| 摘要 |
In an optical receiver circuit (100) in which an optical input signal is amplified by an optical amplifier (1) and converted to or electrical signal by optical detector (2), and the amplified optical signal is amplified by an equalization amplifier (4) so as to obtain an optical received signal, an output peak level of the equalization amplifier (4) is detected by a peak detection circuit (7), an error difference of the peak level is amplified by an error amplification circuit (9), and a gain of the optical fiber amplifier (1) is controlled by a gain control circuit (10), thereby fixing a level of the received signal. In the above-mentioned structure, an input signal loss detection circuit (8) detects an input signal loss from an output of the peak detection circuit (7), and the gain of the optical fiber amplifier (1) is controlled by the gain control circuit (10) to be sufficiently lower than the maximum gain at the time of the detection. Thereby, even in a case where a level of the optical input signal abruptly increases from the input signal loss, damage of an optical detector and saturation of a receiving electric circuit can be prevented, so that the circuit can be operated again. |
