Patent ID: 8873973

Claim:
A digital coherent receiver comprising: a digital converter to sample a signal received from an optical transmission path and generate a digital signal; a sampling phase detector to detect a phase of the sampled digital signal; a phase adjustor to adjust a sampling phase of the digital signal based upon the detected phase; and a demodulator to demodulate the phase-adjusted digital signal, wherein the phase detector includes two or more filters to equalize the digital signal with different equalization characteristics; two or more sensitivity monitoring phase detectors, each connected to one of the filters and configured to output a phase detection signal representing a phase of an output signal from the associated filter and a sensitivity monitoring signal representing a sensitivity of the phase detection, two or more sensitivity correction coefficient generators, each generating a sensitivity correction coefficient for correcting the associated phase detection signal using a square sum of the sensitivity monitoring signals, and an adder to add the phase detection signals that have been corrected by the sensitivity correction coefficients and output a phase signal.