DSpace Repository :: Browsing by Author "Fierens, Pablo Ignacio"

Browsing by Author "Fierens, Pablo Ignacio"

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Analytical study of coherence in seeded modulation instability
(2016-09) Bonetti, Juan I.; Hernández, Santiago M.; Fierens, Pablo Ignacio; Grosz, Diego
"We derive analytical expressions for the coherence in the onset of modulation instability, in excellent agreement with thorough numerical simulations. As usual, we start by a linear perturbation analysis, where broadband noise is added to a cw pump; then, we investigate the effect of adding a deterministic seed to the cw pump, a case of singular interest as it is commonly encountered in parametric amplification schemes. Results for the dependence of coherence on parameters such as fiber type, pump power, propagated distance, and seed signal-to-noise ratio are presented. Finally, we show the importance of including higher-order linear and nonlinear dispersion when looking at longer-wavelength regions"
Anti-stokes Raman gain enabled by modulation instability in mid-IR waveguides
(2018-11) Sánchez, Alfredo D.; Fierens, Pablo Ignacio; Hernández, Santiago M.; Bonetti, Juan I.; Brambilla, Gilberto; Grosz, Diego
"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 CW 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."
Clogging transition of vibration-driven vehicles passing through constrictions
(2017-12) Patterson, Germán; Fierens, Pablo Ignacio; Sangiuliano Jimka, Federico; König, Pablo; Garcimartín, Ángel; Zuriguel, Iker; Pugnaloni, Luis Ariel; Parisi, Daniel
"We report experimental results on the competitive passage of elongated self-propelled vehicles rushing through a constriction. For the chosen experimental conditions, we observe the emergence of intermittencies similar to those reported previously for active matter passing through narrow doors. Noteworthy, we find that, when the number of individuals crowding in front of the bottleneck increases, there is a transition from an unclogged to a clogged state characterized by a lack of convergence of the mean clog duration as the measuring time increases. It is demonstrated that this transition—which was reported previously only for externally vibrated systems such as colloids or granulars—appears also for self-propelled agents. This suggests that the transition should also occur for the flow through constrictions of living agents (e.g., humans and sheep), an issue that has been elusive so far in experiments due to safety risks."
Conteo de personas
(2020-12-10) Fariña, Segundo; Rodríguez, Gastón; Fierens, Pablo Ignacio
"El objetivo del presente trabajo es el desarrollo un sistema de conteo de personas utilizando una cámara desde una vista cenital. Un caso de uso típico es el de un local comercial con la cámara registrando el acceso al mismo de manera que el sistema permite obtener estadísticas del flujo de clientes a lo largo de una jornada. En este sentido, el sistema no sólo cuenta la cantidad de personas en el área de interés, sino que también analiza la dirección de las mismas. Un requerimiento del sistema es que tenga un muy bajo costo, por lo que se dispone que las imágenes sean tomadas por una cámara webconvencional."
A direct method for the simultaneous estimation of self-steepening and the fractional Raman contribution in fiber optics
(2021-06) Linale, N.; Bonetti, Juan I.; Fierens, Pablo Ignacio; Hernández, Santiago M.; Grosz, Diego
"We propose an original, simple, and direct method for the simultaneous estimation of the selfsteepening 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 Schrödinger 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."
Dispersive waves in optical fibers with a zero-nonlinearity wavelength
(2021-08) Sparapani, Alexis; Linale, N.; Grosz, Diego; Bonetti, Juan I.; Fierens, Pablo Ignacio; Hernández, Santiago M.
"We present results on dispersive waves radiated by solitons in the context of fibers with arbitrary frequency-dependent nonlinearities. In particular, we focus on the effect of a zero-nonlinearity wavelength within the spectral region of interest."
Enhanced anti-stokes Raman gain in nonlinear waveguides
(2019) Sánchez, Alfredo D.; Hernández, Santiago M.; Bonetti, Juan I.; Grosz, Diego; Fierens, Pablo Ignacio
"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 antiStokes 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".
Estudio comparativo de métodos de sensado en radio cognitiva: sensado cooperativo de energía
(2016) Schwoyer, Germán; Fierens, Pablo Ignacio
"Este trabajo de tesis propone el estudio comparativo de varios métodos de sensado cooperativo del espectro empleados en Radio Cognitiva."
Estudio de la interoperabilidad entre distintos equipamientos DWDM
(2017) Sequeira, Pedro Ignacio; Fierens, Pablo Ignacio
"Este trabajo de especialización propone el estudio experimental de diversos aspectos relacionados con la compatibilidad a nivel funcional entre equipamientos de transmisión DWDM de distintas marcas."
Experimental investigation of noise-assisted information transmission and storage via stochastic resonance
(2010-05) Patterson, Germán; Goya, Andrés F.; Fierens, Pablo Ignacio; Ibáñez, Santiago Agustín; Grosz, Diego
"We present experimental results on the information transmission and storage via stochastic resonance in circuits designed and built around Schmitt triggers (STs). First, we investigate the performance of a transmission line comprised of five STs and show it to exhibit stochastic resonance. Each ST in the line is fed with white Gaussian noise, and the first ST is driven by a non-return-to-zero pseudo-random bit sequence with sub-threshold amplitude. Parameters such as bit error rate (Q-factor) are measured (calculated) and shown to exhibit a minimum (maximum) for an optimum amount of noise. Interestingly, we find that system performance degrades with the number of STs as if the system were linear and impaired only by additive Gaussian noise. We then propose and build a 1-bit storage device based on two STs in a loop configuration. We demonstrate that such a system is capable of storing one bit of information only in the presence of noise, and that there is a regime where the efficiency of such a device increases with increasing noise. Our results point to the feasibility of building 'blocks' that can transmit, store and eventually process information, whose performance is not only robust against noise, but can actually benefit from it. © 2010 Elsevier B.V. All rights reserved."
An extension of chaotic probability models to real-valued variables
(2008-07) Fierens, Pablo Ignacio
"Previous works have presented a frequentist interpretation of sets of measures as probabilistic models which have denominated chaotic models. Those models, however, dealt only with sets of probability measures on ﬁnite algebras, that is, probability measures which can be related to variables with a ﬁnite number of possible values. In this paper, an extension of chaotic models is proposed in order to deal with the more general case of real-valued variables."
Fusion of magnetic and WiFi fingerprints for indoor positioning
(2018) Grisales Campeón, Juan Pablo; López, Sebastián; de Jesús Meleán, Sergio R.; Moldovan, Horatiu; Parisi, Daniel; Fierens, Pablo Ignacio
"WiFi received signal strength (RSS) and magnetic field intensity are common measures for indoor localization because they are readily available on most mobile devices. There is a vast literature on smartphone positioning using RSS and it has been widely implemented in real-world scenarios in the last two decades. There is much work done on localization aided by magnetic field measurements. We have recently evaluated the accuracy of RSS-based positioning applying state-of-the-art algorithms to measurements in a well-controlled experimental setup. In this paper, we extend this work to assess the accuracy improvements achievable by fusing WiFi and magnetic field information. We show that accuracy improvements of up to 30% are possible."
A generic model for the study of supercontinuum generation in graphene-covered nanowires
(2022-01) Linale, N.; Fierens, Pablo Ignacio; Vermeulen, N.; Grosz, Diego
"We study supercontinuum (SC) generation in graphene-covered nanowires based on a generic model that correctly accounts for the evolution of the photon number under Kerr and two-photon absorption processes, and the influence of graphene is treated within the framework of saturable photoexcited-carrier refraction. We discuss the role of the various effects on the generation of SC by a thorough analysis of short-pulse propagation in two different kinds of graphene-covered nanowires, one made of silicon nitride and the other made of silicon. Finally, we discuss the effect of stacking graphene layers as a means to enhance SC generation with pulse powers compatible with those in integrated optical devices."
A geometrical view of scalar modulation instability in optical fibers
(2017) Hernández, Santiago M.; Fierens, Pablo Ignacio; Sánchez, Alfredo D.; Grosz, Diego; Bonetti, Juan I.
"Full models of scalar modulation instability (MI) in optical fibers available in the literature usually involve complex formulations. In this paper, we present a novel approach to the analysis of MI in optical fibers by means of a simple geometrical description in the power versus frequency plane. This formulation allows us to relate the shape of the MI gain to any arbitrary dispersion profile of the medium, thus providing a simple insight. As a result, we derive a straightforward explanation of the nontrivial dependence of the cutoff power on high-order dispersion and explicitly derive the power that maximizes the gain. Our approach puts forth a tool to synthesize a desired MI gain with the potential application to a number of parametric-amplification and supercontinuum-generation devices whose initialstage dynamics rely upon MI."
Guest editorial special issue on embedded systems
(2020-02) De Micco, Luciana; Vargas, Fabian; Fierens, Pablo Ignacio
"La temática de sistemas embebidos (SE) tiene una enorme relevancia debido al gran número de aplicaciones en muy diversas áreas. En los últimos años ha habido un interés especial animado por las áreas emergentes de la Internet de las Cosas (IoT, según la sigla en inglés) y la Industria 4.0."
A higher-order perturbation analysis of the nonlinear Schrödinger equation
(2019-06) Bonetti, Juan I.; Hernández, Santiago M.; Fierens, Pablo Ignacio; Grosz, Diego
"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."
Indoor positioning based on RSSI of WiFi signals: how accurate can it be?
(2019-02-20) Grisales Campeón, Juan Pablo; López, Sebastián; de Jesús Meleán, Sergio R.; Parisi, Daniel; Fierens, Pablo Ignacio; Moldovan, Herman
"There is abundant literature on positioning systems based on WiFi signals. Most of the systems with off-the-shelf hardware use RSSI measurements. In this paper, we try to determine the highest achievable accuracy of such systems. Instead of resorting to a theoretical analysis, e.g., Cram´er-Rao or Ziv-Zakai bounds, we apply state-of-the-art localization algorithms to measurements in a well-controlled experimental setup. We conclude that an accuracy of less than 1 meter seems unrealistic."
Indoor positioning system
(2019-11-29) Li Puma, Juan Francisco; Rodríguez Nicastro, Julián; de Rochebouët, Diego; Fierens, Pablo Ignacio
"GPS and location services have been a breakthrough in recent history and have become a necessary part of our daily lives, but they haven't yet reached the point where we can be located inside buildings. This would be really useful, with multiple applications such as localization in big buildings, location-based advertising, location-assisted games, locationaware social networks, etc. For this reason, there has been research on the eld to solve this problem and many possible approaches have been found. This project presents a starting point for one of these solutions using WiFi ngerprinting. The project consists of an API and two mobile applications that consume it, one for admins and another for users. The admin app is used to gather samples needed for WiFi ngerprinting in an onlne stage and the user app is used to locate users based on WiFi scans on an online stage. This solution is then tested and the results are presented."
A literature review on embedded systems
(2020-02) De Micco, Luciana; Vargas, Fabian; Fierens, Pablo Ignacio
"Embedded system design is crucial for the development of industry, technology, and science, and it is an area that has significantly grown in recent years throughout Latin America, both in academia and in industry. Embedded System (ES) refers to electronic equipment with a computing core which, unlike a personal computer, is designed to meet a specific function and is usually optimized to satisfy strict requirements of processing time, reliability, power consumption, size, and cost. With the advancement of research on the domains of Internet of Things (IoT), Computing Edge (CE) and Cloud Computing (CC) and their endless application possibilities, ESs have gained new roles and assumed unquestionable importance in our daily lives. In this article, we make a brief review of the relevant literature in the area of embedded systems in the Latin America region during recent years."
Measuring self-steepening with the photon-conserving nonlinear Schrödinger equation
(2020-08-15) Linale, N.; Fierens, Pablo Ignacio; Bonetti, Juan I.; Sánchez, Alfredo D.; Hernández, Santiago M.; Grosz, Diego
"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."

Browsing by Author "Fierens, Pablo Ignacio"

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