The fiber-optic microampere current sensor used two metal-coated single mode optical fibers to detect the current when it pass through the coated part which existing a thermal resistance effect.When the optical fiber experience temperature change,variation of the phase shift would be incurred by the change of refractive index and geometric structure of the fiber.Then we can observe the phase amplitude to know the input current.Besides we combine the all-fiber Michelson interferometer with the Faraday rotator mirror to build up a polarization-insensitive structure.Final using the phase-generated carrier technique(PGC) to stabilize demodulate the phase signal.

No description available.

This thesis concerns with the development of a dual-parameter sensor based on fiber Bragg grating (FBG) and a packaging design for high pressure sensing in harsh environment. This thesis starts by introducing a novel design of a partially coated FBG, using a metallic insert and a thermal curing epoxy. An analytical opto-mechanical model, based on couple mode theory, was developed and presented. The experimental and modelling result of the optical response of the partially coated FBG were compared and shown to be in excellent agreement. The experiments were executed on a custom-built fiber optic calibration station. The coated FBG sensor has a temperature sensitivity of 26.9 ± 0.3 pm/°C, which is 2.7 times higher than a bare fiber; and a force sensitivity of 0.104 nm/N, which is 13 times smaller than a bare fiber. The zero reference of the sensor has a drift of a maximum of 70 pm but the sensor is shown to settle within ±5 pm after 3 thermal cycles and 10 tensile loading cycles. A low profile packaging design is presented for a maximum pressure of 20.68 MPa (3000 psi) for harsh environment applications. A detailed study with FEM analysis revealed the optimal design for the package’s sleeve thickness is 0.5 mm. The temperature sensitivity is in close agreement with the unpackaged coated sensor with 10% difference. Compared to the modelling, the equivalent force sensitivity is 27% lower due to prototype dimensional uncertainties and modelling uncertainties with the material properties. The lack of pre-tension of the FBG sensor in the package also attributed to lower force sensitivity at pressure level lower than 4.13 MPa (600 psi).

Orientador: Cláudio Kitano / Banca: Mauro Henrique de Paula / Banca: Aparecido Augusto de Carvalho / Resumo: A interferometria a laser é uma técnica consolidada para a caracterização de atuadores piezoelétricos. No entanto, este método requer um alinhamento óptico preciso e uma operação meticulosa. Há um grande interesse no desenvolvimento de sistemas de medição de deslocamento e vibração usando sensores reflexivos em fibra óptica devido a sua inerente simplicidade, tamanho reduzido, largura de banda ampla, limite de detecção extremamente baixo e capacidade de realizar medições sem contato ou afetar o sistema a ser ensaiado. Neste trabalho apresenta-se um arranjo simples do sensor reflexivo para se atingir resolução sub-micrométrica, utilizando-se fibras e componentes ópticos de baixo custo e circuitos eletrônicos simples. O sistema é constituído por duas fibras ópticas adjacentes (uma transmissora e outra receptora) e com extremidades emparelhadas, posicionadas na frente de uma superfície reflexiva vibratória. A luz proveniente de uma fonte óptica (no caso um laser) é acoplada à fibra transmissora e parte dos raios refletidos pela superfície móvel é capturada pela fibra receptora, que conduz a luz para um fotodetector. A tensão de saída do fotodetector é função da distância entre as extremidades das fibras e a superfície reflexiva. Apresenta-se uma formulação teórica da função de intensidade óptica refletida no plano a uma distância qualquer, juntamente com comparações entre características experimentais e teóricas do sensor reflexivo. Finalmente, atuadores piezoelétricos flextensionais, projetados com o método de otimização topológica, são caracterizados experimentalmente através da medição de seus deslocamentos sub-micrométricos, utilizando o sensor reflexivo. As respostas em freqüência dos piezoatuadores flextensionais são levantadas e o fenômeno de erro de trajetória e linearidade são discutidos. / Abstract: The laser interferometer method is a well-established technique for the characterization of piezoelectric actuators. However, this method requires precise optical alignment and meticulous operation. There is great interest in developing displacement and vibration measurement systems using reflective fiber optic displacement sensors (RFODS) because of their inherent simplicity, small size, wide frequency range, extremely low displacement detection limit, and ability to perform measurements without contact or affecting the vibrating system. This work presents a simple arrangement of RFODS to achieve sub-micrometer resolution, using low-cost fibers and optical components, and simple electronic circuits. The system is composed of two adjacent transmitting and receiving fibers at one end, located in front of a reflecting vibrating surface. The transmitting fiber is connected to a laser source, and part of the reflected rays by the moving surface is captured by the receiving fiber, which is connected to a light detector. The output voltage is a function of the distance between probe and vibrating surface. A theoretical formulation of the reflected light intensity function at distal end plane is presented, together with comparisons of experimental and ideal RFODS characteristics. Finally, piezoelectric flextensional actuators (PFAs), designed with the topology optimization method, are experimentally characterized by the measurement of their sub micrometric displacements using a RFODS. The frequency responses of the PFAs are evaluated, and the tracking error phenomenon and linearity are discussed. / Mestre

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-20T13:25:52Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação-digital.pdf: 2703779 bytes, checksum: 932fadac81fdbfd0fee52b9e614ccf40 (MD5) / Made available in DSpace on 2016-07-20T13:25:52Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação-digital.pdf: 2703779 bytes, checksum: 932fadac81fdbfd0fee52b9e614ccf40 (MD5) Previous issue date: 2015-07-20 / Esta dissertação apresenta a construção e caracterização de um protótipo de cabeça sensora óptica para medição da corrosão em estruturas metálicas que têm o zinco como elemento de proteção. O elemento sensor consiste de uma fibra óptica com ponta metalizada com zinco. A fabricação da cabeça sensora envolve a clivagem, limpeza e deposição do metal. A caracterização foi realizada colocando o elemento sensor num sistema de medição óptica que mede o sinal óptico refletido pelo metal depositado na face da fibra. Foram estudados três métodos de deposição: térmica, por spray metálico e por sputtering. Porém, a deposição por sputtering foi a única que se mostrou ser mais adequada na construção do elemento sensor. Os resultados da medição pelo sistema proposto sugerem ser possível monitorar a corrosão do metal na ponta da fibra pela modulação do sinal óptico refletido. Desta forma, ao medir o tempo entre a intensidade da luz refletida máxima e mínima, foi possível calcular a taxa de corrosão do zinco. Isso sugere que as cabeças construídas, nos experimentos desta dissertação, têm um grande potencial para serem utilizadas num sistema óptico de monitoramento da corrosão em estruturas galvanizadas. / This dissertation presents the construction and characterization of a prototype optical sensor head for measuring corrosion on metal structures that have zinc as a protective element. The sensor element consists of an optical fiber with metalized face with zinc. The manufacture of the sensor head involves the cleavage, cleaning and metal deposition. Characterization was made by placing the sensor element in an optical measuring system that measures the optical signal reflected by the metal deposited on the face of the fiber. Three methods of deposition were studied, thermal, by metal spraying and sputtering. However, the sputtering deposition was the only one that was more appropriate in the construction of the sensor element. The measurement results by the proposed system suggest that it is possible to monitor metal corrosion on the tip of the fiber optic signal modulation reflected. Therefore, when measuring the time between intensity maximum and minimum reflected light, it was possible to calculate the zinc corrosion rate. This suggests that the heads built, in this dissertation, have great potential to be used in the optical system of monitoring corrosion in galvanized structures.

Submitted by Fabio Sobreira Campos da Costa (fabio.sobreira@ufpe.br) on 2016-07-20T15:27:06Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação-digital.pdf: 2703779 bytes, checksum: 932fadac81fdbfd0fee52b9e614ccf40 (MD5) / Made available in DSpace on 2016-07-20T15:27:06Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Dissertação-digital.pdf: 2703779 bytes, checksum: 932fadac81fdbfd0fee52b9e614ccf40 (MD5) Previous issue date: 2015-07-20 / Esta dissertação apresenta a construção e caracterização de um protótipo de cabeça sensora óptica para medição da corrosão em estruturas metálicas que têm o zinco como elemento de proteção. O elemento sensor consiste de uma fibra óptica com ponta metalizada com zinco. A fabricação da cabeça sensora envolve a clivagem, limpeza e deposição do metal. A caracterização foi realizada colocando o elemento sensor num sistema de medição óptica que mede o sinal óptico refletido pelo metal depositado na face da fibra. Foram estudados três métodos de deposição: térmica, por spray metálico e por sputtering. Porém, a deposição por sputtering foi a única que se mostrou ser mais adequada na construção do elemento sensor. Os resultados da medição pelo sistema proposto sugerem ser possível monitorar a corrosão do metal na ponta da fibra pela modulação do sinal óptico refletido. Desta forma, ao medir o tempo entre a intensidade da luz refletida máxima e mínima, foi possível calcular a taxa de corrosão do zinco. Isso sugere que as cabeças construídas, nos experimentos desta dissertação, têm um grande potencial para serem utilizadas num sistema óptico de monitoramento da corrosão em estruturas galvanizadas. / This dissertation presents the construction and characterization of a prototype optical sensor head for measuring corrosion on metal structures that have zinc as a protective element. The sensor element consists of an optical fiber with metalized face with zinc. The manufacture of the sensor head involves the cleavage, cleaning and metal deposition. Characterization was made by placing the sensor element in an optical measuring system that measures the optical signal reflected by the metal deposited on the face of the fiber. Three methods of deposition were studied, thermal, by metal spraying and sputtering. However, the sputtering deposition was the only one that was more appropriate in the construction of the sensor element. The measurement results by the proposed system suggest that it is possible to monitor metal corrosion on the tip of the fiber optic signal modulation reflected. Therefore, when measuring the time between intensity maximum and minimum reflected light, it was possible to calculate the zinc corrosion rate. This suggests that the heads built, in this dissertation, have great potential to be used in the optical system of monitoring corrosion in galvanized structures.

The financial requirements between fiber optic sensors and conventional sensors are gradually declining, which, despite many advatages and wide range of applicationas, has slowed down the demand for these sensors. With the demand for fiber optic sensors also grow the requirements for the parameters of these sensors. This thesis deals with distributed temperature fiber optic sensors. Non--linear phenomen in optical fibers, such as Raman scattering is used for measuring with these sensors. This scatterin was used to obtain information about temperature, which effected the optical cable under the test.

Recently, adding more lanes becomes less and less feasible, which is no longer an applicable solution for the traffic congestion problem due to the increment of vehicles. Using the existing infrastructure more efficiently with better traffic control and management is the realistic solution. An effective traffic management requires the use of monitoring technologies to extract traffic parameters that describe the characteristics of vehicles and their movement on the road. A three-dimension glass fiber-reinforced polymer packaged fiber Bragg grating sensor (3D GFRP-FBG) is introduced for the traffic monitoring system. The proposed sensor network was installed for validation at the Cold Weather Road Research Facility in Minnesota (MnROAD) facility of Minnesota Department of Transportation (MnDOT) in MN. A vehicle classification system based on the proposed sensor network has been validated. The vehicle classification system uses support vector machine (SVM), Neural Network (NN), and K-Nearest Neighbour (KNN) learning algorithms to classify vehicles into categories ranging from small vehicles to combination trucks. The field-testing results from real traffic show that the developed system can accurately estimate the vehicle classifications with 98.5 % of accuracy. Also, the proposed sensor network has been validated for low-speed and high-speed WIM measurements in flexible pavement. Field testing validated that the longitudinal component of the sensor has a measurement accuracy of 86.3% and 89.5% at 5 mph and 45 mph vehicle speed, respectively. A performed parametric study on the stability of the WIM system shows that the loading position is the most significant parameter affecting the WIM measurements accuracy compared to the vehicle speed and pavement temperature. Also the system shows the capability to estimate the location of the loading position to enhance the system accuracy.

No description available.

Optical fibers are getting significant considerations in the field of the sensors and sensing beyond its applications in optical communications. Because of several advantages, e.g., low profile of the sensors, immunity to electromagnetic noises, the ability of multiplexing, etc., the use of the fiber optic sensor is increasing in the field of physical, chemical, and biomedical sensing. In this study, we have developed two new fiber optic sensors based on fiber loop ringdown technique (FLRD) and have demonstrated their applications in the field of sensing. In the first part of this study, we report on the development of a high-sensitivity FLRD strain sensor. For the design of the strain sensor, the fiber loop was cut at the middle, and then the two fiber ends from broken fiber loop were cleaved and aligned carefully to couple the light from one end to another end. Any strain during the measurement changes the alignment of the fiber ends, consequently, the ringdown time changes. With this scheme, the FLRD strain sensor has shown the strain detection limit of 65 nanostrain, which is five times better than any FLRD strain sensors reported in the literature. Furthermore, The FLRD strain sensors were successfully embedded into prestressed concrete-beams.The FLRD strain sensor was able to monitor stress on a post-tensioned rod, as well as the load applied on the concrete-beam during the three-point loading test, thus exhibiting immense potential in structural health monitoring. For the chemical sensor, a new scheme of interrogation for a fiber optic surface plasmon sensor was developed with the use of the FLRD technique. A gold nanolayer was deposited on an uncladded fiber section, and the fiber section was integrated into the FLRD system as a sensor head. The gold layer facilitates for increased interaction of sample of interest, with the light pulse confined in the fiber waveguide. Moreover, with the affinity of the gold with specific biomolecules, the sensor has the potential for applications in biochemical sensing. In the experiment, the SP-FLRD sensor was used for refractive index sensing, and index detection limit of 4.6×10-5 RIU was achieved.