Soft decoding of data in a coherent optical receiver
AssigneeCiena Corporation
InventorsAmir Keyvan KHANDANI, Han SUN, Kim B. ROBERTS
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Abstract
In a coherent optical receiver receiving a polarization multiplexed optical signal through an optical communications network, a method of compensating noise due to polarization dependent loss (PDL). A Least Mean Squares (LMS) compensation block processes sample streams of the received optical signal to generate symbol estimates of symbols modulated onto each transmitted polarization of the optical signal. A decorrelation block de-correlates noise in the respective symbol estimates of each transmitted polarization and generating a set of decorrelated coordinate signals. A maximum likelihood estimator soft decodes the de-correlated coordinate signals generated by the decorrelation block.
Claims20
In an optical communications network comprising a transmitter and a coherent optical receiver, the transmitter transmitting an optical signal having a predetermined polarization state and symbols modulated onto two orthogonal transmitted polarizations, the coherent optical receiver processing the optical signal and recovering respective symbol estimates of the modulated symbols, a method of compensating polarization dependent loss (PDL), the method comprising:
- a processor computing an estimate representative of a noise polarization of the optical signal received by the coherent optical receiver;
- the transmitter adjusting the polarization state of the transmitted optical signal using the computed estimate;
- and
- a decorrelation block of the receiver minimizing a noise correlation between the two orthogonal received polarizations of the symbol estimates and generating a set of decorrelated signals, wherein the noise correlation is a correlation between noise in one received polarization and noise in the other received polarization of each symbol estimate.
A system for compensating polarization dependent loss (PDL) in an optical communications network, the system comprising:
- the transmitter for transmitting an optical signal having a predetermined polarization state and symbols modulated onto two orthogonal transmitted polarizations of the optical signal;
- a coherent optical receiver for processing the optical signal and recovering respective dual-polarization symbol estimates of the modulated symbols, the receiver comprising:
- a processor for computing an estimate representative of a noise polarization of the optical signal received by the coherent optical receiver;
- and
- a decorrelation block for minimizing a noise correlation between two orthogonal received polarizations of the symbol estimates and generating a set of decorrelated signals, wherein the noise correlation is a correlation between noise in one received polarization and noise in the other received polarization of each symbol estimate;
- the transmitter adjusting the polarization state of the transmitted optical signal using the computed estimate.
Dependencies are inferred from the claim text.