Patent ID: 8098988

Claim:
An optical add/drop multiplexing device for demultiplexing a first multiplexed optical signal input via a first optical cable into a plurality of optical signals according to wavelengths, dropping one or more of the demultiplexed optical signals to a transponder, adding one or more optical signals output from the transponder to the demultiplexed optical signals, multiplexing the demultiplexed optical signals into a second multiplexed optical signal, and outputting the second multiplexed optical signal to a second optical cable, the optical add/drop multiplexing device comprising: an injecting unit configured to inject one of measurement optical signals, each of whose wavelengths corresponds to a wavelength of a different one of the demultiplexed optical signals, into a core of a multicore cable within the optical add/drop multiplexing device, the core being used to transmit one of the demultiplexed optical signals which has the same wavelength as the one of the measurement optical signals; a preventing unit configured to prevent the one of the measurement optical signals from emanating toward the second optical cable; a measuring unit configured to measure optical levels of the one of the measurement optical signals at positions before and after the corresponding core of the multiple cable; a calculating unit configured to calculate, for the wavelength of the one of the measurement optical signals, optical loss of the corresponding core of the multicore cable, based on the measured optical levels; and an informing unit configured to report the calculated optical loss.