Method and system for optical impairments mitigation for high-speed optical communication systems

1. A method comprising:

compensating a signal using a linear filter thereby generating a first compensated signal;

conducting a polarization recovery and residual dispersion compensation of the first compensated signal using an adaptive equalizer having a first adaptation rate thereby generating a second compensated signal;

estimating a frequency offset by conducting a carrier frequency recovery of the second compensated signal and removing the frequency offset using a one-tap filter thereby generating a frequency-recovered signal;

performing a phase recovery of the frequency-recovered signal using a fast-adaptive multi-tap digital filter with coefficients estimated based on a reference signal to generate a phase-recovered signal, the reference signal determined by removing an estimate of a carrier phase from the frequency-recovered signal; and

demodulating the phase-recovered signal.

2. The method of claim 1 , wherein the fast-adaptive multi-tap digital filter has a second adaptation rate that exceeds the first adaptation rate.

3. The method of claim 2 , wherein performing a phase recovery further comprises:

dividing the frequency-recovered signal into a plurality of data blocks;

estimating the carrier phase for each of the plurality of data blocks using a common phase estimation algorithm;

removing the estimate of the carrier phase estimated from each of the plurality of data blocks using the fast-adaptive multi-tap digital filter;

identifying the reference signal within each of the plurality of data blocks, wherein the reference signal is the phase-recovered signal;

estimating the coefficients of the fast-adaptive multi-tap digital filter using the reference signal;

updating the coefficients of the fast-adaptive multi-tap digital filter;

equalizing the frequency-recovered signal using the fast-adaptive multi-tap digital filter with the coefficients updated thereby generating an equalized signal; and

identifying the equalized signal.

4. The method of claim 2 , wherein the second adaptation rate is generated by a feed-forward-based adaptation algorithm.

5. The method of claim 1 , wherein the signal comprises a digitized signal at a first orthogonal polarization and a digitized signal at a second orthogonal polarization.

6. The method of claim 1 , wherein the frequency offset is a signal frequency offset between a source of the signal and a local oscillator.

7. The method of claim 1 , wherein demodulating the phase-recovered signal comprises inputting the phase-recovered signal into a signal decision unit.

8. An apparatus comprising:

a processor; and

a memory to store computer program instructions, the computer program instructions when executed on the processor, cause the processor to perform operations comprising:

compensating a signal using a linear filter thereby generating a first compensated signal;

conducting a polarization recovery and residual dispersion compensation of the first compensated signal using an adaptive equalizer having a first adaptation rate thereby generating a second compensated signal;

estimating a frequency offset by conducting a carrier frequency recovery of the second compensated signal and removing the frequency offset using a one-tap filter thereby generating a frequency-recovered signal;

performing a phase recovery of the frequency-recovered signal using a fast-adaptive multi-tap digital filter with coefficients estimated based on a reference signal to generate a phase-recovered signal, the reference signal determined by removing an estimate of a carrier phase from the frequency-recovered signal; and

demodulating the phase-recovered signal.

9. The apparatus of claim 8 , wherein the fast-adaptive multi-tap digital filter has a second adaptation rate that exceeds the first adaptation rate.

10. The apparatus of claim 9 , wherein performing a phase recovery further comprises:

dividing the frequency-recovered signal into a plurality of data blocks;

estimating the carrier phase for each of the plurality of data blocks using a common phase estimation algorithm;

removing the estimate of the carrier phase estimated from each of the plurality of data blocks using the fast-adaptive multi-tap digital filter;

identifying the reference signal within each of the plurality of data blocks, wherein the reference signal is the phase-recovered signal;

estimating the coefficients of the fast-adaptive multi-tap digital filter using the reference signal;

updating the coefficients of the fast-adaptive multi-tap digital filter;

equalizing the frequency-recovered signal using the fast-adaptive multi-tap digital filter with the coefficients updated thereby generating an equalized signal; and

identifying the equalized signal.

11. The apparatus of claim 9 , wherein the second adaptation rate is generated by a feed-forward-based adaptation algorithm.

12. The apparatus of claim 8 , wherein the signal comprises a digitized signal at a first orthogonal polarization and a digitized signal at a second orthogonal polarization.

13. The apparatus of claim 8 , wherein demodulating the phase-recovered signal comprises inputting the phase-recovered signal into a signal decision unit.

14. A computer readable medium storing computer program instructions for optical impairment mitigation, which, when executed on a processor, cause the processor to perform operations comprising:

compensating a signal using a linear filter thereby generating a first compensated signal;

conducting a polarization recovery and residual dispersion compensation of the first compensated signal using an adaptive equalizer having a first adaptation rate thereby generating a second compensated signal;

estimating a frequency offset by conducting a carrier frequency recovery of the second compensated signal and removing the frequency offset using a one-tap filter thereby generating a frequency-recovered signal;

performing a phase recovery of the frequency-recovered signal using a fast-adaptive multi-tap digital filter with coefficients estimated based on a reference signal to generate a phase-recovered signal, the reference signal determined by removing an estimate of a carrier phase from the frequency-recovered signal; and

demodulating the phase-recovered signal.

15. The computer readable medium of claim 14 , wherein the fast-adaptive multi-tap digital filter has a second adaptation rate that exceeds the first adaptation rate.

16. The computer readable medium of claim 15 , wherein performing a phase recovery further comprises:

dividing the frequency-recovered signal into a plurality of data blocks;

estimating the carrier phase for each of the plurality of data blocks using a common phase estimation algorithm;

removing the estimate of the carrier phase estimated from each of the plurality of data blocks using the fast-adaptive multi-tap digital filter;

identifying the reference signal within each of the plurality of data blocks, wherein the reference signal is the phase-recovered signal;

estimating the coefficients of the fast-adaptive multi-tap digital filter using the reference signal;

updating the coefficients of the fast-adaptive multi-tap digital filter;

equalizing the frequency-recovered signal using the fast-adaptive multi-tap digital filter with the coefficients updated thereby generating an equalized signal; and

identifying the equalized signal.

17. The computer readable medium of claim 15 , wherein the second adaptation rate is generated by a feed-forward-based adaptation algorithm.

18. The computer readable medium of claim 14 , wherein the signal comprises a digitized signal at a first orthogonal polarization and a digitized signal at a second orthogonal polarization.

19. The computer readable medium of claim 14 , wherein demodulating the phase-recovered signal comprises inputting the phase-recovered signal into a signal decision unit.

20. The computer readable medium of claim 14 , wherein the frequency offset is a signal frequency offset between a source of the signal and a local oscillator.