Abstract
We review and study several single carrier based multi-level and
multi-dimensional coding (ML-MDC) technologies recently demonstrated for
spectrally-efficient 100-Gb/s transmission. These include 16-ary PDM-QPSK,
64-ary PDM-8PSK, 64-ary PDM-8QAM as well as 256-ary PDM-16 QAM. We show that
high-speed QPSK, 8PSK, 8QAM, and 16QAM can all be generated using
commercially available optical modulators using only binary electrical drive
signals through novel synthesis methods, and that all of these modulation
formats can be detected using a universal receiver front-end and digital
coherent detection. We show that the constant modulus algorithm (CMA), which
is highly effective for blind polarization recovery of PDM-QPSK and PDM-8PSK
signals, is much less effective for PDM-8QAM and PDM-16 QAM. We then present
a recently proposed, cascaded multi-modulus algorithm for these cases. In
addition to the DSP algorithms used for constellation recovery, we also
describe a DSP algorithm to improve the performance of a coherent receiver
using single-ended photo-detection. The system impact of ASE noise, laser
phase noise, narrowband optical filtering and fiber nonlinear effects has
been investigated. For high-level modulation formats using full
receiver-side digital compensation, it is shown that the requirement on LO
phase noise is more stringent than the signal laser. We also show that RZ
pulse shaping significantly improves filter- and fiber-nonlinear tolerance.
Finally we present three high-spectral-efficiency and high-speed DWDM
transmission experiments implementing these ML-MDC technologies.
© 2009 IEEE
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