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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.

This thesis is composed of two distinct parts. The first part of this work addresses the problem of critical ignition behind a decaying shock wave in the context of cellular detonations. Low-pressure (4.1 kPa) shock tube experiments were performed in a thin rectangular channel using the highly-unstable mixture of CH4 + 2O2 and the weakly-unstable mixture of 2H2 + O2 + 7Ar, with Schlieren visualization of the flow field. The dynamics of the lead shock in a detonation cell was reconstructed from measurements of the lead shock position and curvature. The post-shock state and the expansion rate along the path of a Lagrangian particle crossing the lead shock at any given point in the cell cycle were evaluated with the shock jump and shock change equations. The chemical evolution behind the shock was then integrated using a detailed chemistry model. Quenching of the post-shock reaction zone was found within the first half of the detonation cell for both mixtures, with quenching occurring earlier in the highly unstable mixture. Simplified models derived from 1-step and 2-step chemistry models very accurately predict the quenching of the post-shock reactions and the evolution of the ignition delay through the cell. The second part describes the assembly and characterization of a fibre-optic probe hydrophone (FOPH) for the measurement of shock waves associated with blast-induced neuro-trauma. Compared to traditional polyvinylidene difluoride (PVDF) hydrophones, the assembled FOPH has a higher bandwidth and smaller active diameter, which are comparable to the characteristic time and thickness of shock waves associated with blast-induced neuro-trauma. However, the sensitivity of FOPHs are substantially lower than traditional hydrophones. We assemble a FOPH and provide detailed calculations and measurements of its sensitivity (0.66 mV/MPa) , noise floor, and spatial resolution. The 150 MHz bandwidth, limited by the photodetector, is sufficient for resolving shock waves with over-pressures of up to 174 kPa with 3 measurement points. Experimental measurements of the system noise gives a floor of 260 Pa/√Hz . A detailed noise analysis finds that the system is limited by photodetector noise (215 Pa/√Hz), which is 4x the fundamental shot noise limit, closely followed by a laser noise of 150 Pa/√Hz. We conclude that the system noise floor is insufficient for resolved measurements of the post-shock pressure in the range associated with blast-induced neuro-trauma. From our noise analysis, we quantify the sensitivity enhancement required for resolving this regime, and we conclude that sensitivity-enhancing fibre-coatings could provide a sufficient increase in sensitivity.

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This thesis concerns various aspects of the durability offibre optic sensors embedded in composite. Since repair orreplacement of embedded sensors is not generally possible, thefunctional reliability of embedded sensors is one of the mostimportant prerequisites for successful use. The main researchobjective was to investigate the interaction between the sensorand the composite, and how this is affecting the mechanical andoptical sensor response. Fibre optic sensors embedded incomposite structures induce local stress concentrations whenthe composite is subjected to mechanical loads andenvironmental changes such as temperature and moisture. Acomplex transfer of stresses through the interfaces between theembedded sensor and the composite occurs and can result inlarge local stresses in the composite and a significant changein the response of the embedded sensor. These stressconcentrations make the interfaces susceptible todebonding. The sensor performance was studied experimentally andnumerically. Some basic results were generated for the EFPI andBragg grating sensors. The phase-strain response was determinedduring static and fatigue loading. The results showed that thesensors were more reliable in compression than in tensilestatic and fatigue loading. Generally, the sensor reliabilityduring loading was significantly improved for the Bragg gratingsensors over that of the EFPI sensor, as an effect of thesensor geometry. This was also demonstrated in theinvestigations on impacts. Impacts do not necessarily result indamage in the composite, but might cause debonding or otherfailure modes in the sensor area. Large, local stressconcentrations occur at several positions in the EFPI sensor,which pointed out that this sensor type was not suitable forembedded applications. The shift in focus from the sensor concept based on the EFPIsensor to that based on the Bragg grating sensor manifesteditself in several studies. The calculated deformation fieldaround an embedded optical fibre was verified in experimentsusing a high-resolution moiré interferometric technique.Furthermore, the improvement in the coating technology wasverified. A significant higher interfacial strength wasobtained with the silane-treated glass surface. The resultsindicated that at least a twofold improvement of the shearstrength was obtained. To simultaneously measure the in-plane strain components andthe temperature change, embedded Bragg grating sensors werearranged in a rosette configuration. The relationship betweenthe optical response from each sensor and the strains in thelaminate was numerically and analytically established. Damage lead to stress redistribution in the sensor region,which may influence the output from the embedded Bragg gratingsensor. The effect was numerically evaluated for interfacialdamage, and was compared to that of a sensor with undamagedinterface. The results showed that debonding might have asignificant influence, in particular for combined thermal andmechanical loading. <b>Keywords</b>: composites, fibre optic sensor, embedded, EFPIsensor, Bragg grating sensor, durability, fatigue, impact,strain measurement, interface, stress analysis

<p>This thesis concerns various aspects of the durability offibre optic sensors embedded in composite. Since repair orreplacement of embedded sensors is not generally possible, thefunctional reliability of embedded sensors is one of the mostimportant prerequisites for successful use. The main researchobjective was to investigate the interaction between the sensorand the composite, and how this is affecting the mechanical andoptical sensor response. Fibre optic sensors embedded incomposite structures induce local stress concentrations whenthe composite is subjected to mechanical loads andenvironmental changes such as temperature and moisture. Acomplex transfer of stresses through the interfaces between theembedded sensor and the composite occurs and can result inlarge local stresses in the composite and a significant changein the response of the embedded sensor. These stressconcentrations make the interfaces susceptible todebonding.</p><p>The sensor performance was studied experimentally andnumerically. Some basic results were generated for the EFPI andBragg grating sensors. The phase-strain response was determinedduring static and fatigue loading. The results showed that thesensors were more reliable in compression than in tensilestatic and fatigue loading. Generally, the sensor reliabilityduring loading was significantly improved for the Bragg gratingsensors over that of the EFPI sensor, as an effect of thesensor geometry. This was also demonstrated in theinvestigations on impacts. Impacts do not necessarily result indamage in the composite, but might cause debonding or otherfailure modes in the sensor area. Large, local stressconcentrations occur at several positions in the EFPI sensor,which pointed out that this sensor type was not suitable forembedded applications.</p><p>The shift in focus from the sensor concept based on the EFPIsensor to that based on the Bragg grating sensor manifesteditself in several studies. The calculated deformation fieldaround an embedded optical fibre was verified in experimentsusing a high-resolution moiré interferometric technique.Furthermore, the improvement in the coating technology wasverified. A significant higher interfacial strength wasobtained with the silane-treated glass surface. The resultsindicated that at least a twofold improvement of the shearstrength was obtained.</p><p>To simultaneously measure the in-plane strain components andthe temperature change, embedded Bragg grating sensors werearranged in a rosette configuration. The relationship betweenthe optical response from each sensor and the strains in thelaminate was numerically and analytically established.</p><p>Damage lead to stress redistribution in the sensor region,which may influence the output from the embedded Bragg gratingsensor. The effect was numerically evaluated for interfacialdamage, and was compared to that of a sensor with undamagedinterface. The results showed that debonding might have asignificant influence, in particular for combined thermal andmechanical loading.</p><p><b>Keywords</b>: composites, fibre optic sensor, embedded, EFPIsensor, Bragg grating sensor, durability, fatigue, impact,strain measurement, interface, stress analysis</p>

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.