Abstract
There are three major advantages for coherent optical orthogonal frequency-division
multiplexing (CO-OFDM) transmission using digital signal processing. First,
coherent detection is realized by digital phase estimation without the need
for optical phase-locked loop. Second, OFDM modulation and demodulation are
realized by the well-established computation-efficient fast Fourier transform
(FFT) and inverse FFT. Third, adaptive data rates can be supported as different
quadrature amplitude modulation (QAM) constellations are software-defined,
without any hardware change in transmitter and receiver. However, it is well-known
that coherent detection, OFDM, and QAM are all susceptible to phase noise.
In this paper, theoretical, numerical, and experimental investigations are
carried out for phase noise effects on high spectral efficiency CO-OFDM transmission.
A transmission model in the presence of phase noise is presented. By using
simulation, the bit error rate floors from finite laser linewidth are presented
for CO-OFDM systems with high-order QAM constellations. In the experiments,
the phase noise effects from both laser linewidth and nonlinear fiber transmission
are investigated. The fiber nonlinearity mitigation based on receiver digital
signal processing is also discussed.
© 2008 IEEE
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