| 摘要 |
PURPOSE:To operate the device always at a point of an optimum value of S/N of a photodetector, by controlling an electric ACG AMP and the photodetector by a current obtained by causing the detection output of a light AGC AMP to pass through a DC/DC converter. CONSTITUTION:A light signal is inputted to an AGC AMP4 through an optical fiber 1, a photoconnector, and a photodetector 3, and a part of the output of the AMP4 is peak detected by a peak detector 5, and a DC/DC converter 8 is controlled by this detection output. Further, the photodetector 3 is controlled by the output of the converter 8, and simultaneously, the AGC AMP4 is controlled through an OP AMP6, and a signal of a constant utput is outputted from the AGC AMP4. The bias of the photodetector is so selected that the gain characteristic of the photodetector for the light input signal has an optimum S/N for the light input signal. |
