Adaptive equalization combined with maximum likelihood decoder for trellis code modulation based on high-order QAM signals

Laser phase noise remarkably degrades the bit-error-ratio (BER) characteristics of Trellis code modulation (TCM) signals based on high-order QAM constellation. In order to suppress phase noise, we propose to combine adaptive equalization with maximum likelihood estimation for TCM decoding. With our scheme, we experimentally evaluate the BER characteristics of dual-polarization 64QAM-based TCM optical signals. The results suggests that our scheme is effective to suppress the BER degradation due to phase noise for TCM signals based on high-order-QAM constellation.