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We propose an original, simple, and direct method for the simultaneous estimation of the self-steepening parameter and the fractional Raman contribution in fiber optics. Our proposal is based on the dependence of the modulation instability gain on both parameters, as obtained from a linear stability analysis of the newly introduced photon-conserving generalized nonlinear Schrodinger equation (pcGNLSE), and requires only the CW or quasi-CW pumping of the waveguide under test and a few direct spectral measurements. Further, we demonstrate the feasibility of the estimation procedure by means of detailed simulations for typical waveguide parameters in relevant spectral ranges. Last, we discuss the range of applicability of the proposed method and compare its results, advantages, and disadvantages with a recently introduced method based on short-pulse dynamics.

We have recently introduced a new modeling equation for the propagation of pulses in optical waveguides, the photon-conserving Nonlinear Schrodinger Equation (pcNLSE) which, unlike the canonical NL...

We propose an original, simple, and direct method to measure self-steepening (SS) in nonlinear waveguides. Our proposal is based on results derived from the recently introduced photon-conserving nonlinear Schrödinger equation (NLSE) and relies on the time shift experienced by soliton-like pulses due to SS upon propagation. In particular, a direct measurement of this time shift allows for a precise estimation of the SS parameter. Furthermore, we show that such an approach cannot be tackled by resorting to the NLSE. The proposed method is validated through numerical simulations, in excellent agreement with the analytical model, and results are presented for relevant spectral regions in the near infrared, the telecommunication band, and the mid infrared, and for realistic parameters of available laser sources and waveguides. Finally, we demonstrate the robustness of the proposed scheme against deviations expected in real-life experimental conditions, such as pulse shape, pulse peak power, pulsewidth, and/or higher-order linear and nonlinear dispersion. Fil: Linale, Nicolás Martín. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comision Nacional de Energia Atomica. Gerencia D/area Invest y Aplicaciones No Nucleares. Gerencia de Des. Tec. y Proyectos Especiales. Departamento de Ingenieria En Telecomunicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Fierens, Pablo Ignacio. Instituto Tecnológico de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Bonetti, Juan Ignacio. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comision Nacional de Energia Atomica. Gerencia D/area Invest y Aplicaciones No Nucleares. Gerencia de Des. Tec. y Proyectos Especiales. Departamento de Ingenieria En Telecomunicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Sánchez, Alfredo Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comision Nacional de Energia Atomica. Gerencia D/area Invest y Aplicaciones No Nucleares. Gerencia de Des. Tec. y Proyectos Especiales. Departamento de Ingenieria En Telecomunicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina Fil: Hernandez, Santiago Martin. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Universidad Nacional de Cuyo; Argentina Fil: Grosz, Diego Fernando. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Comision Nacional de Energia Atomica. Gerencia D/area Invest y Aplicaciones No Nucleares. Gerencia de Des. Tec. y Proyectos Especiales. Departamento de Ingenieria En Telecomunicaciones; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina

A well-known and thoroughly studied phenomenon in nonlinear wave propagation is that of modulation instability (MI). MI is usually approached as a perturbation to a pump, and its analysis is based on preserving only terms which are linear on the perturbation, discarding those of higher order. In this sense, the linear MI analysis is relevant to the understanding of the onset of many other nonlinear phenomena, such as supercontinuum generation, but it has limitations as it can only be applied to the propagation of the perturbation over short distances. In this work, we propose approximations to the propagation of a perturbation, consisting of additive white noise, that go beyond the linear modulation instability analysis, and show them to be in excellent agreement with numerical simulations and experimental measurements. Fil: Bonetti, Juan Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Hernandez, Santiago Martin. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Fierens, Pablo Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Tecnológico de Buenos Aires; Argentina Fil: Grosz, Diego Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina

The Generalized Nonlinear Schrodinger Equation (GNLSE) finds several applications, especially in describing pulse propagation in nonlinear fiber optics. A well-known and thoroughly studied phenomenon in nonlinear wave propagation is that of modulation instability (MI). MI is approached as a weak perturbation to a pump and the analysis is based on preserving those terms linear on the perturbation and disregarding higher-order terms. In this sense, the linear MI analysis is relevant to the understanding of the onset of many other nonlinear phenomena, but its application is limited to the evolution of the perturbation over short distances. In this work, we propose quasi-analytical approximations to the propagation of a perturbation consisting of additive white noise that go beyond the linear modulation instability analysis. Moreover, we show these approximations to be in excellent agreement with numerical simulations and experimental measurements.

We show that, under certain conditions, modulation instability in nonlinear waveguides gives rise to the usual double-sideband spectral structure, but with a Raman gain profile. This process is enabled by the energy transfer from a strong laser pump to both Stokes and anti-Stokes sidebands in a pseudo-parametric fashion. We believe this striking behavior to be of particular value in the area of Raman-based sensors which rely on sensitive measurements of the anti-Stokes component.

In this Letter, we present, for the first time, to the best of our knowledge, the modulation instability (MI) gain spectrum of waveguides with an arbitrary frequency-dependent nonlinear coefficient ensuring strict energy and photon-number conservation of the parametric process. This is achieved by starting from a linear stability analysis of the recently introduced photon-conserving nonlinear Schrödinger equation. The derived MI gain is shown to predict some unique features, such as a nonzero gain extending beyond a zero-nonlinearity wavelength and a complex structure of the MI gain spectrum. Analytical results are shown to be in excellent agreement with numerical simulations.

Pulse propagation in nonlinear waveguides is most frequently modeled by resorting to the generalized nonlinear Schrödinger equation (GNLSE). In recent times, exciting new materials with peculiar nonlinear properties, such as negative nonlinear coefficients and a zero-nonlinearity wavelength, have been demonstrated. Unfortunately, the GNLSE may lead to unphysical results in these cases since, in general, it does not preserve the number of photons and, in the presence of a negative nonlinearity, predicts a blue shift due to Raman scattering. In this paper, we put forth a modified GNLSE that can be used to model the propagation in media with an arbitrary, even negative, nonlinear coefficient. This novel photon-conserving GNLSE (pcGNLSE) ensures preservation of the photon number and can be solved by the same tried and trusted numerical algorithms used for the standard GNLSE. Finally, we compare results for soliton dynamics in fibers with different nonlinear coefficients obtained with the pcGNLSE and the GNLSE.

We revisit modulation instability in optical fibers, including all relevant effects, such as higher-order dispersion terms, self-steepening, and the Raman response. Our analysis allows us to calculate the spectral evolution of a small perturbation to a continuous pump, and thus obtain an analytical expression for the small-signal spectral dynamics, showing excellent agreement with numerical simulations. We apply the expression for the spectral evolution to the case of white Gaussian noise and calculate some relevant metrics of the resulting signal, such as its coherence and signal-to-noise ratio. These calculations might shed some light on the nonlinear phenomena of supercontinuum generation.

We propose a novel and simple method for estimating the fractional Raman contribution, fR, based on an analysis of a full model of modulation instability (MI) in waveguides. An analytical expression relating fR to the MI peak gain beyond the cutoff power is explicitly derived, allowing for an accurate estimation of fR from a single measurement of the Raman gain spectrum. Fil: Sánchez, Alfredo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Linale, Nicolás Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Bonetti, Juan Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Hernandez, S. M.. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Fierens, Pablo Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Instituto Tecnológico de Buenos Aires; Argentina Fil: Brambilla, G.. University of Southampton; Reino Unido Fil: Grosz, Diego Fernando. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

The inclusion of self-steepening in the linear stability analysis of modulation instability (MI) leads to a power cutoff above which the MI gain vanishes. Under these conditions, MI in mid-IR waveguides is shown to give rise to the usual double-sideband spectrum, but with Raman-shaped sidelobes. This results from the energy transfer of a continuous-wave laser simultaneously to both Stokes and anti-Stokes bands in pseudo-parametric fashion. As such, the anti-Stokes gain matches completely the Stokes profile over the entire gain bandwidth. This remarkable behavior, not expected from an unexcited medium, is shown not to follow from a conventional four-wave mixing interaction between the pump and the Stokes band. We believe this observation to be of relevance in the area of Raman-based sensors, which, in several instances, rely on monitoring small power variations of the anti-Stokes spectral component.