Optical Coherent Receiver Optimization

A coherent optical receiver comprising:

• an optical front end that receives an optical signal including a carrier signal modulated by a data signal, and converts the received optical signal to an electrical signal corresponding to the data signal;
• and
• a digital modem coupled with the optical front end, the digital modem including
• an analog-to-digital converter that converts the electrical signal to digital data,
• a carrier phase estimator that estimates the phase of the optical signal by averaging the digital data with an adjustable number of taps of the carrier phase estimator,
• a forward error correction estimator that determines error statistics based on the averaged digital data, and
• a controller that automatically adjusts the number of taps in the carrier phase estimator in response to the error statistics determined by the forward error correction estimator.

A method for setting adaptive equalizer gain in a coherent optical receiver comprising:

• receiving an optical signal at a coherent optical receiver;
• mixing, by an optical hybrid mixer of the coherent optical receiver, the received optical signal with a local oscillator signal to generate a mixed optical signal;
• converting, by a photodetector of the coherent optical receiver, the mixed optical signal to an electrical signal;
• converting, by an analog-to-digital converter of a digital modem associated with the coherent optical receiver, the electrical signal to digital data;
• equalizing the digital data by an adaptive equalizer of the digital modem, the adaptive equalizer having an adjustable gain;
• determining, by a forward error correction estimator of the digital modem, receiver performance statistics based on the equalized digital data;
• and
• automatically adjusting, by a controller of the digital modem, the gain in the adaptive equalizer in response to the determined receiver performance statistics.

A coherent optical receiver comprising:

• an optical front end that receives an optical signal including a carrier signal modulated by a data signal, and converts the received optical signal to an electrical signal corresponding to the data signal;
• and
• a digital modem coupled with the optical front end, the digital modem including
• an analog-to-digital converter that converts the electrical signal to digital data,
• an adaptive equalizer having an adjustable gain, such that the adaptive equalizer equalizes the digital data,
• a forward error correction estimator that determines error statistics based on the equalized digital data, and
• a controller that automatically adjusts the gain of the adaptive equalizer in response to the error statistics determined by the forward error correction estimator.

A method for controlling local oscillator frequency in a coherent optical receiver comprising:

• receiving an optical signal at a coherent optical receiver;
• mixing, by an optical hybrid mixer of the coherent optical receiver, the received optical signal with a local oscillator signal to generate a mixed optical signal, where the local oscillator signal is generated by a tunable laser of the optical hybrid mixer;
• converting, by a photodetector of the coherent optical receiver, the mixed optical signal to an electrical signal;
• converting, by an analog-to-digital converter of a digital modem associated with the coherent optical receiver, the electrical signal to digital data;
• processing, by a frequency offset estimator of the digital modem, the digital data to obtain a frequency offset between the local oscillator signal and the received optical signal;
• and
• automatically tuning, by a controller of the coherent optical receiver, the tunable laser of the optical hybrid mixer to minimize the frequency offset obtained by the frequency offset correction estimator.

A coherent optical receiver comprising:

• an optical front end that receives an optical signal including a carrier signal modulated by a data signal, the optical front end including
• an optical hybrid mixer that mixes the received optical signal with a local oscillator signal to extract the data signal from the optical signal, and
• a photodetector to convert the extracted data signal to an electrical signal corresponding to the data signal;
• a digital modem coupled with the optical front end, the digital modem including
• an analog-to-digital converter that converts the electrical signal to digital data, and
• a frequency offset estimator that processes the digital data to obtain a frequency offset between the local oscillator signal and the received optical signal;
• and
• a controller that automatically adjusts a frequency of the local oscillator signal to minimize the frequency offset obtained by the frequency offset estimator.