Metrologia óptica com fibra polimérica

Doutoramento em FísicaO presente trabalho teve por objectivo global o estudo e desenvolvimento de sensores baseados em fibra óptica polimérica. O crescimento da tecnologia polimérica nos últimos anos permitiu a introdução deste tipo de fibras ópticas na área das telecomunicações e no desenvolvimento de sensores. As vantagens associadas à metrologia óptica com fibra polimérica têm vindo a atrair as atenções da comunidade científica dado que permitem o desenvolvimento de sistemas de baixo-custo ou custo competitivo face às tecnologias convencionais. Dada a actualidade do tema proposto, descreve-se, numa primeira fase, a tecnologia em fibra óptica polimérica existente no mercado e o estado de arte de sensores em fibra óptica polimérica. Segue-se a descrição de dois tipos de sensores baseados em modulação de intensidade. Projectou-se um sensor extrínseco capaz de avaliar a quantidade de luz dispersa e absorvida por partículas suspensas num líquido. Foi efectuada a caracterização do sensor quanto à concentração de partículas suspensas, tamanho e reflectividade. O sensor foi testado no âmbito da monitorização ambiental, designadamente, na análise de turbidez em amostras de sedimentos recolhidos em áreas ardidas. O sistema desenvolvido foi comparado com um sistema comercial. Um sensor intrínseco, baseado no polimento lateral de fibra óptica polimérica, foi analisado analiticamente. O modelo teórico avalia o sensor em diferentes condições de macroencurvamento e de índice de refracção do meio envolvente. O modelo teórico foi validado positivamente através de resultados experimentais. Foi avaliada a sensibilidade à temperatura e os conhecimentos adquiridos foram aplicados no desenvolvimento de um sistema capaz de monitorizar a cura de diferentes materiais. É ainda apresentada uma técnica para melhorar a sensibilidade do sensor de curvatura através da aplicação de um revestimento na zona sensível. A dependência na curvatura da potência transmitida por uma fibra óptica polida lateralmente serviu de base ao desenvolvimento de uma joelheira e de uma cotoveleira instrumentada, capazes de avaliar quantitativamente o movimento articular. A necessidade de portabilidade levou ao desenvolvimento de um sistema sem fios para aquisição e transmissão de dados. Espera-se que os protótipos desenvolvidos venham a ter um impacto significativo em sistemas futuros aplicados à medicina física e reabilitação.The global aim of this thesis was the study and development of optical sensors based on plastic optical fibre. The recent advance of polymer technology allowed the introduction of this type of optical fibre in telecommunications and sensor design. The advantages of optical metrology with plastic fibre have attracted attention from the scientific community because it allows the development of low-cost or cost competitive systems compared with conventional technologies. Given the relevance of the topic, the current plastic optical fibre technology and the state of the art of plastic optical fibre optic sensors are described. Two types of intensity-based sensors are presented. An extrinsic sensor was designed in order to measure the amount of scattered and absorbed light by particles suspended in a liquid. The characterisation of the sensor was accomplished with respect to the concentration of the suspended particles, size and reflectivity. The sensor was tested in environmental monitoring, particularly, in the analysis of turbidity in sediment samples collected from burned areas and compared to a commercial system. An intrinsic sensor based on side-polished plastic optical fibre was analytically analysed. The theoretical model assesses the sensor performance in different conditions of curvature and refractive index of the surrounding media. The theoretical model has been positively validated by experiments. The sensitivity of the sensor to the temperature was also evaluated and the knowledge acquired was applied to the development of a pressure sensor and a system capable of monitoring the cure of different materials. A technique for improving the sensor sensitivity is also presented by the application of a coating on the sensitive area. The dependence of the transmitted power of a side-polished plastic optical fibre on the curvature was used in the development of a system for monitoring knee and elbow angle. These devices allowed the quantitative assessment of the human motion. The need of portability led to the introduction of a wireless data transmission system. It is expected that the developed prototypes will play an important role in future physical medicine and rehabilitation systems.POPH; FCT; FS

Low cost color assessment of turbid liquids using supervised learning data analysis – proof of concept

This work reports the development of a low cost in-line color sensor for turbid liquids based on the transmission and scattering phenomena of light from RGB and IR LED sources, gathering multidimensional data. Three different methodologies to discriminate color from the turbidity influence are presented as a proof of concept approach. They are based in regression models, expectation maximization Gaussian mixtures and artificial neural networks applied to labeled measurements. Each methodology presents advantages and disadvantages which will depend on the intended implementation. Regression models revealed to be best suited for standard or occasional measurements, the EM Gaussian mixture will perform better for well-known controlled range of colors and turbidities and the neural networks have easy implementation and potential suited for real-time IoT platforms.publishe

Inscription of narrow bandwidth bragg gratings in polymer optical fibers

We report on the production and characterization of narrow bandwidth fiber Bragg gratings (FBGs) in two spectral regions using polymer optical fibers (POFs). Narrow bandwidth FBGs are increasingly important for POF transmission systems, WDM technology and sensing applications. Long FBGs with resonance wavelength around 850 nm and 1550 nm were fabricated in several types of polymer optical fibers. The 3 dB FBG bandwidth varies from 0.22 nm down to 0.045 nm considering a Bragg grating length of 10 mm and 25 mm, respectively

UV inscription and pressure induced long-period gratings through 3D printed amplitude masks

In this work, we demonstrate for the first time the capability to inscribe long-period gratings (LPGs) with UV radiation using simple and low cost amplitude masks fabricated with a consumer grade 3D printer. The spectrum obtained for a grating with 690 µm period and 38 mm length presented good quality, showing sharp resonances (i.e., 3 dB bandwidth < 3 nm), low out-of-band loss (~0.2 dB), and dip losses up to 18 dB. Furthermore, the capability to select the resonance wavelength has been demonstrated using different amplitude mask periods. The customization of the masks makes it possible to fabricate gratings with complex structures. Additionally, the simplicity in 3D printing an amplitude mask solves the problem of the lack of amplitude masks on the market and avoids the use of high resolution motorized stages, as is the case of the point-by-point technique. Finally, the 3D printed masks were also used to induce LPGs using the mechanical pressing method. Due to the better resolution of these masks compared to ones described on the state of the art, we were able to induce gratings with higher quality, such as low out-of-band loss (0.6 dB), reduced spectral ripples, and narrow bandwidths (~3 nm).publishe

Acousto-optic effect in microstructured polymer fiber bragg gratings:simulation and experimental overview

A fine control of the microstructured polymer fiber Bragg grating spectrum properties, such as maximum reflected power and 3-dB bandwidth, through acousto-optic modulation is presented. For simulation purposes, the device is modelled as a single structure, comprising a silica horn and a fiber Bragg grating. For similar sized structures a good correlation between the numerical results and the experimental data is obtained, allowing the strain field to be completely characterized along the whole structure. It is also shown that the microstructured polymer fiber Bragg grating requires less effort from the piezoelectric actuator to produce modification in the grating spectrum when compared with a silica fiber Bragg grating. This technique has potential to be applied on tunable optical filters and tunable cavities for photonic applications

GÊNEROS ORAIS FORMAIS: O QUE É POSSÍVEL E NECESSÁRIO SER ENSINADO NO LIVRO DIDÁTICO DESTINADO A PESSOAS JOVENS, ADULTAS E IDOSAS?

What do textbooks propose when they present a set of strategies for working with formal oral genres in the classroom?This questioning guides this work that investigated the treatment with formal oral genres presented by a collection of textbooks directed to the education of Young, Adult and Elderly people. To achieve this goal we focus on the documentary approach(FLICK, 2009, LOPES e GALVÃO, 2001) to analyze the collection “É Bom Aprender” (PNLD, 2011), acquired by 16 (sixteen) municipalities of public education networks of Mata Norte Pernambucana. To discuss the investigated phenomenon, we submitted the collection to an interpretivist analysis, based on a qualitative approach (BORTONI-RICARDO, 2008).The results indicate the presence of proposals aimed at the use of formal oral, favorable to the understanding of dimensions related to social uses however, it is limited from the point of view of the space of reflection on the various discursive situations and on the approximations between the genres materialized in the oral and written modalities of the language. Faced with this scenario,we reinforce the importance that working with formal oral textual genres in EJAI classes is a primary task for the students' teaching-learning process, since it contributes to the acquisition of an effective social-linguistic development that, therefore, favors the consolidation of subjects' rights.O que propõem os livros didáticos quando apresentam um conjunto de estratégias para trabalhar os gêneros orais formais em sala de aula? Esse questionamento pauta este trabalho que investigou o trato com os gêneros orais formais apresentados por uma coleção de livros didáticos direcionados à educação de pessoas jovens, adultas e idosas. Para alcançar esse objetivo, tomamos como foco a abordagem documental (FLICK, 2009, LOPES e GALVÃO, 2001) para analisar a coleção “É Bom Aprender” (PNLD, 2011), adquirida por 16 (dezesseis) municípios de redes públicas de ensino da Mata Norte Pernambucana. Para a discutir o fenômeno investigado, submetemos a coleção a uma análise interpretativista, com base em uma abordagem qualitativa (BORTONI-RICARDO, 2008). Os resultados sinalizam para a presença de propostas, voltadas para o uso do oral formal, favoráveis à compreensão sobre dimensões relativas aos usos sociais. Contudo, são limitadas do ponto de vista do espaço da reflexão sobre as variadas situações discursivas e sobre as aproximações entre os gêneros materializados nas modalidades oral e escrita da língua. Frente a esse cenário, reforçamos a importância de que trabalhar com os gêneros textuais orais formais nas turmas de EJAI é uma tarefa primordial para o processo de ensino-aprendizagem dos/as educandos/as, uma vez que contribui para a ampliação das práticas linguísticas e sociais, com vista a favorecer a consolidação dos direitos dos sujeitos

ENTREVISTA EM MANUAIS DE EDUCAÇÃO DE JOVENS, ADULTOS E IDOSOS: UM GÊNERO TEXTUAL PARA ENSINAR A ORALIDADE

The general objective of this article was to investigate the didacticization of the interview in the textbook collection “EJA Moderna”, aimed at the Education of Young, Adult and Elderly People (EJAI); and specifically, to understand which strategies are proposed for the experience of textual genre in the school context. To achieve these objectives, we anchor our work on assumptions of orality studies, focusing on proposals for textbooks intended for EJAI. From a methodological point of view, we resorted to Document Analysis and Content Analysis and treated the data under a qualitative lens. According to the results, we observed that the investigated book provides reflections on the interview genre in several aspects. We found that the book mobilizes the pedagogical action of raising prior knowledge about the genre in question, which contributes to the possibility of planning the teaching of orality based on the knowledge of the students. Another interesting finding is the fact that the book deals with the compositional structure and the social function of the interview, paying attention to the social roles of the interlocutors and to the alternation of pairs of questions and answers. The study's conclusions point to the importance of the work in contributing to the teaching of interview production.Este artigo tomou como objetivo geral investigar a didatização da entrevista na coleção de livro didático “EJA Moderna”, destinada à Educação de pessoas Jovens, Adultas e Idosas (EJAI); e de modo específico, compreender quais estratégias são propostas para a vivência do gênero textual no contexto escolar. Para alcançar esses objetivos, ancoramos nosso trabalho em pressupostos de estudos da oralidade, com foco nas proposições de livros didáticos destinados à EJAI. Do ponto de vista metodológico, recorremos à Análise Documental e à Análise de Conteúdo e tratamos os dados sob uma lente qualitativa. De acordo com os resultados, observamos que o livro investigado propicia reflexões sobre o gênero entrevista em vários aspectos. Constatamos que o livro mobiliza a ação pedagógica de levantar conhecimentos prévios sobre o gênero em questão, o que contribui para a possibilidade de um planejamento de ensino da oralidade a partir dos conhecimentos dos(das) educandos(as).&nbsp; Outro achado interessante é o fato de o livro tratar sobre a estrutura composicional e a função social da entrevista, atentando para os papéis sociais dos interlocutores e para a alternância dos pares perguntas e respostas.&nbsp; As conclusões do estudo apontam para a importância de a obra contribuir para o ensino da produção da entrevista

Low-cost interrogation system for dynamic sensor applications using a resin based fiber Fabry Perot filter

In this paper it will be presented a prototype of a low-cost power interrogator for dynamic sensor applications. The proposed system is based on the edge filter technique, where the slope of an in-house resin based Fabry Perot (FP) filter is used to actively filter the power of a narrowband laser centred at the middle part of the FP slope region. The interrogator is composed of a laser source, circulator, photodetector, Arduino board and laptop. Tests have been performed in order to check the viability of the system. Finally, the measurement of a pulse wave signal has been performed by embedding the FP sensor in a 3D printed elastic membrane and reading the signal through the proposed interrogator

Strain Sensitivity Control of an In-Series Silica and Polymer FBG

This work reports on the use of an in-series silica and polymer fiber Bragg grating (FBG) to control the FBG strain sensitivities and enhance in the case of the polymer fiber Bragg grating (PFBG). Due to differences in the Young&rsquo;s Modulus of the fibers employed, the amount of strain is unequally distributed in each fiber section. By acting on the silica fiber length, it was possible to control the strain sensitivity of the two FBGs, allowing a polymer FBG strain sensitivity much higher than the one found in the elementary fiber to be obtained. The influence of the diameter of the polymer fiber on the strain sensitivities of the FBGs was also investigated. Results have shown that, besides the strain sensitivity control, an even greater improvement in the PFBG strain sensitivity can be achieved

Inscription of narrow bandwidth bragg gratings in polymer optical fibers

We report on the production and characterization of narrow bandwidth fiber Bragg gratings (FBGs) in two spectral regions using polymer optical fibers (POFs). Narrow bandwidth FBGs are increasingly important for POF transmission systems, WDM technology and sensing applications. Long FBGs with resonance wavelength around 850 nm and 1550 nm were fabricated in several types of polymer optical fibers. The 3 dB FBG bandwidth varies from 0.22 nm down to 0.045 nm considering a Bragg grating length of 10 mm and 25 mm, respectively