A Performance Investigation of Adaptive Phase Estimations in Coherent Optical Communications

We carried out a comprehensive analysis to examine the phase error variances in three adaptive phase estimation (PE) methods: the adaptive decision-aided PE, the Kalman PE, and the normalized least-mean square PE algorithms. The results show that they share the same phase error variances but with different approaches to determine the stepsize. Their performances in different quadrature amplitude modulation formats are analytically investigated for the purpose of determining the laser linewidth tolerance.