Clock recovery from an optical signal with dispersion impairments
AssigneeNortel Networks Limited
InventorsHan Sun, Slobodan Jovanovic, Kuang Tsan Wu, Chandra Bontu, Kim B Roberts, Jianzhong Xu
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Abstract
A method of recovering a clock signal from an optical signal received through an optical communications system. A digital sample stream is processed to generate a dispersion compensated signal. The dispersion compensated signal is then tapped to obtain upper side band and lower side band signals of each received polarization of the optical signal. The upper side band and lower side band signals are then processed to compensate polarization dependent impairments, and the clock recovered from the resulting optimized.
Claims54
A method of recovering a clock signal from a high speed optical signal received through an optical communications network, the method comprising steps of:
- processing a stream of multi-bit digital samples of the optical signal to generate a dispersion compensated signal;
- and
- deriving a recovered clock signal using the dispersion compensated signal;
- wherein deriving the recovered clock signal comprises:
- selecting an upper side band (USB) and a lower side band (LSB) of the dispersion compensated signal;
- combining the USB and LSB signals to derive a composite signal value;
- and
- computing a phase error value from the composite signal value.
An apparatus for recovering a clock signal from a high speed optical signal received through an optical communications network, the apparatus comprising:
- a compensator for processing a stream of multi-bit digital samples of the optical signal to generate a dispersion compensated signal;
- and
- a signal processor for deriving a recovered clock signal using the dispersion compensated signal;
- wherein the signal processor comprises a phase detector for detecting a clock phase of the compensated signal, the phase detector comprising:
- means for combining an upper side band (USB) and a lower side band (LSB) of the compensated signal;
- and
- means for computing a phase error value from the composite signal value.
An optical communications system comprising:
- a receiver for receiving an optical signal and generating a corresponding multi-bit digital sample stream;
- a compensator for processing a stream of multi-bit digital samples of the optical signal to generate a dispersion compensated signal;
- and
- a signal processor for deriving a recovered clock signal using the dispersion compensated signal;
- wherein the signal processor comprises a phase detector for detecting a clock phase of the compensated signal, the phase detector comprising:
- means for combining an upper side band (USB) and a lower side band (LSB) of the compensated signal;
- and means for computing a phase error value from the composite signal value.
Dependencies are inferred from the claim text.