| abstract |
(57) [Summary] [PROBLEMS] To reduce the amount of hardware per transmission optical signal speed, and to expect lower cost and smaller system. SOLUTION: An optical demultiplexer 11 demultiplexes the wavelength multiplexed light for each wavelength, and an optical branch 2n splits the demultiplexed light for each wavelength into an optical gate switch 3n and an optical receiver 5n. Receiver 5n The optical signal failure monitoring means 80 is connected via the. When the optical signal fault monitoring means 80 detects the wavelength shift signal OLOW, the signal cutoff signal OLOS, or the S / N ratio decrease signal OSD as the fault detection signal in the optical layer from the light of the wavelength handled by the optical branch 2n, the control means 70 By controlling the optical gate switch 3n to block the passage of the optical signal, the network failure detection signal AIS-O is transmitted downstream. Therefore, when the optical receiver 5n detects no optical signal, the optical signal failure monitoring device 80 sets the AI S can be recognized, and no special hardware is required. |