We show that an iterative demodulation with soft-decision feedback information from FEC de-coder can efficiently mitigate cycle slips. With 3% pilot insertion, the turbo QPSK demodulation achieves 1.05dB gain even in the presence of frequent cycle slips. This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to… (More)
Fiber nonlinearity has become a major limiting factor to realize ultra-high-speed optical communications. We propose a fractionally-spaced equalizer which exploits a trained high-order statistics to deal with data-pattern dependent nonlinear impairments in fiber-optic communications. The computer simulation reveals that the proposed 3-tap equalizer improves… (More)
We propose a low-complexity turbo equalizer consisting of a sliding window MAP estimator, and a low overhead LDPC decoder. By utilizing 2nd order statistics, we obtain 2.5-4dB gain with additional improvement with turbo loop. This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part… (More)
Superchannel transmission is a candidate to realize Tb/s-class high-speed optical communications. In order to achieve higher spectrum efficiency, the channel spacing shall be as narrow as possible. However, densely allocated channels can cause nonnegligible inter-channel interference (ICI) especially when the channel spacing is close to or below the Nyquist… (More)
We propose to use Han-Kobayashi (HK) coding and dirty-paper coding (DPC) to cope with inter-carrier interference (ICI) in dual-carrier transmissions. We show the considerable benefit of those methods to increase throughput in presence of strong ICI for dense carrier spacing. This work may not be copied or reproduced in whole or in part for any commercial… (More)
We analyze demodulation methods for high-order QAM formats in the presence of quadrature angular skew caused by imperfect biasing of the transmitter. Proposed turbo demodulation improves skew tolerance of up to 33-degree angle for an SNR penalty of 1 dB for 1024QAM. This work may not be copied or reproduced in whole or in part for any commercial purpose.… (More)
We propose a fractionally-spaced equalizer with trained second-order statistics to deal with non-linear impairment in coherent optical communications. The proposed 3-tap equalizer improves Q-factor by more than 2 dB for long-haul transmissions of 5,230 km. This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission… (More)
A novel flip-flop based look-up-table is proposed for electronic digital signal processing, which can drastically reduce the circuit complexity. We evaluate the circuit size required to implement a 40 Gb/s electronic pre-equalizer using the proposed LUT.