Publicação
Hybrid sensors based on hollow core optical fibers
| Resumo: | In this work, the development of several hybrid optical fiber sensors based on hollow core fibers was aimed. The sensing structures enhanced multiple interferometers in a single sensing cavity, which were monitored towards simultaneous measurement of multiple parameters. Firstly, a study was carried out over the different interferometers that arise in a section of silica capillary tube (SCT) spliced between two single mode fibers (SMF). The Fabry-Perot interferometer (FPI), antiresonant guidance (AR) and the Mach-Zehnder interferometer (MZI) were explored. The first hybrid sensor fabricated was based on the SMF-SCT-SMF structure with access channels instilled on the fiber with two methods that allowed the fabrication of an up to two-access channel sensor. The sensor was characterized to pressure and temperature in a reflection scheme, enhancing an FPI and AR for a 2 mm sensor. Different sensitivities were attained for both interferometers, thus the simultaneous measurement of the parameters under study was proposed. A different explored configuration was the balloon-like fiber sensor with the SMF-SCT-SMF configuration. This structure was bent in a balloon shape with the SCT in the top-center position. The 1.2 cm SCT length sensor was studied in a transmission configuration with a 4 cm balloon-length, enhancing AR guidance as well as an MZI, which was enforced by the bending derived from the balloon structure. Simultaneous measurement of displacement and temperature was achieved for the MZI and AR. Additionally, an access channel was instilled in the SCT, and the balloon-like sensor was sensitive to pressure for both components. Finally, a configuration based on a SMF-hollow square core fiber-SCT was developed and studied in a reflection scheme. A 439 μm long hollow square core fiber was able to excite three distinct FP cavities in a single sensing element. The different modes were monitored towards several physical parameters by using the Fourier band-pass filter method. The sensor was able to achieve a multiparameter simultaneous measurement of pressure, temperature, and curvature, for a certain fixed rotation. All the studied inline sensors all revealed potential hybrid application for simultaneous measurement of several parameters while constituting a single sensing head. The sensors possess reduced dimensions, high robustness, and simple configurations, making them great contenders for their implementation on several applications. |
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| Autores principais: | Santos, João Pedro Fidalgo |
| Assunto: | Hollow core fiber Optical fiber sensors Hybrid sensors Silica capillary tube Access channel Hollow square core fiber Antiresonance Fabry-Perot interference Mach-Zehnder interference |
| Ano: | 2022 |
| País: | Portugal |
| Tipo de documento: | dissertação de mestrado |
| Tipo de acesso: | acesso aberto |
| Instituição associada: | Universidade de Aveiro |
| Idioma: | inglês |
| Origem: | RIA - Repositório Institucional da Universidade de Aveiro |
| Resumo: | In this work, the development of several hybrid optical fiber sensors based on hollow core fibers was aimed. The sensing structures enhanced multiple interferometers in a single sensing cavity, which were monitored towards simultaneous measurement of multiple parameters. Firstly, a study was carried out over the different interferometers that arise in a section of silica capillary tube (SCT) spliced between two single mode fibers (SMF). The Fabry-Perot interferometer (FPI), antiresonant guidance (AR) and the Mach-Zehnder interferometer (MZI) were explored. The first hybrid sensor fabricated was based on the SMF-SCT-SMF structure with access channels instilled on the fiber with two methods that allowed the fabrication of an up to two-access channel sensor. The sensor was characterized to pressure and temperature in a reflection scheme, enhancing an FPI and AR for a 2 mm sensor. Different sensitivities were attained for both interferometers, thus the simultaneous measurement of the parameters under study was proposed. A different explored configuration was the balloon-like fiber sensor with the SMF-SCT-SMF configuration. This structure was bent in a balloon shape with the SCT in the top-center position. The 1.2 cm SCT length sensor was studied in a transmission configuration with a 4 cm balloon-length, enhancing AR guidance as well as an MZI, which was enforced by the bending derived from the balloon structure. Simultaneous measurement of displacement and temperature was achieved for the MZI and AR. Additionally, an access channel was instilled in the SCT, and the balloon-like sensor was sensitive to pressure for both components. Finally, a configuration based on a SMF-hollow square core fiber-SCT was developed and studied in a reflection scheme. A 439 μm long hollow square core fiber was able to excite three distinct FP cavities in a single sensing element. The different modes were monitored towards several physical parameters by using the Fourier band-pass filter method. The sensor was able to achieve a multiparameter simultaneous measurement of pressure, temperature, and curvature, for a certain fixed rotation. All the studied inline sensors all revealed potential hybrid application for simultaneous measurement of several parameters while constituting a single sensing head. The sensors possess reduced dimensions, high robustness, and simple configurations, making them great contenders for their implementation on several applications. |
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