| 摘要 |
PURPOSE:To eliminate frequency fluctuation and to realize high reception sensitivity by sending a pilot signal apart from a center frequency of a signal light by a prescribed frequency interval while being subjected to wavelength multiplex with the signal light. CONSTITUTION:The 1st data signal 46 is amplified by an optical phase modulator drive circuit 5, fed to an optical phase modulator 2, subjected to binary PSK modulation and becomes the 1st signal light 7. The 1st signal light 7 and pilot signal light 8 having the same frequency fluctuation are subjected to multiplex by the 1st synthesizer 4 and sent through a single mode fiber 44. On the other hand, an optical reception section 43 uses a photodetector 17 to apply optical heterodyne detection to the synthesized light 16 and the output of the photodetector 17 includes the 1st beat signal 31 comprising the pilot signal light 8 and the local oscillation light 14 and the 2nd beat signal 32 comprising the signal light 7 and the local oscillation light 14. The same frequency fluctuation component of the two beat signals is cancelled by making them equal in phase by using a phase adjusting circuit 45, the the 2nd intermediate frequency signal 23 has a spectrum without frequency fluctuation. |
