Patent ID: 8649689

Claim:
A digital coherent receiving apparatus, comprising: a receiver configured to receive a light signal; a first oscillator configured to output a local light signal; a hybrid unit configured to mix the local light signal output from the first oscillator with the light signal received by the receiver; a second oscillator configured to output a sampling signal of a sampling frequency, the second oscillator changing the sampling frequency in response to an input control signal; a converter configured to convert the mixed light signal into digital signal by sampling the mixed light signal with the sampling signal; a waveform adjuster configured to adjust a waveform distortion of the digital signal converted by the convertor; a phase adjustor configured to adjust a phase of the digital signal adjusted by the waveform adjustor; a demodulator configured to demodulate the digital signal adjusted by the phase adjuster; a phase detector configured to detect a phase of the digital signal adjusted by the phase adjuster; and a control signal output unit configured to output a control signal on the basis of the detected phase signal to the second oscillator, wherein the control signal output unit includes: a noise canceller configured to cancel noise in the phase detected by the phase detector, and a generator configured to generate the control signal in reference to the phase after cancelling the noise by the noise canceller and configured to output the control signal to the second oscillator, wherein the phase adjustor adjusts the phase of the digital signal on the basis of the phase after cancelling the noise by the phase detector.