Nonlinear Frequency-Division Multiplexing in the Focusing Regime

Achievable rates of the nonlinear frequency-division multiplexing (NFDM) and wavelength-division multiplexing (WDM) subject to the same power and bandwidth constraints are computed as a function of transmit power in the standard single-mode fiber. NFDM achieves higher rates than WDM.Comment: Invited paper to be presented at The Optical Fiber Communications Conference and Exposition (OFC), March 201

Linear and Nonlinear Frequency-Division Multiplexing

Two signal multiplexing schemes for optical fiber communication are considered: Wavelength-division multiplexing (WDM) and nonlinear frequency-division multiplexing (NFDM), based on the nonlinear Fourier transform. Achievable information rates (AIRs) of NFDM and WDM are compared in a network scenario with an ideal lossless model of the optical fiber in the defocusing regime. It is shown that the NFDM AIR is greater than the WDM AIR subject to a bandwidth and average power constraint, in a representative system with one symbol per user. The improvement results from nonlinear signal multiplexing

Capacity Lower Bounds of the Noncentral Chi-Channel with Applications to Soliton Amplitude Modulation

The channel law for amplitude-modulated solitons transmitted through a nonlinear optical fibre with ideal distributed amplification and a receiver based on the nonlinear Fourier transform is a noncentral chi-distribution with 2n degrees of freedom, where n = 2 and n = 3 correspond to the single- and dual-polarisation cases, respectively. In this paper, we study capacity lower bounds of this channel under an average power constraint in bits per channel use. We develop an asymptotic semi-analytic approximation for a capacity lower bound for arbitrary n and a Rayleigh input distribution. It is shown that this lower bound grows logarithmically with signal-to-noise ratio (SNR), independently of the value of n. Numerical results for other continuous input distributions are also provided. A half-Gaussian input distribution is shown to give larger rates than a Rayleigh input distribution for n = 1; 2; 3. At an SNR of 25 dB, the best lower bounds we developed are approximately 3:68 bit per channel use. The practically relevant case of amplitude shift-keying (ASK) constellations is also numerically analysed. For the same SNR of 25 dB, a 16- ASK constellation yields a rate of approximately 3:45 bit per channel use

Investigation into Information Capacity of Nonlinear Optical Fibre Communication Systems

The optical fibre is a ubiquitous transmission medium since it is able to provide both high speed and low loss. Optical fibre transmission systems carry 99% of the world’s telecommunication traffic. The emergence of new services and Internet applications gives rise to the exponentially increasing demand for higher transmission data rates, motivating the search for new methods to enhance the capacity of optical fibre systems. However, due to the presence of power-dependent signal degradation effects (the optical Kerr effects) together with bandwidth limitations constrained by the low-loss region of the fibre, the current optical fibre communication infrastructure is unable to cope with the ever-growing demand for data rates. The capacity of an optical fibre channel remains unknown and is an open research question. The PhD research described in this thesis aimed to theoretically investigate the capacity of the nonlinear optical fibre channel using information-theoretic tools with the view to improving information data rates of optical fibre networks. The first part of the thesis is concerned with a comprehensive study of Kerr nonlinearity-compensated dispersion unmanaged ultra-wide bandwidth optical fibre communication systems. The bounds on information rate, based on the proposed model, which takes into account the fundamental limitations due to nonlinear interactions between optical signal and amplifier noise, were accurately estimated. The second part deals with the application of the so-called integrability property (the general ideas based around nonlinear Fourier transform (NFT)) of a lossless and noiseless nonlinear Schrödinger equation (NLSE). A new non-Gaussian channel model for soliton-based transmission, in which data is assumed to be embedded into the imaginary part of the nonlinear discrete spectrum was proposed for the first time. New asymptotic semi-analytic approximations for non-decaying capacity bounds have been derived. The theoretical results of this research can be considered as an important first step towards the ultimate capacity limits of nonlinear optical communication links

Nonlinear frequency-division multiplexing in the focusing regime

\u3cp\u3eAchievable rates of the nonlinear frequency-division multiplexing (NFDM) and wavelength-division multiplexing (WDM) subject to the same power and bandwidth constraints are computed as a function of transmit power in the standard single-mode fiber. NFDM achieves higher rates than WDM.\u3c/p\u3