OPTICAL COMMUNICATION METHOD

PROBLEM TO BE SOLVED: To enhance a reception sensitivity and also to eliminate phase noise by detecting signal light modulated in a polarization plane, executing a square processing in a detection signal and taking-out a low frequency component. SOLUTION: The mixed light of signal light with station emittment light is received by a light receiving equipment 10 so as to obtain the signal adding phase noise. The phase signal is taken-out by BPF 11 and multiplied by itself in a square equipment 12 so that the signal adding phase noise in a central frequency 4GHz and the signal not adding phase noise in 500MHz are obtained. In the signals, only the low frequency component is taken-out by LPF 13. Thus, signal regeneration is made possible.