Digital coherent receiving apparatus

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 phase detector includes:
• a plurality of equalizing filters configured to process respectively that equalizes the digital signal by using different equalizing characteristics,
• a plurality of detecting unit configured to detect a plurality of the candidate phases of the digital signal processed by each of the equalizing filters, and
• a selector configured to select one of the detected candidate phases as the detected phase.

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 phase detector includes:
• a plurality of equalizing filters configured to process respectively that equalizes the digital signal by using different equalizing characteristics,
• a plurality of detecting units configured to detect a plurality of the candidate phases of the digital signal processed by each of the equalizing filters,
• a convertor configured to variously converting the plurality of the candidate phases, and
• a phase generator configured to generate the phase by combining the plurality of the candidate phases using a diversity combining method and configured to output the phase.