78 research outputs found
Comparison of Linear and Nonlinear Equalization for Ultra-High Capacity Spectral Superchannels
In ultra-high-speed (>400Gb/s per wavelength), high-spectral efficiency coherent optical communication systems using multi-carrier spectral superchannels, the maximum reach is severely limited due to linear and, foremost, nonlinear impairments. Hence, the implementation of advanced digital signal processing (DSP) techniques in optical transceivers is crucial for alleviating the impact of such impairments. However, the DSP performance improvement comes at the expense of increased cost and power consumption. Given that the computational complexity of the applied linear and nonlinear equalizers is the factor that determines the trade-off between the performance improvement and cost, in this study we provide an extended analysis on the computational complexity of various linear and nonlinear equalization approaches. First, we draw a complexity comparison between a conventional OFDM coherent receiver versus a filter-bank based OFDM receiver and it is shown that the latter provides significant complexity savings. Second, we present a comparison between the digital back-propagation split-step Fourier (DBP-SSF) method and the inverse Volterra series transfer function nonlinear equalizer (IVSTF-NLE) in terms of performance and computational complexity for a 32 Gbaud polarization multiplexed (PM)-16 quadrature amplitude modulation (QAM) OFDM superchannel
Mode-Dependent Loss and Gain: Statistics and Effect on Mode-Division Multiplexing
In multimode fiber transmission systems, mode-dependent loss and gain
(collectively referred to as MDL) pose fundamental performance limitations. In
the regime of strong mode coupling, the statistics of MDL (expressed in
decibels or log power gain units) can be described by the eigenvalue
distribution of zero-trace Gaussian unitary ensemble in the small-MDL region
that is expected to be of interest for practical long-haul transmission.
Information-theoretic channel capacities of mode-division-multiplexed systems
in the presence of MDL are studied, including average and outage capacities,
with and without channel state information.Comment: 22 pages, 8 figure
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Covariance Clustering: Modelling Covariance in Designed Experiments When the Number of Variables is Greater than Experimental Units
The size and complexity of datasets resulting from comparative research experiments in the agricultural domain is constantly increasing. Often the number of variables measured in an experiment exceeds the number of experimental units composing the experiment. When there is a necessity to model the covariance relationships that exist between variables in these experiments, estimation difficulties can arise due to the resulting covariance structure being of reduced rank. A statistical method, based in a linear mixed model framework, is presented for the analysis of designed experiments where datasets are characterised by a greater number of variables than experimental units, and for which the modelling of complex covariance structures between variables is desired. Aided by a clustering algorithm, the method enables the estimation of covariance through the introduction of covariance clusters as random effects into the modelling framework, providing an extension of the traditional variance components model for building covariance structures. The method was applied to a multi-phase mass spectrometry-based proteomics experiment, with the aim of exploring changes in the proteome of barley grain over time during the malting process. The modelling approach provides a new linear mixed model-based method for the estimation of covariance structures between variables measured from designed experiments, when there are a small number of experimental units, or observations, informing covariance parameter estimates
The Real Symplectic Groups in Quantum Mechanics and Optics
text of abstract (We present a utilitarian review of the family of matrix
groups , in a form suited to various applications both in optics
and quantum mechanics. We contrast these groups and their geometry with the
much more familiar Euclidean and unitary geometries. Both the properties of
finite group elements and of the Lie algebra are studied, and special attention
is paid to the so-called unitary metaplectic representation of .
Global decomposition theorems, interesting subgroups and their generators are
described. Turning to -mode quantum systems, we define and study their
variance matrices in general states, the implications of the Heisenberg
uncertainty principles, and develop a U(n)-invariant squeezing criterion. The
particular properties of Wigner distributions and Gaussian pure state
wavefunctions under action are delineated.)Comment: Review article 43 pages, revtex, no figures, replaced because
somefonts were giving problem in autometic ps generatio
Experimental Observation of Quantum Chaos in a Beam of Light
The manner in which unpredictable chaotic dynamics manifests itself in
quantum mechanics is a key question in the field of quantum chaos. Indeed, very
distinct quantum features can appear due to underlying classical nonlinear
dynamics. Here we observe signatures of quantum nonlinear dynamics through the
direct measurement of the time-evolved Wigner function of the quantum-kicked
harmonic oscillator, implemented in the spatial degrees of freedom of light.
Our setup is decoherence-free and we can continuously tune the semiclassical
and chaos parameters, so as to explore the transition from regular to
essentially chaotic dynamics. Owing to its robustness and versatility, our
scheme can be used to experimentally investigate a variety of nonlinear quantum
phenomena. As an example, we couple this system to a quantum bit and
experimentally investigate the decoherence produced by regular or chaotic
dynamics.Comment: 7 pages, 5 figure
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