Fiber Optic Refractive Index Distributed Multi-Sensors by Scattering-Level Multiplexing With MgO Nanoparticle-Doped Fibers

© 2020 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] In this work, we present the architecture of a multiplexed refractive index (RI) sensing system based on the interrogation of Rayleigh backscattering. The RI sensors are fabricated by fiber wet-etching of a high-scattering MgO nanoparticle-doped fiber, without the need for a reflector or plasmonic element. Interrogation is performed by means of optical backscatter reflectometry(OBR), which allows a detection with a millimeter-level spatial resolution. Multiplexing consists of a simultaneous scan of multiple fibers, achieved by means of scattering-level multiplexing (SLMux) concept, which uses the backscattered power level in each location as a diversity element. The sensors fabricated have sensitivity in the order of 0.473-0.568 nm/RIU (in one sensing point) and have been simultaneously detected together with a distributed temperature sensing element for multi-parameter measurement. An experimental setup has been prepared to demonstrate the capability of each sensing region to operate without cross-talk, while operating multi-fiber detection.This work was supported in part by the ORAU Programme at Nazarbayev University (LIFESTART and FOSTHER Grants), in part by the Agence Nationale de la Recherche (ANR) Project NanoSlim under Grant ANR-17-17-CE08-0002, in part by the National Natural Science Foundation for Excellent Youth Foundation of China under Grant 61722505, in part by the Key Program of Guangdong Natural Science Foundation under Grant 2018B030311006, and in part by The Spanish Ministry of Economy and Competitiveness under Grant DIMENSION TEC2017 88029-R. The associate editor coordinating the review of this article and approving it for publication was Prof. Marco Petrovich.Ayupova, T.; Shaimerdenova, M.; Korganbayev, S.; Sypabekova, M.; Bekmurzayeva, A.; Blanc, W.; Sales Maicas, S.... (2020). Fiber Optic Refractive Index Distributed Multi-Sensors by Scattering-Level Multiplexing With MgO Nanoparticle-Doped Fibers. IEEE Sensors Journal. 20(5):2504-2510. https://doi.org/10.1109/JSEN.2019.2953231S2504251020

Distributed fiber optics strain sensors: from long to short distance

Developed for more than forty years, optical fibers have features that make them particularly attractive for making sensors. One of the strengths of these sensors is that they can measure different physical parameters in a distributed manner over a wide range of lengths (from a few cm up to tens of kilometers) with a spatial resolution ranging from millimeters to meters. In this article, we are particularly interested in distributed fiber sensors, mainly based on light scattering processes, for measuring strain variations. This review concerns both applications requiring long lengths of fiber in a geological context, as well as those using length less than one meter for the medical sector. While distributed fiber optics sensors have already shown their great potential for long-range applications, short-range applications are a niche sector emerging in the last few years

Desenvolvimento e otimização de sensores em fibra ótica produzidos por laser de femtosegundo

In this work, optical fibre sensors were developed and optimized using a pulsed femtosecond laser. In addition to the inherent advantages of using femtosecond pulses, by emitting radiation in the NIR band, it was possible to modify the refractive index inside dielectric materials, namely silica and polymer optical fibres. Prior to the manufacturing of optical structures, a theoretical study was carried out on the peculiarities of writing-systems based on femtosecond lasers, as well as on the most common devices inscribed in optical fibres, namely Bragg gratings, long period gratings, and Fabry-Pérot interferometers. After assembling femtosecond NIR laser system, Bragg gratings, long period gratings, Fabry-Pérot interferometers, and interferometers based on the optical Vernier effect were manufactured using the direct-writing and phase mask methods. Using the micromachining setup, different structures were created in already existing optical fibre sensors, namely channels in hollow Fabry-Pérot cavities and laser etching around Bragg gratings inscribed in polymers optical fibres. The spectral responses of all devices were extensively characterized to, mainly, variations of temperature and strain, revealing unique sensitivity values, especially for the interferometers based on the optical Vernier effect (> 1 nm/°C and 0.1 nm/µε for temperature and strain, respectively). To demystify the thermal stability of fibre Bragg gratings, a theoretical and experimental study was carried out where several Bragg gratings were inscribed by different techniques, involving different lasers as well as silica and polymer optical fibres. The experimental results corroborated the theoretical predictions, where it was concluded that the gratings inscribed by the point-to-point method using a femtosecond laser have a greater thermal stability and lifetime, even when subjected to longer and higher temperature regimes. Finally, a bridge was stablished between the fundamental research developed during the manufacture of the elementary optical fibre sensors, and possible applications. Five different sensor concepts were demonstrated and tested, capable of detecting variations in magnetic fields, fluids refractive index, temperature, strain and humidity. As results, astonishing sensitivity values were attained, and several cross-sensitivity problems were mitigated, thus establishing the foundations for the development of new prototypes for the future.Neste trabalho foram desenvolvidos e otimizados sensores em fibra ótica através de um laser pulsado de femtosegundo. Para além das vantagens inerentes de usar pulsos da ordem do femtosegundo, ao emitir radiação na banda do infravermelho foi possível modificar o índice de refração no interior de materiais dielétricos, nomeadamente fibras óticas de sílica e polímero. Antes de proceder ao fabrico das estruturas óticas, foi realizado um estudo teórico sobre as peculiaridades dos sistemas de escrita baseados em lasers de femtosegundo, bem como sobre os principais dispositivos inscritos em fibra ótica, nomeadamente redes de Bragg, redes de período longo, e interferómetros de Fabry-Pérot. Após montado o sistema laser NIR de femtosegundo, através de inscrição direta e por máscara de fase foram fabricadas redes de Bragg, redes de período longo, interferómetros de Fabry-Pérot, e interferómetros baseados no efeito ótico de Vernier. Com a montagem de micromaquinação, diferentes estruturas foram criadas em sensores já existentes, nomeadamente buracos em cavidades Fabry-Pérot e remoção de material ao redor de redes de Bragg. As respostas espetrais de todos os dispositivos foram extensivamente caracterizadas, nomeadamente a variações de temperatura e tensão, revelando elevados valores de sensibilidades, especialmente para os interferómetros baseados no efeito ótico de Vernier (> 1 nm/°C e 0.1 nm/µε para temeprature e tensão, respetivamente). Para desmistificar a estabilidade térmica de redes de Bragg em fibra ótica, foi feito um estudo teórico e experimental onde várias redes de Bragg foram gravadas por diferentes técnicas, envolvendo diferentes lasers e fibras óticas de sílica e polímero. Os resultados experimentais corroboraram as previsões teóricas, onde se concluiu que as redes gravadas pelo método de ponto-a-ponto usando um laser de femtosegundo detêm uma maior estabilidade térmica e tempo de vida, mesmo quando submetidas a regimes longos de altas temperaturas. Por fim, foi feita a ponte entre a investigação fundamental desenvolvida durante o fabrico de dispositivos elementares em fibras óticas e possíveis aplicações. Foram demonstrados e testados cinco conceitos diferentes de sensores, capazes de detetar variações de campos magnéticos, índice de refração de fluídos, temperatura, tensão e humidade. Foram atingidos valores de sensibilidade surpreendentes, bem como mitigados problemas de sensibilidade cruzada, tendo sido assim estabelecidas as fundações para o desenvolvimento de novos protótipos para o futuro.Programa Doutoral em Engenharia Físic

Performance Analysis of Scattering-Level Multiplexing (SLMux) in Distributed Fiber-Optic Backscatter Reflectometry Physical Sensors

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