LINE MONITORING METHOD AND DEVICE

摘要

PURPOSE: To detect a fault generation position in a short time with simple constitution. CONSTITUTION: By setting the main line signals of incoming and outgoing optical transmission lines 7a-7(n+ 1) to different wavelengths, the wavelength of loop back signals looped back from respective repeaters 3a-3n and the wavelength of the main line signals transmitted from a transmission terminal station 11 or 21 are prevented from overlapping. Then, by using a branching filter circuit in reception terminal stations 12 and 22, the main line signals and the loop back signals are separated. Also, since the level of the separated loop back signals can be made higher than before, monitoring signals within the loop back signals are detected in a short time.