In this paper, we reviewed our common phase
error (CPE) and intercarrier interference (ICI) compensa-
tion methods for coherent optical orthogonal frequency
division multiplexing (CO-OFDM) system. We first
presented a unified CPE estimation framework combining
decision-aided (DA), pilot-aided (PA) and decision feed-
back (DF) algorithms. The DA method is used to estimate
the CPE of the current OFDM symbol based on the
decision statistics of the previous symbol. DA + PA helps
increase the phase noise tolerance of DA and reduce the
overhead of PA, while DA + DF reduces the overhead to
zero, achieving best performance with one more step of
estimation, compensation and demodulation. We also
described a modified time-domain blind intercarrier
interference (BL-ICI) mitigation algorithm over non-
constant amplitude formats. The new algorithm is derived
from the BL-ICI algorithm over constant amplitude format
for wireless networks. A new power estimation scheme
was proposed for the BL-ICI algorithm to adapt to non-
constant amplitude format. It has the same order of
complexity with frequency domain decision-aided ICI
(DA-ICI) compensation method and does not suffer from
symbol decision errors. The effectiveness of both CPE and
ICI compensation algorithms were demonstrated in a
simulated 56-Gbit/s CO-OFDM system with various
modulation formats.

• Carrier recovery in coherent receiver of optical orthogonal frequency division multiplexing system