| 摘要 |
PURPOSE:To establish the circuit with small sized constitution which can detect the average value of the output of reception system, discriminate the presence of photo signal with the level difference of the average value level, produce alarm without photo signal, and can be usable for the reception system without using the timing signal. CONSTITUTION:The avalanche photo diode 1 receiving photo signal and converting it into an electric signal, amplifying circuit 2 amplifying the electric output converted and the peak detection circuit 3 detecting the peak value of the output of the amplifier 2 are provided. Further, the bias voltage control circuit 4 controlling the bias voltage of the diode 1 with the output of the circuit 3 and the slice circuit slicing the output of the amplifier 2 are provided and the output side of the circuit 5 is provided with the average value detection circuit 6 and the comparison circuit 7. In addition, the average value of the output of the reception system is detected with the circuit 7 and the interruption of photo signal is detected with lower average level than the comparision voltage Vs in specified level, producing the alarm signal. |
