FAULT BLOCK IDENTIFYING DEVICE FOR OPTICAL REPEATER TRANSMISSION SYSTEM

摘要

PURPOSE:To use a main signal-to-noise power rate measuring instrument with a small dynamic range by providing means to generate optical noise with the same character as optical noise generated at a repeater and to transmit it to a transmission line while being coupled with signal beams. CONSTITUTION:A transmitter 20a superimposes the optical noise outputted from an optical noise generator 23 and the signal beam outputted from a transmission circuit 21 and transmits them to the transmission line. The transmitted optical signal superimposed with the optical noise is returned at a repeater 102, turned to received signal beams and inputted to a main signal-to-noise power rate (S/N) measuring instrument or error rate measuring instrument 31 of a receiver 30, and an S/N or an error rate is measured. The S/N detected at the S/N measuring instrument 31 of the receiver 30 is degraded by the optical noise generated at respective optical amplifiers 11 and 12 of repeaters 101 and 102 in addition to the optical noise superimposed by the transmitter 20a. However, the difference of the S/N caused by the position of the returning repeater is reduced. Therefore, the dynamic range of the S/N measuring instrument 31 can be reduced.