Time varying ISI model for nonlinear interference noise

We show that the effect of nonlinear interference in WDM systems is equivalent to slowly varying inter-symbol-interference (ISI), and hence its cancellation can be carried out by means of adaptive linear filtering. We characterize the ISI coefficients and discuss the potential gain following from their cancellation.Comment: Submitted to the optical fiber communication conference (OFC), 201

Polarization Drift Channel Model for Coherent Fibre-Optic Systems

A theoretical framework is introduced to model the dynamical changes of the state of polarization during transmission in coherent fibre-optic systems. The model generalizes the one-dimensional phase noise random walk to higher dimensions, accounting for random polarization drifts, emulating a random walk on the Poincar\'e sphere, which has been successfully verified using experimental data. The model is described in the Jones, Stokes and real four-dimensional formalisms, and the mapping between them is derived. Such a model will be increasingly important in simulating and optimizing future systems, where polarization-multiplexed transmission and sophisticated digital signal processing will be natural parts. The proposed polarization drift model is the first of its kind as prior work either models polarization drift as a deterministic process or focuses on polarization-mode dispersion in systems where the state of polarization does not affect the receiver performance. We expect the model to be useful in a wide-range of photonics applications where stochastic polarization fluctuation is an issue.Comment: 15 pages, 4 figure

Improved Lower Bounds on Mutual Information Accounting for Nonlinear Signal-Noise Interaction

In fiber-optic communications, evaluation of mutual information (MI) is still an open issue due to the unavailability of an exact and mathematically tractable channel model. Traditionally, lower bounds on MI are computed by approximating the (original) channel with an auxiliary forward channel. In this paper, lower bounds are computed using an auxiliary backward channel, which has not been previously considered in the context of fiber-optic communications. Distributions obtained through two variations of the stochastic digital backpropagation (SDBP) algorithm are used as auxiliary backward channels and these bounds are compared with bounds obtained through the conventional digital backpropagation (DBP). Through simulations, higher information rates were achieved with SDBP, {which can be explained by the ability of SDBP to account for nonlinear signal--noise interactionsComment: 8 pages, 5 figures, accepted for publication in Journal of Lightwave Technolog

Practical Detection Schemes for Power Efficient Modulation Formats

We discuss the detection process for a selection of power efficient formats. The receiver subsystems of dynamic equalization, phase estimation, and data detection are described with emphasis on the case with differential encoding

Perturbation Analysis of Nonlinear Propagation in a Strongly Dispersive Optical Communication System

We discuss an analytical model that predicts the impact of the Kerr nonlinearity in optical communication systems when the signal spectrum is wide and the accumulated dispersion during propagation is large. A detailed derivation of this model is given for a generalized system by means of a perturbation analysis of the Manakov equation with attenuation, gain, and third order dispersion included. As in the case with previous studies, three simplifying assumptions are necessary. These are that (i) the nonlinearity is weak, (ii) the input signal is of a given specific form, and (iii) the signal-noise interaction can be neglected. Under these assumptions, the result is found exactly. We also discuss the accuracy of the analytical result and show that third order dispersion has a small impact in practice

Societal Entrepreneurship as a Lever to Sustainable Local and Regional Development - the Case of the ALV Theme park

When the need for development goes beyond economic growth to include also ecological, social and cultural concerns, the means must be broadened beyond financial capital to include also human, social and emotional capital. While human capital concern the intellectual capabilities that people have in term of formal and personal knowledge, social capital refers to the resources that they have access to thanks to their personal networks. Emotional capital is more seldom considered by includes the ability of people to get committed, to engage and passionately get involved in the enactment of own ideas or the protecting the local community from being deconstructed. There are two major strategies to cope with a need for sustainable development - (inter)action or reaction. The last-mentioned creates correctives to the negative consequences of economic focus in present operations. Corporate Social Responsibility (CSR) may be considered as such a corrective. The first-mentioned strategy is an integrated approach to the making of a sustainable organization/locality in a way where economic, social and ecological as well as cultural forces and pressures spontaneously and interactively build a texture out of micro-events which attracts and support further measures. As much as market-oriented research is the obvious point of departure for strategies that guide economic change, social or societal entrepreneurship is an appropriate frame for the proposed integrated approach. The field study concerns Astrid Lindgren's World where the stories told by world-famous Swedish writer of children's books, e.g. Pippi Longstocking are enacted in park in the vicinity of the small town Vimmerby in Southern Sweden. Both the messages communicated by the books/stories and the author's deep involvement in the management of the park reflected a concern for more generic values than the making of a business venture. We will demonstrate that the making of the park into one of Sweden's most attractive destinations for domestic as well as international visitors is the outcome of multiple agency originating in all three sectors.

Modeling of Nonlinear Signal Distortion in Fiber-Optic Networks

A low-complexity model for signal quality prediction in a nonlinear fiber-optic network is developed. The model, which builds on the Gaussian noise model, takes into account the signal degradation caused by a combination of chromatic dispersion, nonlinear signal distortion, and amplifier noise. The center frequencies, bandwidths, and transmit powers can be chosen independently for each channel, which makes the model suitable for analysis and optimization of resource allocation and routing in large-scale optical networks applying flexible-grid wavelength-division multiplexing

Stochastic Digital Backpropagation with Residual Memory Compensation

Stochastic digital backpropagation (SDBP) is an extension of digital backpropagation (DBP) and is based on the maximum a posteriori principle. SDBP takes into account noise from the optical amplifiers in addition to handling deterministic linear and nonlinear impairments. The decisions in SDBP are taken on a symbol-by-symbol (SBS) basis, ignoring any residual memory, which may be present due to non-optimal processing in SDBP. In this paper, we extend SDBP to account for memory between symbols. In particular, two different methods are proposed: a Viterbi algorithm (VA) and a decision directed approach. Symbol error rate (SER) for memory-based SDBP is significantly lower than the previously proposed SBS-SDBP. For inline dispersion-managed links, the VA-SDBP has up to 10 and 14 times lower SER than DBP for QPSK and 16-QAM, respectively.Comment: 7 pages, accepted to publication in 'Journal of Lightwave Technology (JLT)