| 摘要 |
PURPOSE:To improve the maximum allowable photoreception power by amplifying the output signal of an avalanche photodiode while controlling the gain of the amplifier so as to make the signal level constant. CONSTITUTION:The optical current of the avalanche photodiode(APD) 10 is C increased as the optical input becomes larger, a voltage drop in a correction resistance circuit 12 is increased, an APD bias voltage is decreased to control the current multiple characteristic to an optimum value. When the optical input is increased to a value or over, the voltage drop in the correction resistance circuit 12 is too large, the current multiple factor is lowered and the frequency characteristic of the APD is deteriorated. In such a case, the voltage drop of the correction resistance circuit 12 is limited by a prescribed value by the voltage limit circuit 13 and the current multiple factor is fixed to s prescribed value. Thus, the maximum allowable photodetection power of the optical receiver is improved. |
