A bidirectional optical transmission system having a light-interruption detecting function.

摘要

Disclosed is a bidirectional optical transmission system for effecting bidirectional optical transmission between offices by utilizing a common optical transmission line (30). Each office (10;20) comprises: a light transmitting unit (160;260) for transmitting a light signal to another office (20;10); a light receiving unit (170;270) for receiving a signal from the other office (20;10); and a light passing unit (130; 230) for passing the transmission signal from the light transmitting unit (160; 260) to the optical transmission line (30) and for passing the receiving signal from the optical transmission line (30) to the light receiving unit (170;270). To discriminate whether the received signal is the signal from the other office (20;10) or from the same office (10; 20) by crosstalk through the light passing unit (130;230), the light transmitting unit (160; 260) comprises a light-interruption detecting signal superimposing unit (162;262) for superimposing a light-interruption detecting signal on the transmission signal, the frequencies of the light-interruption detecting signals from the first office (10; 20) and from the other office (20;10) being different from each other; and the light receiving unit (170; 270) comprises a light-interruption detecting signal detecting unit (172;272) for detecting the light-interruption detecting signal from the other office (20;10) by identifying the frequency of the light-interruption detecting signal from the other office (20;10).