Abstract
An enhanced digital coherent receiver including a novel blind equalization
approach and maximum-likelihood sequence detection (MLSD) is proposed for
dual-polarization quadrature duobinary (DP-QDB) systems. In virtue of the
compact spectrum of DP-QDB signals approaching Nyquist limit, the equalization
is implemented at symbol rate, which relaxes the demand on the sampling speed
of analog-to-digital converters (ADCs). The proposed symbol-rate receiver
is verified by 43Gb/s experiments in the presence of chromatic
dispersion and polarization-mode dispersion. This paper also investigates
the tolerances to narrowband optical filtering, ADC sampling phase, duobinary-generating
filter bandwidth, laser linewidth, and carrier frequency offset. Detailed
modulation format comparisons are made among DP-QDB, DP-quadrature-phase-shift
keying (QPSK), DP-8 quadrature amplitude modulation (QAM), and DP-16QAM. It
is shown that DP-QDB with MLSD well trades off major requirements on advanced
modulation formats.
© 2011 IEEE
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