Forward error correction for an optical transport system

摘要

An optical transport system that transmits data using relatively short FEC-encoded data frames. The corresponding modulated optical signals are decoded at an optical receiver using frame-based maximum likelihood sequence estimation that relies on data redundancy present in each FEC-encoded data frame for the determination of its source bits. In some embodiments, the modulated optical signals carrying the FEC-encoded data frames are generated using a polarization-division-multiplexed constellation. The FEC-coding rate and frame length can be adjusted without changing the constellation, which advantageously enables the optical transport system to dynamically adapt its transmission format to the changing link conditions in a manner that results in better overall receiver sensitivity than that achieved with comparable bit-rate-adaptation methods that rely on a constellation change rather than on a change of the FEC-coding rate.

主权项

1. An apparatus comprising an optical receiver configured to:
convert a modulated optical signal corresponding to a first forward error correction (FEC)-encoded data frame into a first set of digital complex values that includes (i) a first subset of digital complex values corresponding to a first polarization of light and (ii) a second subset of digital complex values corresponding to a second polarization of light; apply maximum likelihood sequence estimation (MLSE) processing to the first set of digital complex values to determine an estimated set of constellation points of a polarization-division-multiplexed (PDM) constellation that corresponds to the modulated optical signal, wherein:
a first constellation point in said estimated set of constellation points corresponds to the first polarization of light and encodes a first source bit of the first FEC-encoded data frame; anda second constellation point in said estimated set of constellation points corresponds to the second polarization of light and encodes a parity bit of the first FEC-encoded data frame generated using the first source bit; and recover of source bits of the first FEC-encoded data frame from said estimated set of constellation points.