| 摘要 |
PURPOSE: To improve the reliability of the transmission of a signal by easily performing the multiplexing of a main signal and a maintenance signal. CONSTITUTION: In a remote station 40, an intensity modulation is directly performed for outputted light by the main signal converted into the code which does not contain DC components in an electric/optic conversion part 42, a polarization plane modulation is performed for the light by the maintenance signal of a low frequency area from the power spectrum of the modulation frequency of the main signal in an optical polarization plane modulation part 43, and the light is transmitted as signal light to an optical transmission line 50. In a main station 60, the fetched signal light is branched in an optical coupler 61, one signal light is directly converted into the electric signal according to the intensity of light in an optic/electric conversion part 62, the main signal is outputted, the other signal light is converted into the signal light of optical intensity modulation components in an analyzer 64, the signal light is directly converted into the electric signal according to the intensity of light in an optic/ electric conversion part 65, and a maintenance signal is outputted. |
