Wavelength-tunable burst-mode receiver

1. An apparatus, comprising:

an optical front end configured to coherently receive an input optical signal and convert the input optical signal to a digital-electrical data stream; and

a receiver processor configured to:

recover a data stream from the digital-electrical data stream;

and

cross-correlate first and second received complex correlation patterns with first and second pre-determined correlation patterns; and

determine, from the comparison, coefficients of a filter configured to recover data encoded on the input digital-electrical data stream.

2. The apparatus of claim 1 , wherein the filter is configured to recover DP-QPSK modulated data from the digital-electrical signal.

3. The apparatus of claim 1 , wherein:

the optical front end comprises an optical hybrid configured to receive an input optical signal and a local oscillator signal and to produce a plurality of optical output signals corresponding to in-phase and quadrature components of the input optical signal;

a plurality of optical detectors are each configured to convert a corresponding one of the optical output signals to a corresponding electrical signal; and

a plurality of analog-to-digital converters are configured to produce, from the outputs of the optical detectors, the digital-electrical data stream including the in-phase and quadrature components.

4. The apparatus of claim 3 , wherein the local oscillator signal is configured to switch between first and second wavelengths.

5. The apparatus of claim 3 , wherein the receiver processor is further configured to reduce a relative polarization angle between the input optical signal and the local oscillator signal by reducing a measure of cross-correlation between a received correlation pattern corresponding to a first polarization channel of the input optical signal bandwidth and a predetermined correlation pattern corresponding to a second polarization channel of the input optical signal.

6. The apparatus of claim 3 , wherein the first and second pre-determined correlation patterns correspond to about nil rotation between a polarization channel of the received optical signal and a corresponding polarization of the local oscillator.

7. The apparatus of claim 3 , wherein the receiver processor is further configured to separate two polarization data channels received via the input optical signal.

8. The apparatus of claim 3 , wherein the receiver processor is further configured to reduce an offset frequency between the input optical signal and the local oscillator prior to the cross-correlation.

9. The apparatus of claim 8 , wherein the receiver processor is further configured to reduce the offset frequency by determining the offset frequency, between data packets conveyed by the input optical signal, during a header period during which the input optical signal is unmodulated.

10. A method, comprising:

configuring a receiver processor of an optical coherent receiver to:

recover a data stream from an input digital-electrical data stream;

cross-correlate first and second received complex correlation patterns with first and second pre-determined correlation patterns; and

determine, from the correlation, coefficients of a filter configured to recover data encoded on the input digital-electrical data stream.

11. The method of claim 10 , further comprising configuring the filter to recover DP-QPSK modulated data from the digital-electrical signal.

12. The method of claim 10 , further comprising:

configuring an optical hybrid to receive an input optical signal and a local oscillator signal and to produce a plurality of optical output signals corresponding to in-phase and quadrature components of the input optical signal;

configuring each optical detector of a plurality of optical detectors to convert a corresponding one of the output signals to a corresponding electrical signal; and

configuring a plurality of analog-to-digital converters to produce, from the outputs of the optical detectors, the digital-electrical data stream including the in-phase and quadrature components.

13. The method of claim 12 , wherein the local oscillator signal is configured to switch between first and second wavelengths.

14. The method of claim 12 , wherein the receiver processor is further configured to reduce a relative polarization angle between the input optical signal and the local oscillator signal by reducing a measure of cross-correlation between a received correlation pattern corresponding to a first polarization channel of the input optical signal bandwidth and a predetermined correlation pattern corresponding to a second polarization channel of the input optical signal.

15. The method of claim 12 , wherein the correlation includes wherein the first and second pre-determined correlation patterns correspond to about nil rotation between a polarization channel of the received optical signal and a corresponding polarization of the local oscillator.

16. The method of claim 12 , wherein the receiver processor is further configured to separate two polarization data channels received via the input optical signal.

17. The method of claim 12 , wherein the receiver processor is further configured to reduce an offset frequency between the input optical signal and the local oscillator prior to the cross-correlation.

18. The method of claim 17 , wherein the receiver processor is further configured to reduce the offset frequency by determining the offset frequency, between data packets conveyed by the input optical signal, during a header period during which the input optical signal is unmodulated.