Abstract: There is provided a shutdown controller that monitors the temperature of an optical multiplexer and maximizes the loss of an optical attenuator when a temperature monitor result is abnormal. An optical level change detection circuit section is disposed with respect to an optical level monitor of individual monitors in an optical add/drop multiplexer. An optical level monitor of a total main signal is disposed downstream of the optical multiplexer. The inconsistency of the wavelength number is detected by comparing the total of the optical level monitors of the individual channels with the optical level value of the optical level monitor, upon which shutdown control is performed in which the loss of the optical attenuator is maximized in only the channel whose optical level change is detected by the optical level change detection circuit section.

Abstract: An output light intensity monitor unit of an optical repeater monitors an output light of an output point of the optical repeater. A reflected light intensity monitor unit monitors a reflected light returning from an optical fiber to the output point, An optical fiber transmission line loss from the apparatus output point to an optical fiber open end and a light intensity emitted from the open end are estimated from a monitored reflected light intensity, and a reflection abnormality detection threshold for detecting the reflection abnormality if the light intensity emitted from the open end exceeds a reference light intensity is prescribed. An output light intensity lowering amount and a reflection abnormality recovery threshold are prescribed from an output light intensity monitored at the apparatus output point and the reflected light intensity so that an open end output light intensity may be lowered to the reference light intensity.

Abstract: Disclosed herein are a device and a method for an optical signal changeover that will not necessitate any addition to the capacity of the optical signal selection unit even when the N×M optical switches are expanded in scale, but can keep the optical signal selection unit compact in size and enhance the reliability of the unit. The optical signals received from plural optical transmission lines are converted into predetermined wavelengths by the wavelength conversion unit based on the settings given from the system monitoring control unit. The converted optical signals are bifurcated by the optical bifurcating unit and inputted to the optical switches of the active system and the optical switches of the stand-by system.

Abstract: There is provided a shutdown controller that monitors the temperature of an optical multiplexer and maximizes the loss of an optical attenuator when a temperature monitor result is abnormal. An optical level change detection circuit section is disposed with respect to an optical level monitor of individual monitors in an optical add/drop multiplexer. An optical level monitor of a total main signal is disposed downstream of the optical multiplexer. The inconsistency of the wavelength number is detected by comparing the total of the optical level monitors of the individual channels with the optical level value of the optical level monitor, upon which shutdown control is performed in which the loss of the optical attenuator is maximized in only the channel whose optical level change is detected by the optical level change detection circuit section.

Abstract: Disclosed herein are a device and a method for an optical signal changeover that will not necessitate any addition to the capacity of the optical signal selection unit even when the N×M optical switches are expanded in scale, but can keep the optical signal selection unit compact in size and enhance the reliability of the unit. The optical signals received from plural optical transmission lines are converted into predetermined wavelengths by the wavelength conversion unit based on the settings given from the system monitoring control unit. The converted optical signals are bifurcated by the optical bifurcating unit and inputted to the optical switches of the active system and the optical switches of the stand-by system.