Patent ID: 8131161

Claim:
A DPSK optical receiver comprising: a DPSK demodulation circuit which demodulates a DPSK optical signal and outputs the DPSK demodulated optical signal; an optical bandpass filter which extracts a demodulated optical signal near a center wavelength from the DPSK demodulated optical signal output from said DPSK demodulation circuit; a first photodetector which detects an optical power level of the DPSK demodulated optical signal extracted by said optical bandpass filter; a first control circuit which performs phase control on said DPSK demodulation circuit so as to optimize said DPSK demodulation circuit with respect to the center wavelength of the DPSK optical signal on the basis of the optical power level detected by said first photodetector; an optical coupler which is provided between said DPSK demodulation circuit and said optical bandpass filter, branches part of one of two-system DPSK demodulated optical signals output from said DPSK demodulation circuit, and applies the part of the DPSK demodulated optical signal to said optical bandpass filter; a first delay adjuster which adjusts a delay amount of one DPSK demodulated optical signal output from said DPSK demodulation circuit; and a second delay adjuster which adjusts a delay amount of the other DPSK demodulated optical signal output from said DPSK demodulation circuit.