Caracterização da sensibilidade de fibras de cristal fotônico à pressão e temperatura para aplicações em sensoriamento

• Autor(a) principal: Oliveira, Rafael Euzebio Pereira de
• Data de Publicação: 2010
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações do Mackenzie
• Texto Completo: http://dspace.mackenzie.br/handle/10899/24423
• topic: fibras micro-estruturadas; fibras de cristal fotônico; sensores a fibra óptica; sensores de pressão; sensores de temperatura; microstructured fibers; photonic crystal fibers; optical fiber sensing; pressure sensors; temperature sensors; CNPQ::ENGENHARIAS::ENGENHARIA ELETRICA

In this dissertation the transmission properties of photonic crystal fibers are assessed under the influence of pressure and temperature for sensing applications. A review is given of the light propagation in conventional optical fibers and the effects of pressure and temperature on the refractive index of silica are studied. Photonic crystals in 1 and 2 dimensions are also studied. Then, microstructured fibers and photonic crystal fibers are addressed and their guidance properties and general applications are shown. A review is made of temperature and pressure sensors based on conventional fibers, Bragg gratings and microstructured and photonic crystal fibers described in the literature. Finally, results are shown and discussed of the experiments with the application of pressure on a hollow-core photonic crystal fiber, for which high-order bandgaps, in the visible spectral region, were identified and characterized for the first time. These bandgaps are shown to be pressure sensitive. Applying external hydrostatic pressure over the fiber, optical transmission variations of a few dB were observed for pressures of hundreds of kgf/cm², while when the fiber holes were internally pressurized a similar variation was achieved for units of kgf/cm². The response of light polarization, and hence of the fiber birefringence, to internal pressure was also analyzed.. In the other part of the experimental work, the temperature-induced bandgap spectral shift of photonic bandgap fibers was characterized. The response of a hollow-core fiber, a hybrid fiber and an all-solid fiber was characterized with bandgap shifts of up to 36 pm/°C in straight fibers. For the all-solid fiber the influence of bending over the bandgaps was characterized, as well as temperature-induced bandgaps shifts under these conditions. For a straight fiber, a simple model for the bandgap shift calculation is presented and showed good agreement with the experimental results. Closing the work, the conclusions are presented.