Systems and methods for error-free reconstruction of transmitted symbols in a coherent receiver

An apparatus configured to estimate a transmit symbol sequence implemented in a coherent receiver, the apparatus comprising:

• circuitry configured to receive a nominally error-free information bit sequence subsequent to Forward Error Correction (FEC) decoding;
• circuitry configured to determine a nominally error-free estimate of a transmitted bit sequence based on the nominally error-free information bit sequence;
• and
• circuitry configured to determine a nominally error-free estimate of the nominally error-free estimate of the transmit symbol sequence by mapping the transmitted bit sequence to transmit symbols, wherein the nominally error-free estimate of the transmit symbol sequence was transmitted by a corresponding coherent transmitter over a channel to the coherent receiver.

A coherent receiver configured to estimate a transmit symbol sequence, the coherent receiver comprising:

• a Forward Error Correction (FEC) decoding block configured to decode an input to provide a nominally error-free information bit sequence;
• a bit-monitor configured to monitor the nominally error-free information bit sequence to provide a nominally error-free estimate of a transmitted bit sequence;
• and
• a bit-to-symbol mapping block configured to map the nominally error-free estimate of the transmitted bit sequence to transmit symbols for a nominally error-free estimate of the transmit symbol sequence, wherein the nominally error-free estimate of the transmit symbol sequence was transmitted by a corresponding coherent transmitter over a channel to the coherent receiver.