OPTICAL WAVE DETECTION RECEIVER

摘要

PURPOSE:To increase the control range of an automatic gain control circuit by controlling the locally oscillated light which is supplied to a photodetector so that the output signal of a reception amplifying circuit is set at a prescribed level. CONSTITUTION:The signal light 1 is multiplexed with the locally oscillated light 5 sent from a local oscillation light source 3 by an optical multiplexer 2 and supplied to a photodetector 7. The detector 7 gives the optical heterodyne wave detection to the input light and converts it into an ASK signal of an intermediate frequency. This ASK signal is supplied to a reception amplifying circuit 8. The binary pulse signal output of the circuit 8 is supplied to a processing circuit 9 as well as to a peak value detecting circuit 11. The circuit 11 detects the peak value of a pulse signal. A comparator 12 compares the detected peak value with the reference value and then controls the amplification factor of the circuit 8 so that the detected peak value is set at a fixed level. Thus the degree of attenuation is controlled for an optical controller 4 which controls the level of the light 5.