION:The modulated signal of a terminal 11 (shown in a figure A) is transmitted through an LPF 30 to average the waveform factor. Thus a signal having a waveform shown in a figure B is obtained. This signal is applied as an input (m) of an analog multiplier 15 and also applied to the output voltage of a power supply 16 for setting of peak power in modulation mode in the form of an input (n). Therefore a waveform (mXn) shown in a figure C is delivered from the multiplier 15 and applied to one of plus inputs of a comparator 13. Thus an output (C+D)-E is obtained from the comparator 13, and the system disturbance due to the waveform C is compensated. If no coincidence is obtained between the output of a light emitting element 1 which is increased by a variable current source 9 and the peak power value set in a modulation mode, (C+D)-E=0 is not satisfied. Therefore the proportion is controlled by an efficiency control circuit 19 between said set value and the value of th source 9. Thus the coincidence is obtained between the set value and the detection output of a photodetector 4.