Pilot data aided feed forward (PAFF) carrier
recovery is essential for phase noise tracking in coherent
optical receivers. This paper describes a new PAFF system
based on new pilot arrangement and maximum likelihood
(ML) to estimate the phase jitter in coherent receiver-
induced by local oscillator’s lasers and sampling clock
errors. Square M-ary quadrature amplitude modulation
(M-QAM) (4, 16, 64, and 256) schemes were used. A
detailed mathematical description of the method was
presented. The system performance was evaluated through
numerical simulations and compared to those with noise-
free receiver (ideal receiver) and feed forward without ML.
The simulation results show that PAFF performs near the
expected ideal phase recovery. Results clearly suggest that
ML significantly improves the tolerance of phase error
variance. From bit error rate (BER) sensibility evaluation,
it was clearly observed that the new estimation method
performs better with a 4-QAM (or quadrature phase shift
keying (QPSK)) format compared to three others square
QAM schemes. Analog to digital converter (ADC)
resolution effect on the system performance was analyzed
in terms of Q-factor. Finite resolution effect on 4-QAM is
negligible while it negatively affects the system perfor-
mance when M increases.

EB00000002099K

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• Improved pilot data aided feed forward based on maximum likelihood for carrier phase jitter recovery in coherent optical orthogonal frequency division multiplexing