Apparatus and methods for digital signal constellation transformation

A method of digital signal constellation transformation in an optical communication device, the method comprising:

• receiving an optical signal as an input to a coherent optical receiver;
• generating an analog signal vector representing the optical signal using the coherent optical receiver;
• converting the analog signal vector into a digital signal vector using an analog front-end, wherein the digital signal vector comprises a digital representation of an in-phase (I) component and a quadrature-phase (Q) component of the optical signal;
• generating signal data representing a signal constellation of the digital signal vector using a digital signal processing circuit;
• and
• compensating the signal data for distortion of the signal constellation using an adaptive gain equalizer of the digital signal processing circuit, wherein compensating the signal data for distortion comprises generating an estimate of an angular tilt of the signal constellation and compensating the signal data based on the estimate of the angular tilt.

An integrated optical module comprising:

• a coherent optical receiver configured to receive an optical signal from an optical cable and to generate an analog signal vector representing the optical signal;
• and
• a transceiver configured to process the analog signal vector to generate a digital signal vector comprising a digital representation of an in-phase (I) component and a quadrature-phase (Q) component of the optical signal, wherein the transceiver is further configured to generate signal data representing a signal constellation of the digital signal vector,
• wherein the transceiver comprises an adaptive gain equalizer configured to generate transformed signal data by compensating the signal data for distortion of the signal constellation, wherein the adaptive gain equalizer is configured to generate an estimate of an angular tilt of the signal constellation and to compensate the signal data based on the estimate of the angular tilt.

An integrated optical module comprising:

• a coherent optical receiver configured to receive an optical signal from an optical cable and to generate an analog signal vector representing the optical signal;
• and
• a transceiver configured to process the analog signal vector to generate a digital signal vector comprising a digital representation of an in-phase (I) component and a quadrature-phase (Q) component of the optical signal, wherein the transceiver is further configured to generate signal data representing a signal constellation of the digital signal vector,
• wherein the transceiver comprises an adaptive gain equalizer configured to generate transformed signal data by compensating the signal data for distortion of the signal constellation, wherein the adaptive gain equalizer provides separate distortion compensation for a first portion of the signal data associated with a horizontal polarization of the optical signal and for a second portion of the signal data associated with a vertical polarization of the optical signal.

An optical communication system comprising:

• an optical transmitter configured to provide optical transmissions over an optical network;
• an optical receiver configured to receive an optical signal over the from the optical network and to generate an analog signal vector representing the optical signal;
• and
• a transceiver coupled to the optical transmitter and to the optical receiver, the transceiver comprising:
• an analog front-end configured to convert the analog signal vector into a digital signal vector, wherein the digital signal vector comprises a digital representation of an in-phase (I) component and a quadrature-phase (Q) component of the optical signal;
• and
• a digital signal processing circuit configured to generate signal data representing a signal constellation of the digital signal vector,
• wherein the digital signal processing circuit comprises an adaptive gain equalizer configured to generate transformed signal data by compensating the signal data for distortion of the signal constellation, wherein the adaptive gain equalizer is configured to generate an estimate of an angular tilt of the signal constellation and to compensate the signal data based on the estimate of the angular tilt.