Performance Comparison of MLSE and Iterative Equalization in FEC Systems for PMD Channels with Respect to Implementation Complexity

Complex electronic signal processing for high bitdate lightwave systems has become available recently. Adaptive receiver concepts are proposed to mitigate dynamic changes in the optical channel response. In particular two different approaches are under discussion: independent equalization and decoding, e.g., by maximum-likelihood sequence estimation (MLSE) followed by a separate error correction decoder, and a combined approach by iterative decoding of the channel correlations and the error correction code. We compare the two concepts with respect to their mitigation capabilities in the presence of polarization mode dispersion (PMD). Special attention is paid to implementation apsects of the electronic concepts, since application is severely limited by memory and signal processing requirements.