| 摘要 |
PURPOSE:To surely receive an information signal even when the light amount of a receiving light beam rapidly and largely changes by generating the delay output signal of a light receiving element output signal and performing signal processing by amplifying the delay output signal with a signal level correction circuit which varies the amplification rate based on the signal level detection result of the output signal. CONSTITUTION:A peak detection circuit 14 detects the level of an output signal S1 of an avalanche photo diode 2 by performing envelope-detection of the distribution output of a directional coupler 12 and outputs the result to an AGC circuit 18. A delay circuit 16 consists of a delay circuit formed by a surface acoustic wave delay element. The remaining distribution output or output signal S1 of the directional coupler 12 is delayed for the prescribed period of time and outputted to the AGC circuit 18. At the AGC circuit 18, the output signal of the delay circuit 16 is amplified by switching an amplification rate according to the signal level detection result. Thus, the signal level of the output signal S2 is corrected to make the signal level of the output signal S2 the prescribed reference level. |
