Application of digital signal processing in coherent optical communication systems

Abstract

In this thesis, we study the application of DSP techniques in optical coherent communication systems and propose a few algorithms to improve receiver performance.

An accurate two-stage frequency offset estimation (FOE) algorithm is introduced, whose mean square error (MSE) is two orders less than that of the conventional phase difference-based FOE.

A low complexity phase interpolation filter is proposed for block-averaging carrier phase estimation (CPE) algorithms. The performance of block estimation with proposed filter is similar to that of the sliding-window estimation.

An adaptive joint-polarization carrier phase recovery algorithm is proposed to estimate FO and carrier phase in one block to reduce complexity. Signals from both polarizations are jointly processed for better noise immunity.

A decision-aided CPE with selective averaging is introduced. Symbols with significantly large noise are identified and excluded to reduce estimation distortion.

Finally, a DSP-based receiver for coherent long-reach optical access network is studied. Issues such as Burst-mode clock data recovery and frequency chirp mitigation are addressed.