Carrier phase estimation schemes with bit-error-rate independent and modulation format transparency

Low complexity carrier phase estimation (CPE) with bit-error-rate independent and modulation format transparency is very important for coherent optical communication receiver, and is still a challenge task. We propose a series of schemes of good performance and low complexity CPE, including an optical pilot-tone-added (PA) method and a crossed constellation transformation (CCT) algorithm, which are proved to be linewidth tolerant, bit-error-rate independent, modulation format transparent, and low complexity. We introduce an optical pilot-tone-added CPE scheme for a dual-carrier Nyquist m-QAM system. We also present a multi-stage CPE scheme based on CCT for either the square-frame m-QAM like 64QAM or the non-square-frame m-QAM like 32-QAM and 128-QAM.