A configurable optical add-drop multiplexer (OADM) based on fiber Bragg gratings is reported. Dynamical selection of the add-drop or pass-through functionality is realized according to the control of an optical switch. OADM performance measurements in a 70-km, 3 x 2.5-Gb/s channel wavelength division multiplexing (WDM) network are reported. The wavelength tuning capacity for the OADM is studied.

O presente trabalho tem por objectivo o estudo dos diversos componentes optoelectrónicos que constituem uma rede fotónica, com vista ao aumento da flexibilidade, débito, conectividade e desempenho. Para tal, são analisados os blocos e funções essenciais que permitem a implementação de uma rede óptica transparente e multiplexada no comprimento de onda. Inicialmente, caracterizaram-se os diversos componentes optoelectrónicos envolvidos em redes ópticas multicomprimento de onda, tendo-se dado uma ênfase especial ao meio de transporte de informação, nomeadamente, às propriedades não lineares das fibras ópticas. Foi implementado laboratorialmente um demonstrador de um nó óptico de extracção e inserção de canais sintonizável, baseado numa rede de Bragg gravada em fibra óptica, tendo esta configuração de nó evoluído para um estágio de protótipo comercial. Foi, também, implementado um demonstrador de um nó óptico de cruzamento de canais, completamente reconfigurável baseado em componentes discretos disponíveis comercialmente, onde se demonstra uma arquitectura estritamente não bloqueante. Foram estudadas as diversas técnicas de conversão de comprimento de onda e implementado um módulo capaz de realizar conversão de comprimentos de onda, no domínio óptico e independente do ritmo e formato de modulação, que suporta ritmos de transmissão de 2.5 Gbit/s, baseado na modulação cruzada do ganho num amplificador óptico semicondutor reflectivo. Por fim, foi desenvolvida uma metodologia transparente de análise do desempenho em sistemas de comunicações ópticas utilizando amostragem assíncrona. Foi derivado um modelo para os histogramas assíncronos em função das características dos impulsos, tendo-se implementado um módulo de análise de qualidade de serviço de uma rede óptica.

With the rapid development of digital ecosystems, such as mobile applications towards goods/monetary transactions, a new paradigm of data transfer arises, which requires fast and reliable algorithms to generate random numbers. The statistical nature of speckle‐ based imaging creates an opportunity for these generators to arise as random number generators given the unpredictability and irreproducibility of such patterns. Hence, it is shown that the establishment of an experimental system is able to produce unique speckle patterns for remote cryptographic key storage and distribution, with a potential key rate generation of Gbs.

In this study, the implementation of an optical accelerometer unit based on fiber Bragg gratings, suitable to monitor structures with frequencies up to 45 Hz, is reported. The developed optical system was used to estimate the structure eigenfrequencies of a steel footbridge, with a total length of 300 m, over the Sao Pedro Creek, located at University of Aveiro Campus, in Portugal. The acceleration records measured with this solution are compared with those obtained by traditional commercial electronic devices, revealing a root-mean-square error of 2.53 x 10(-5) G.

We propose an optical fiber hydrostatic pressure sensor based on micro-cavities generated by the fiber fuse effect. The presented sensor is manufactured through the recycling of optical fiber destroyed by the fiber fuse effect, being, therefore, a cost-effective solution, when compared with other similar micro-cavity-based solutions. The developed sensor was characterized for pressures up to 20 kPa, showing a linear sensitivity coefficient of 0.47 +/- 0.03 nm . kPa(-1), for pressure values below 8 kPa. Furthermore, we propose a new theoretical model to describe the behavior of the microcavities embedded in optical fibers. This allows us to solve the discrepancies, already identified by other authors, between the experimental results and the ones attained with the flat mirrors Fabry-Perot model. By this way, we were able to describe the sensor response, within the full dynamic range.

This paper presents a structural health monitoring system for monitoring, with reduced visual impact, one historical building structural. The system is based on fiber Bragg gratings and comprises 19 displacement sensors and 5 temperature sensors. All the sensors were custom made according to the monitoring points' characteristics. The results obtained over the first year of monitoring are presented. The objective of this work is to gather data that will bring a deeper knowledge of how this structure behaves and to help planning the recovering interventions in this historical building.

Building-integrated photovoltaics (BIPV) offers a sustainable pathway by seamlessly incorporating PV cells into architectural elements like façades and windows. In this study, we investigate the potential of luminescent down-shifting solar concentrators in combination with a nanophotonic light-trapping scheme to improve the optical-guiding capabilities and thereby enhance the energy conversion efficiency. We propose a novel cost-effective method to fabricate the photonic structures via soft colloidal lithography negative templating of thin films of TiO2 nanoparticles, successfully scaling the production to 11x11 cm2 glass windows. Through simulations and optical-electrical characterization, we demonstrate substantial improvements in energy harvesting for different angles of solar irradiation. We found increases in power output ranging from 57% for angles of incidence below 45° to above 100% for 60° thanks to the nanostructured TiO2 nanoparticles coatings added to a bottom down-shifting layer. This shows that such integrated approach can enhance both the efficiency and aesthetic appeal of solar solutions in urban environments, advancing the design of energy-efficient, sustainable buildings. Our methodology ensures consistent solar energy capture all year-round, for the relevant range of sunlight incidence angles, while preserving the transparency and multifunctionality of building elements.