| 摘要 |
PURPOSE:To prevent cross modulation between channels due to the nonlinear distortion of a light emitting element without increasing required number of optical fibers by separating a frequency division multiplex signal into a residual side band amplitude modulation video signal, demodulating it to obtain the original plural video signals and sending them. CONSTITUTION:An optical transmission line 3 consists of optical fibers and sends the light from a light emitting element L1 to a photodetecting element L2 of a photodetector 2. The photodetector 2 uses the photodetecting element L2 being a photodiode or an avalanche photodiode to convert an optical signal sent through the line 3 into an electric signal, which is maplified by an amplifier AMP 2, fed to a demodulation circuit DEM through a band pass filter BPF 00 to obtain a frequency division multiplex signal. Then, the frequency division multiplex signal is fed to a low pass filter LPF 2 to obtain a base band video signal component Vo1, which is amplified by an amplifier AMPV1 to obtain the original video signal Vi1. Thus, the cross modulation due to the nonlinearity of an electrooptic conversion element is prevented and multi-channel signals are sent through a few optical fibers. |
