| 摘要 |
PURPOSE:To prevent hindrance to the evaluation of circuit quality by inhibiting the signal break detecting function of an optical receiver from operating even an insertion signal is added. CONSTITUTION:A light input signal is converted by an APD photodetector 1 into an electric signal, which is amplified by an amplifier 2 and then amplitudeequalized by an equalizer 3; and a digital signal is regenerated by a discriminating circuit 4 and 1ed out as a reception output through a gate 5. When the level of the light signal input decreases, an AGC circuit 6 operates to increase the multiplication factor of the photodetector 1 and the gain of the amplifier 2, but the output of a timing regenerating circuit 7 decreases below a certain value and then a signal break detecting circuit 8 generates an output to close a gate 5 through a gate 9, stopping the reception output. When a signal X of specific frequency is added to a main signal, an X detecting circuit 10 generates an output to close the gate 9, so the reception output is not stopped by the output of the signal break detecting circuit 8. |
