1,720,970 research outputs found
Full Spectrum b-Modulation of Time-Limited Signals Using Linear Programming
No full textWe present the first method for the joint modulation of the continuous and the discrete nonlinear Fourier spectrum of finite duration signals.Accepted Author ManuscriptTeam Sander Wahl
Shortening Solitons for Fiber-Optic Transmission
No full textSolitons are stable localized pulses that do not disperse in optical fiber. When several solitons interact, they form a multi-soliton. Various fiber-optic communication systems based on multi-solitons have been investigated, but their spectral efficiencies are not competitive. One issue with using multi-solitons for communications is that their effective duration can vary widely with the number of interacting solitons. In this paper, we therefore introduce the concept of soliton shortening. In soliton shortening, a dispersive part is added to the nonlinear spectrum of a multi-soliton that reduces the pulse to a fixed finite duration, without changing the characteristics of the solitonic part. As a proof of concept, soliton shortening is shown to increase the spectral efficiency of a 2-soliton on-off keying system by 40%.Accepted Author ManuscriptTeam Sander Wahl
Discrete Darboux based fast inverse nonlinear Fourier transform algorithm for multi-solitons
No full textA fast algorithm for constructing multi-solitons with linear complexity in the number of samples and eigenvalues is introduced. The algorithm is shown to be significantly faster than the conventional Darboux transform in a numerical example, with acceptable error.Accepted Author ManuscriptTeam Raf Van de PlasTeam Sander Wahl
Analytic Interpolation and the Non-linear Fourier Transform
No full textThe non-linear Fourier transform may be considered an extension of Fourier analysis to non-linear problems. It has applications in many different scientific and engineering disciplines, for instance as a solution to the non-linear Schrödinger equation which describes how electro-magnetic waves travel through ideal non-linear media. Hence, the non-linear Fourier transform is fundamental for communication schemes that take optical fiber non-linearities into account. Wahls et al. proposed an algorithm for a fast inverse non-linear Fourier transform based around a discretization of the non-linear Schrödinger equation. But one of the steps in the algorithm — known as synthesis — only had heuristic solutions. However, the problem closely resembles a Nevanlinna-Pick interpolation with degree constraint, a problem known to have a guaranteed solution. Indeed, synthesis is a limit case of Nevanlinna-Pick interpolation with degree constraint on the boundary of the region of analyticity. Although there are solvers to the boundary Nevanlinna-Pick interpolation with degree constraint available in the literature, they do not scale to the numerical difficulty or size required, and are based around simplifying assumptions that do not hold for synthesis.In this thesis I propose two different numerical continuation solvers for synthesis. The methods have lower computational complexity than other guaranteed solvers by using fast linear Fourier transforms to perform polynomial operations. Moreover, the convergence speed of the algorithms is improved by approaching the solution in a novel trajectory. However, the solvers only offer a quicker convergence rate than the heuristic methods for very difficult problems, and may not be effective for real-time applications, as the high-demands in error precision required means a very high computational cost. This seems to be a limitation of the theory, as the high computational cost is a consequence of the large number of iterations required even when the cost of each iteration is low.Mechanical Engineering | Systems and Contro
Theoretical analysis of maximum transmit power in a <i>b</i>-modulator
No full textThe optimal transmit power in various nonlinear Fourier transform-based transmission systems has been observed to decrease with the signal duration when bandwidth is fixed. A new theoretical explanation for this behavior is provided for a specific b-modulator and validated in simulations.Accepted Author ManuscriptTeam Sander Wahl
NFDMLab: Simulating nonlinear frequency division multiplexing in Python
No full textFiber-optic transmission based on nonlinear frequency division multiplexing (NFDM) has received much attention in recent years. We introduce NFDMLab, an open source software package for simulating NFDM transmissions written in the Python language.Accepted Author ManuscriptTeam Sander Wahl
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Nonlinear Fourier transform algorithm using a higher order exponential integrator
No full textWe present a nonlinear Fourier transform algorithm whose accuracy, at a comparable runtime and for moderate step sizes, is orders of magnitude better than that of the classical Boffetta-Osborne method.Accepted Author ManuscriptTeam Sander WahlsTeam Raf Van de Pla
- …
