| 摘要 |
PURPOSE:To detect abnormality of the photoelectric transducer by synthesizing a transmitting photosignal and a monitoring photosignal which are different in frequency from each other, by inputting the same in the photoelectric transducer and by detecting a corresponding electric signal from the transduced signal. CONSTITUTION:The photosignal from a transmission signal line 1 and the monitoring photosignal 2 having different frequencies from each other are synthesized 3 and transduced 4 photoelectrically. The output thus obtained is separated by filters 5 and 7 into a transmitting electric signal and a monitoring electric signal. The level of the monitoring electric signal is compared 8 with that of a reference electric signal 9 and, when the former is smaller than the latter, the photoelectric transducer 4 is determined to have some abnormality. On the occasion, the monitoring photosignal has a frequency without the frequency band of the transmitting photosignal. By this constitution, the smooth transmission of the signal, as well as the presence of the abnormality in the photoelectric transducer, can be detected and thus the device is effective for practical use. |
