Patent Document ID: 20120263464
Application ID: 13085715
Patent Flag: 0

Claim One:
1. A method for canceling cross-polarization modulation (XPolM) adaptively in a coherent optical communication system, comprising the steps of: forward maximum-likelihood sequence estimation (MLSE) decoding, which comprises the steps of decoding jointly x-polarization and y-polarization signals concurrently along a joint trellis-state diagram using a Viterbi process; estimating crosstalk channels along survivor paths of the Viterbi process using 1-side exponential weighted recursive least-squares (RLS) process; and memorizing estimated channels, cross-correlation, auto-correlation, and decoded data for every state along the survivor paths; and backward MLSE decoding, which comprises the steps of decoding x-polarization and y-polarization signals jointly along the reverse time direction of the joint trellis-state diagram using the Viterbi process; estimating crosstalk channels along a reverse time direction of the survivor paths in the joint trellis-state diagram using 2-side exponential weighted RLS, which uses newly computed cross-correlation matrix and the memorized cross-correlation matrix at the forward MLSE decoding; and calculating channel covariance matrix based on the estimated crosstalk channel matrices for the ML path; MLSE-RLS decoding, which comprises the steps of: decoding the x-polarization and y-polarization signals jointly along a joint trellis-state diagram using the Viterbi process; estimating a time-varying crosstalk channels for the survivor path, or using an optimum-weighted RLS process, which uses a previously computed channel covariance matrix to improve tracking capability, wherein the steps are performed in a cross-talk canceller.