Chromatic dispersion-aware Tx and LO laser phase noise independent estimation enabled by dual pilot tones in DSCM systems.

In the backbone networks employing high modulation formats such as 64QAM and metropolitan area networks, data center interconnection networks using the distributed feedback (DFB) lasers with several megahertz laser linewidths dramatically degrades system performance in the equalization enhanced phase noise (EEPN). Even though digital subcarrier multiplexing (DSCM) systems are known for their tolerance to EEPN, they still cause performance degradation in this case. Therefore, the EEPN mitigation algorithm becomes an indispensable part of DSP algorithms in DSCM systems. A dual pilot tone-based chromatic dispersion-aware transmitter and local oscillator laser phase noise independent estimation algorithm is proposed in this paper to solve the above problem. Simulations/offline experiment results under 5 MHz laser linewidth and 1000/800 km transmission indicate that the proposed algorithm could bring about 1/0.6 dB improvement of the required SNR for the normalized generalized mutual information of 0.9 compared with the blind phase searching algorithm.