Purpose – In this work, the paper aims to demonstrate the feasibility of plastic optical fiber (POF) based accelerometers for the structural health monitoring (SHM) of civil engineering structures based on measurements of their dynamic response, namely to estimate natural frequencies. These sensors use POFs, combining the advantages of the optical technology with the robustness of this particular kind of fiber. The POF sensor output is directly compared with the signal from an electrical sensor, demonstrating the potential use of such sensors in structural monitoring applications. Design/methodology/approach – Within this work, the paper demonstrates the feasibility of using a low-cost acceleration system based on a POF accelerometer on the dynamic monitoring of a civil engineering structure, aiming its natural frequency evaluation, which is a primary parameter to be used in SHM methods and numerical models calibration. Findings – A low-cost POF-based accelerometer was used in the characterization of a civil engineering structural component, located in a building at the University of Aveiro Campus, being used to estimate its natural frequency with a relative error of 0.36 percent, comparatively to the value estimated recurring to a calibrated electronic sensor. Originality/value – Optical fiber sensors take advantage of the fibers properties, such as immunity to electromagnetic interference and electrical isolation. They are very attractive for use in hostile environments, like submerse environments or flammable atmospheres where electrical currents might pose a hazard. The advantages of POF itself should also be considered, like resistance to hash environments, robustness, flexibility, low-cost interrogation units and high numeric aperture (lower cost components). The paper demonstrates the feasibility of using a low-cost acceleration system based on a POF accelerometer on the dynamic monitoring of a civil engineering structure, aiming its natural frequency evaluation.

In this paper we propose the application of plastic optical fiber to monitor the concrete curing process. The proposed method is based in the scattering of the propagated optical signal in grooves imposed to the fiber. By monitoring the intensity of the transmitted light signal, along time, we can determine the cement setting rate along all the curing period. The obtained results show that the system has enough sensitivity to analyze a curing period of 28 days, where the received optical power is 5% of the initial value.

Nowadays, fiber to the Home/Curb/Building/Cabinet (FTTx) services that interconnect homes with a standard glass optical fiber cables to the core/access optical networks have brought the optical fiber at the doorsteps of our homes. However, the last few miles in home access network is still based on the limited bandwidth electronic component which supports by the cooper wires e.g. Cat-5, 6. The rapid growth of personal smart/mobile electronic devices with new developments such as video on demand, High Definition (HD) and three-Dimension (3D) television (TV), cloud computing, video conferences, etc. has been proposed new challenges for the next generation high bandwidth demand required for subscribers in home access network. In order to meet the more demanding expectations of the end user with new developments, it is necessary to improve the physical infrastructure of the existing in home networks in order to obtain the best ratio between quality of service and price of implementation. Plastic optical fibers (POFs) are point out as a promising transmission medium for short-range communication in compare to the “classic” single/multimode glass optical fibers and current cooper wire technology developments. The main advantages of POF are its easy to install, easy splicing and the possibility of using low cost optical transceivers, capability of being robust, and immunity to electromagnetic noise interference. However, the benefits of large-core POFs come at the expense of a less bandwidth and a higher attenuation than silica-based solution. The main objective of this doctoral dissertation is to explore the possibilities and develop low cost, short reach, high data rate POF-links for in home networks applications. This thesis investigates the use of multilevel modulation in particular, pulse amplitude modulation (PAM in combination of the receiver equalizer in order to overcome the bandwidth limitations of the graded index POFs. The possibility of the using multiple channels over a single fiber to increase the capacity of POF systems using commercially available multimode components is also analyzed in this dissertation. Moreover, a low cost Digitised radio signal over plastic fiber system is proposed and evaluated to deliver digital baseband data for wireline and wireless users in home access network. The deployment will be specified in terms of performance, maximum rates and any degradation that might appear in the network. Furthermore, the possibilities of the microstructured fibers in telecommunication application will be studied with main emphasis on their structural design. The photonic crystal fibers made of different highly nonlinear materials with different structures are optimized to achieve ultra-flat dispersion, high nonlinearity and low confinement loss over a broad range of wavelengths in the perspective of their usage in telecommunication applications.

This work reports de development and testing of a low cost plastic optical fiber liquid level sensor for operation within highly flammable or other hazardous environments, such in oil piping or fuel tanks. The sensor consists on a vertical fiber, with engraved grooves, that will be sequentially fulfill when the liquid rises, resulting in an increase of the transmitted optical power. A variation of 2.60% in the transmitted optical power intensity was obtained per measured point. Moreover, the sensor sensitivity and resolution can be tailored accordingly to the application.

In this paper, we report the development and experimental implementation of a low-cost, compact, intensity-encoded accelerometer based on polymer optical fibers (POF). The proposed accelerometer sensor element relies on the misalignment between two POFs, being the external acceleration encoded in the optical signal intensity. The accelerometer performance was optimized by simulation, resulting in a coupling efficiency and modulation index values of 0.38 and 1.78, respectively. The implemented device has a sensitivity of 33.5 +/- 0.1 mV/g and a resonant frequency of 51.44 +/- 0.1 Hz, obtained for a signal to noise ratio of 20 dB. This value for the resonant frequency is suitable for applications in several fields, such as structural health monitoring of civil engineering structures.

In this work we demonstrate the monitoring of the concrete curing process using a sensing system based on plastic optical fiber. The proposed sensor is based on an unjacketed plastic optical fiber with equally spaced grooves along the core. These grooves on the fiber, depending on the substance surrounding the fiber, enhance the scattering of the propagated optical signal. The transmitted optical power can be used to estimate the water content along the curing period.

Desde os tempos remotos, a luz tem sido utilizada como meio de comunicação, como, por exemplo, através de sinais de fumaça e sinalização de faróis. Esse método de comunicação, conhecido como Comunicação por Luz Visı́vel (VLC, do inglês Visible Light Communication), utiliza a parte visı́vel do espectro eletromagnético. A VLC tem ganhado popularidade com a disseminação das lâmpadas de LED, uma vez que é possı́vel utilizar a infraestrutura luminosa existente para estabelecer comunicação de dados. As lâmpadas de LED são uma escolha excelente para a VLC devido às suas caracterı́sticas vantajosas, tais como alta eficiência energética, confiabilidade, intensidade luminosa elevada e longa vida útil. Elas são especialmente adequadas para a comunicação, devido à sua ampla largura de banda e capacidade de modulação. Com o avanço da tecnologia, a VLC pode alcançar altas taxas de transmissão, da ordem de Gb/s, desde que o transmissor e o receptor estejam em linha de visada direta ou dentro do campo de visão do receptor. Uma alternativa para aprimorar o campo de visão do fotodetector é o uso de fibra óptica de plástico fluorescente vermelha como antena óptica, operando na faixa de 635 nm. Essa abordagem proporcionou um ganho de aproximadamente 28 dB no fotodiodo em relação à fonte luminosa, com uma abertura angular de 90o em relação ao receptor.

Este trabalho de conclusão de Curso consiste no desenvolvimento de fontes ópticas amarelas rápidas para enlaces com fibras ópticas poliméricas de base PMMA. A tecnologia de POFs (Fibras Ópticas Plásticas) possui como características a relativa simplicidade, flexibilidade, baixo custo e facilidade nas conexões ópticas e manipulações em geral, além de exibir praticamente todas as vantagens inerentes às fibras ópticas convencionais (sílica). Desta forma as POFs são convenientes para enlaces e redes de curtas distâncias, inclusive para a interligação de dispositivos em um ambiente sujeito a elevados níveis de interferências eletromagnéticas tais como computadores e periféricos, chips, placas de circuitos impressos, Redes Automotivas, Redes Industriais, Redes em Aeronaves entre outros. A síntese deste trabalho consiste basicamente em realizar a conversão rápida de comprimento de onda do espectro verde (520 nm) para o amarelo (560-570 nm) utilizando para isto Fibras Ópticas Poliméricas Fluorescentes (FPOFs) de base em poliestireno dopado. O interesse nestas fontes se deve a três razões: As POFs SI e DSI baseadas em Poli-Metil-Metacrilato (PMMA) exibem atenuação mínima em 560-570 nm, a ausência de LEDs e LDs de uso prático na referida faixa espectral amarela e a possibilidade de acrescentar ao menos mais um canal WDM sobre tais POFs de base PMMA. Como na referida faixa espectral, não existem disponíveis fontes semicondutoras apropriadas visando comunicações, este trabalho utilizou LEDs (Light Emitting Diode) verdes (520 nm) de alta potência como bomba (pump) com acoplamento óptico otimizado de forma a aumentar a eficiência efetiva da luz fluorescente amarela gerada em POFs (Fibras Ópticas Plásticas) fluorescentes/cintilantes e então acoplada na POF do enlace. O trabalho também contempla o desenvolvimento de acionadores (drivers) de corrente baseado em um transistor rápido visando os LEDs verdes de bombeio

Este trabalho tem como objetivo demonstrar um sistema de transmissão utilizando mutliplexação Discrete Multitone (DMT) para melhorar a eficiência espectral e aumentar a taxa de transmissão em enlaces de curta distância utilizando fibras óticas poliméricas. Assim, foi desenvolvido um esquema de multiplexação DMT modificado, com intuito de mitigar os efeitos dispersivos do canal (POF). Para demonstrar a eficiência do algorı́tmo de multiplexação foi utilizado um enlace de 20 m de fibra ótica de plástico de polimetilmetacrilato de índice degrau e quatro fontes ópticas de baixo custo, feitas para iluminação, com largura de banda analógica da ordem de 20 MHz. Uma dessas fontes foi desenvolvida no Laboratório de Comunicações Óticas (LACOP) da Universidade Federal Fluminense (UFF). Os resultados experimentais demonstraram uma eficiência espectral de 6.39bits/s/Hz para uma taxa de erro de bit (BER) alvo de 10 −3 oferecendo grande potencial, assim como a fonte óptica desenvolvida, para a implementação de um sistema de multiplexação por divisão de comprimentos de onda

Agradecimentos: This work was supported in part by National Funds through the FCT-Fundacao para a Ciencia e Tecnologia under Project PEst-OE/EEI/LA0008/2013 and scholarships (SFRH/BD/88472/2012 and SFRH/BPD/78205/2011), and in part by FINEP under Project 0112039300. The development of mPOF structure 1 was financed by the Wroclaw Research Centre EIT+