| 摘要 |
PURPOSE:To prevent the waveform of a reception signal deteriorating by setting the duty factor of an optical transmission signal less than 50%, and setting the difference of the phase of the reception signal from an opposite station and that of a crosstalk signal from its own station at the 1/2 of the cycle period of the transmission signal. CONSTITUTION:Directional couplers 3 at both poles are connected with each other with one optical fiber transmission line 4, and a PCM signal whose duty factor is less than 50% is used in optical transmitters at both stations. The difference of the phase of the reception signal from the opposite station at the optical receiver 2 and that of the crosstalk signal from the optical transmitter 1 of its own station is adjusted so as to be set at the 1/2 of the cycle period of the transmission signal with a phase delay adjusting circuit 5. Such phase delay adjustment can be performed, for example, by adjusting the length of an optical fiber. In such a manner, no effect of the crosstalk signal 7 from the optical transmitter 1 is applied on the transmission signal 6 from the opposite station, which prevents the waveform deterioration. |
