| 摘要 |
PURPOSE:To achieve a light-receiving circuit which prevents an APD from generating a shot noise when a light signal input is reduced to 'off' state or greatly to an abnormal level for a light-receiving circuit utilizing an avalanche photo diode. CONSTITUTION:In a light-receiving circuit where a gain is controlled by operation of an electrical AGC loop and a light AGC loop and an output of an amplifier is maintained to be constant, when a light signal input is reduced to 'off' state or greatly to an abnormal level, an APD detects generation of noise and applies a control voltage for reducing a bias voltage to the APD. |
