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Channel-Aware Multilevel Coded Modulation for Coherent Fiber-Optic Communications

Lotfollah Beygi (Institutionen för signaler och system, Kommunikationssystem)
Göteborg : Chalmers University of Technology, 2013. ISBN: 978-91-7385-873-1.- 188 s.
[Doktorsavhandling]

The past decades have shown an ever-increasing demand for high-rate Internet services, motivating a great effort to increase the spectral efficiency of optical networks. In general, fiber-optic links are non-Gaussian, and in contrast to additive white Gaussian noise (AWGN) channels, there is no standard framework for quantifying fundamental limits or designing capacity-approaching coding schemes for such channels. In this thesis, some steps are taken toward this challenging goal by first developing a channel model for fiber-optic links and, second, using an information-theoretic design framework to investigate joint design of forward error correction and multilevel modulation, so-called coded modulation (CM), techniques for these channels. We extend the signal statistics of highly nonlinear single-polarization fiber-optic links with negligible dispersion to the polarization-multiplexed case. Taking chromatic dispersion into account, we derive an analytical discrete-time model for single- wavelength, polarization-multiplexed, non-dispersion-managed (non-DM) links. According to this model, for high enough symbol rates, a fiber-optic link can be described as a linear dispersive channel with AWGN and a complex constant scaling. We exploit the proposed channel model for highly nonlinear fiber-optic links to devise a new channel-aware multilevel CM scheme based on the minimization of the total block error rate. We introduce a CM system with an N-dimensional constellation constructed from the Cartesian product of N identical one-dimensional constellations. The multidimensional scheme shows better trade-off between complexity and performance than a one-dimensional multilevel CM scheme. By invoking the introduced channel model for the dispersive non-DM links, we present a four-dimensional CM scheme, which shows a better trade-off between digital signal processing complexity and transparent reach than existing methods. This CM scheme together with a probabilistic signal shaping method is used to devise a rate-adaptive scheme with a single low-density parity-check code. The performance evaluation of the proposed CM scheme for a single-channel transmission fiber-optic system justifies the improvement of the system spectral efficiency for a wide range of transparent reaches, observing more than 1 dB performance gain compared to existing methods.

Nyckelord: Fiber-optic communications, channel model, nonlinear phase noise, low-complexity de- tector, coded modulation, multidimensional set partitioning, signal statistics.



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Denna post skapades 2013-07-30. Senast ändrad 2013-09-25.
CPL Pubid: 180366