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Li, Kuo. "A novel method of Fiber Bragg Grating (FBG) strain modulation and its application in FBG accelerometers." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/76108/4/Kuo_Li_Thesis.pdf.
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This thesis has systemically investigated the possibility of improving one type of optical fiber sensors by using a novel mechanism. Many parameters of the sensor have been improved, and one outcome of this innovation is that civil structures, such as bridges and high-rise buildings, may be operated more safely and used longer.
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Xu, Xingyuan. "Improving the performance of FBG sensing system." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20070110.144936/index.html.
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Sethuraman, Gopakumar. "Fiber Bragg Grating (FBG) Based Chemical Sensor." VCU Scholars Compass, 2008. http://scholarscompass.vcu.edu/etd/1575.
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In this work, reagentless fiber optic-based chemical sensors for water quality testing were fabricated by coating fiber Bragg gratings with the glassy polymer cellulose acetate. With this polymeric matrix capable of localizing or concentrating chemical constituents within its structure, immersion of the coated grating in various chemical solutions causes the rigid polymer to expand and mechanically strain the glass fiber. The corresponding changes in the periodicity of the grating subsequently result in altered Bragg-reflected responses. A high-resolution tunable fiber ring laser interrogator is used to obtain room temperature reflectance spectrograms from two fiber gratings at 1550 nm and 1540 nm wavelengths. Rapidly swept measurements of the full spectral shapes yield real-time chemical detection and identification. With deionized water as a reference, wavelength shifts in the reflectivity transition edge from –82 pm to +43 pm and changes in response bandwidth from –27 pm to +42 pm are used to identify uniquely a diverse selection of chemical analytes.
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Abeywickrema, Haburugala Vithanage Ujitha A. "Behavior Of Linearly Polarized (LP) Modes in Fibers Containing Bragg Gratings in the Wide Temperature Range." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1313801169.
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Yeo, Jackson Teck Leong. "Application of FBG-based sensors in built environment." Thesis, City University London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440691.
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Lopes, Pedro José Ramos. "Aplicação de sensores FBG em modelos para injeção." Master's thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12548.
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Mestrado em Engenharia MecânicaCom o interesse crescente em analisar detalhadamente o comportamento do material fundido no processo de moldação por injeção, procedeu-se à aplicação de sensores de Bragg em fibra ótica (FBG) para medir temperaturas no interior do molde. Ainda hoje é uma incógnita precisar o comportamento do material polimérico no momento da injeção, principalmente a distribuição de temperaturas no perfil da frente de enchimento. Para cumprir o objetivo da dissertação foram gravadas 12 redes de Bragg em 4 fibras óticas distintas com o objetivo de criar uma malha 2D no interior da placa fixa do molde, a 3 mm do plano de partição. As redes foram gravadas de forma estratégica a coincidir com a superfície moldante que está em contacto com as peças que são injetadas. Para que as redes de Bragg ficassem operacionais, foram necessárias algumas etapas. A rede de Bragg é inscrita no núcleo da fibra ótica através de um método de gravação por laser. Com o intuito de conhecer o comportamento térmico de cada sensor de Bragg às variações de temperatura, procedeu-se a um ensaio de caracterização térmica em ambiente controlado. De seguida, foram instaladas no molde de injeção plástica as fibras óticas com os sensores e sequentemente elaborados alguns ensaios de injeção, cada um com aproximadamente 40 ciclos de moldação. Os resultados das experiências foram muitos semelhantes, e indicam que os sensores detetaram valores máximos de temperatura próximos dos 57 °C. Em cada ciclo de moldação as variações registadas nos sensores eram praticamente constantes e aproximadamente 3 ou 2 °C, conforme o sensor em causa. Antes dos ensaios no molde de injeção, foi realizada uma simulação numérica no software Autodesk Moldflow Synergy 2012. Esta serviu para prever os comportamentos térmicos do ciclo de moldação e também para determinar os valores de alguns dos parâmetros de operação na máquina de injeção. Esta tecnologia baseada em redes de Bragg é única, pois permite a disposição de inúmeros sensores de temperatura ao longo de uma fibra ótica, ocupando assim um volume muito reduzido. Estas vantagens aliadas à excelente resolução na aquisição de dados e à rápida resposta a impulsos térmicos fazem dos sensores FBG uma alternativa a ser tida em conta para futuros trabalhos relacionados com aplicações térmicas.
With the growing interest in thoroughly analyzing the behavior of the melted material in the process of injection molding, Fiber Bragg Gratings (FBG) were applied to measure temperatures in the mold interior. Still today it’s unknown to precise the polymeric material behavior in the fill time, especially the temperature distribution in the front flow profile. To fulfill the purpose of the dissertation12 Bragg gratings were recorded in 4 different optical fibers with the purpose of creating a two-dimensional mesh in the injection mold’s interior, 3 mm apart from the parting line. The gratings were inscribed in a strategic way to be placed over the molding surface which is in contact with the test specimens that are being injected. For the Bragg gratings become operational, several steps were required. The Bragg grating is written in the fiber’s core throughout a method using laser. An experience of thermal characterization in a controlled environment was mandatory to obtain the thermal behavior of each Bragg sensor. Then, the optical fibers with the gratings were inserted in the injection mold molding and sequent were made a few injection tests, each one with approximately 40 molding cycles. The results from the experiments were very similar and indicate that the sensors detect maximum values of temperature circa 57 °C. In each molding cycle the temperature variations were practically constant and were about 2 or 3 °C, depending on the sensor in use. Before the molding tests, a numeric simulation was made using software Autodesk Moldflow Synergy 2012. This was made to preview the thermal cycle behaviors and also to determinate the values of some particular input operational parameters for the injection molding machine. This technology based on Brag gratings is unique, because it allows the provision of numerous temperature sensors along a single optical fiber, thus occupying a very small volume. These advantages combined with the excellent resolution in the data acquisition and the quick response to thermal impulses make the FBG sensors an alternative to be taken in good advice for future investigations or tasks applied to the thermal field.
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Jacobsson, Fredrik. "DPSK modulation format for optical communication using FBG demodulator." Thesis, Linköping University, Department of Science and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2307.
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The task of the project was to evaluate a differential phase shift keying demodulation technique by replacing a Mach-Zehnder interferometer receiver with an optical filter (Fiber Bragg Grating). Computer simulations were made with single optical transmission, multi channel systems and transmission with combined angle/intensity modulated optical signals. The simulations showed good results at both 10 and 40 Gbit/s. Laboratory experiments were made at 10 Gbit/s to verify the simulation results. It was found that the demodulation technique worked, but not with satisfactory experimental results. The work was performed at Eindhoven University of Technology, Holland, within the framework of the STOLAS project at the department of Electro-optical communication.
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Deng, Fodan. "Corrosion Risk Assessment System For Coated Pipeline System." Diss., North Dakota State University, 2018. https://hdl.handle.net/10365/31713.
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Steel is widely used as building material for large-scale structures, such as oil and gas pipelines, due to its high strength-to-weight ratio. However, corrosion attack has been long recognized as one of the major reasons of steel pipeline degradation and brings great threat to safety in normal operation of structure. To mitigate the corrosion attacks, coatings are generally applied to protect steel pipelines against corrosion and improve durability of the associated structures for longer service life. Although have higher corrosion resistance, coated pipelines will still get corroded in a long run, as coatings may subject to damages such as cracks. Cracks on coatings could lower the effectiveness of protection for associated structures. Timely updates of up-to-date corrosion rate, corrosion location, and coating conditions to the pipeline risk management model and prompt repairs on these damaged coatings would significantly improve the reliability of protected structures against deterioration and failure. In this study, a corrosion risk analysis system is developed to detect and locate the corrosion induced coating cracks on coated steel using embedded fiber Bragg grating (FBG) sensors. The coatings investigated include high velocity oxygen fuel (HVOF) thermal sprayed Al-Bronze coating, wire arc sprayed Al-Zn coating, and soft coating. Theoretical models of corrosion risk assessment system were carried out followed by systematic laboratory experiments, which shows that the developed system can quantitatively detect corrosion rate, corrosion propagations, and accurately locate the cracks initialized in the coating in real time. This real-time corrosion information can be integrated into pipeline risk management model to optimize the corrosion related risk analysis for resource allocation. To place the sensing units of the system in the most needed locations along the huge pipeline systems for an effective corrosion risk assessment, an example case study is conducted in this study to show how to locate the most critical sensor placement locations along the pipeline using worst case oil and gas discharge analysis. Further applications of the developed system can be integrated with pipeline management system for better maintenance resource allocations.USDOT-PHMSA
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Lindley, Emma. "Multicore fibre Bragg gratings for astronomy." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/16682.
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Astrophotonics is the discipline of applying photonic technology in instrumentation to address problems in astronomy and astrophysics. Photonic devices known as fibre Bragg gratings (FBGs) can be used as highly selective filters for removal of unwanted light prior to dispersion in a spectrograph. It has been shown that FBGs are well suited to the problem of removing atmospheric molecular emission lines from ground-based near- infrared observations. This thesis describes the development of a new generation of FBGs for this purpose, inscribed within multi-core fibres (MCFs) which contain multiple single- mode cores within one cladding. A new component, the polished capillary tube (PCT), was modelled, fabricated and tested; results showed that this was an effective device for improving the uniformity of gratings within MCFs. Following this a protocol for temperature tuning of gratings relative to one another was developed and tested. Finally, this thesis describes the development of a new instrument for inscribing gratings in fibres. When MCF technology reaches maturity, they will be used in astronomical instruments for atmospheric suppression, and will also have applications wherever photonics is used.
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Perazzini, Matteo. "Evaluation of FBG strain sensor reliability through analytical, numerical and experimental results." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22947/.
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The fiber Bragg grating (FBG) sensor is one of the most suitable sensors for structural health monitoring (SHM) of aircraft structures. In principle, the FBG, with adequate sampling and signal processing techniques, is usually more accurate than classical electrical resistive strain gauge. However, since the most common installation method is surface bonding, some significative differences between the strain in the host structure and the one experienced by the fiber may be observed.
The aim of this work is the evaluation of the fiber Bragg grating optical fiber sensor reliability for strain detection in non-uniform strain conditions. A FBG sensor is surface bonded on a rectangular specimen with a centered hole under tensile loading. A multi device method for the strain detection is created with the use of optical fiber, strain gauge and DIC technologies at the same time. In addition, based on microscopic observations, a 3D finite element model of the bonded optical fiber is created to simulate the behavior of the test specimen and to have an insight into the strain transfer between the host material and the optical fiber core. Lastly, being the test specimen a well-known case in literature, the strain is also computed with closed-form expressions. All the experimental, numerical, and analytical results are then compared.
Taking into account the possible sources of error, the comparison shows coherence between the different results. The optical fiber strain sensor reliability is verified through the multiple device method which represents the starting point for future research activities.
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Petermann, Ann Britt [Verfasser]. "Optische Sensorsysteme auf Polymerbasis : neuartige FBG- und WGM-Strukturen / Ann Britt Petermann." Hannover : Technische Informationsbibliothek (TIB), 2017. http://d-nb.info/113716400X/34.
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Wang, Yujuan. "Instrumentação optoeletrônica em hardware: implementação de algoritmos otimizados em sensoriamento a FBG." Universidade do Estado de Santa Catarina, 2012. http://tede.udesc.br/handle/handle/2073.
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This work presents the development of an FPGA-based optical interrogation system of multiplexed FBG sensors. The Fabry-Perot filter is used to implement the tunable filter method, as a demodulator for FBG sensors. The tuning signal generation for Fabry-Perot filter and the data aquisition are implemented and syncronized em FPGA. Peak-detection algorithms, based on centroid and FIR filter, are implemented em FPGA. The peak displacement detected of FBG reflected spectrum is used to refer sensed elements, such as variation of temperature and refractive index. Besides, other auxiliary digital circuits are implemented for the system configuration, visulization of the detected peak information and the serial communication to monitor entire spectra in computer. All these digital circuits are working on their own duty at the same time, synchronised by the crystal clock of FPGA. The system was used to monitor the fabrication process of an refractive index sensor. The fabricated sensor was tested by measuring the refractive index of water and sucrose. In another experiment, the system was tested by measuring the temperature of a water sample. In addition, a method to calibrate the tuning signal generator is proposed, which can also be employed in other applications that uses DA converters. Finally, the developed system was packaged to facilitate its transportation.
Este trabalho descreve a implementação de um sistema de interrogação óptico para FBGs multiplexadas, com o controle dos processos implementado em FPGA. A interrogação das FBGs é realizada por meio do método de filtro sintonizável, com o uso de filtro Fabry-Perot. Um FPGA é utilizado para gerar sinal de sintonia para o filtro Fabry-Perot e realizar a leitura do sinal espectral refletido pelas FBGs. Algoritmos de detecção de pico (centroide e filtro FIR) foram implementados no FPGA para processar os sinais refletidos por cada FBG, com o objetivo de inferir as propriedades sensoreadas, como variação de temperatura ou índice de refração. Além destes circuitos digitais, são implementados outros circuitos digitais para a configuração do sistema, para a visualização do pico detectado do sinal espectral e para o monitoramento do espectro inteiro via comunicação serial. Todos circuitos cumprem a própria função paralelamente em virtude do paralelismo do FPGA, sincronizado pelo clock do oscilador cristal do FPGA. O sistema desenvolvido foi utilizado no monitoramento do processo de fabricação de sensor de índice de refração e então na leitura do índice de refração de amostras de sacarose e água. O sistema também foi utilizado para a leitura da temperatura de amostras de água, onde foi estimada a sensibilidade e a resolução do sistema. Também foi proposto um método para a calibração do sistema, que pode ser utilizado também em outros trabalhos. O sistema final foi colocado em uma maleta para facilitar o seu transporte para o local de uso.
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Zhang, Po. "High-resolution Photon Counting OTDR based Interrogation of Multiplexing Broadband FBG Sensors." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/11064.
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Fiber-optic Bragg grating (FBG) sensors are a very attractive technology for the measurement of strain and temperature. They have many advantages over conventional sensors in sensing applications such as sensitivity, immunity to electromagnetic interferences,large bandwidths,capability of remote operation and the potential power to sense micro strain at high temperature. They can be directly embedded into many structures such as concrete to evaluate the material deformation.
FBGs are fabricated by photo-inscribing through a phase mask technology on a photosensitive fiber. A periodic refractive index is formed in the fiber core, introducing a reflection at the Bragg wavelength. Since the FBG is characterized by a low insertion loss and controllable reflectance, it has the potential to be multiplexed in very large numbers.
The major purpose of this dissertation research is to develop an innovative, high- resolution fiber Bragg grating sensing system using photon-counting optical time domain reflectometry (pc-OTDR) based multiplexing technology. The system uses a Fresnel reflection OTDR with a zero deadzone to detect FBG sensors, which improves both the system detection ability and spatial resolution.
A low reflectance FBG with broad bandwidth has been developed that is appropriate for the pc-OTDR measurement. Hundred of multiplexed sensors have been implemented in this system. Two theoretical analyses and preliminary results are presented. The greatest advantage of the system is to increase the maximum multiplexing sensor number to one thousand within a short fiber range.
Self-referencing demodulation is necessary to eliminate multiplexed system noise caused by the source power fluctuation and fiber bending effects. A referencing FBG with a different wavelength from the sensing FBG has to be introduced to achieve compensation of disturbances in the measurement. The spectral properties of the FBGs and the combination of WDM/TDM are also discussed to evaluate multiplexing sensor performance. The sensor crosstalk and other noise performances are assessed to evaluate the possibility of large scale multiplexing.Ph. D.
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Triana, Infante Cristian Andrés. "Enoding optial FBG sensors to enhance the capacity of optial sensing systems." Doctoral thesis, Universitat Politècnica de València, 2018. http://hdl.handle.net/10251/114824.
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Esta tesis investiga la aplicación de conceptos de codificación al diseño de sensores ópticos basados en redes de difracción de Bragg de Bragg (FBG). Específicamente, se presenta el diseño, la caracterización y la validación experimental de dispositivos de detección codificados personalizados que se pueden diseñar y fabricar como dispositivos FBG súper estructurados (SSFBG).
El objetivo de esta tesis es mejorar la capacidad y el rendimiento general de los sistemas de detección óptica basados en sensores FBG convencionales. Para ello, se han propuesto tres metodologías de codificación de dispositivos de detección SSFBG, con el objetivo de dotar a cada sensor con información adicional útil para la identificación de cada sensor incluso en condiciones de superposición. Un sensor codificado basado en FBGs es una estructura FBG cuya forma se ha adaptado a una palabra-código ortogonal, de tal manera que su longitud de onda central se puede distinguir inequívocamente de otras señales en el espectro.
El diseño de los sensores SSFBG codificados se realiza modificando el espectro de reflexión de dispositivos FBG multibanda, esto se logra traduciendo las palabras-código ortogonales en los términos de amplitud y fase de los sensores FBG.
La codificación en amplitud de los sensores SSFBG consiste en traducir las palabras-código \textit{"Optical Orthogonal Codewords"} (OOC), desarrolladas para sistemas de comunicaciones de acceso múltiple por división de código óptico (OCDMA), en el patrón de reflexión de los dispositivos.
La codificación en amplitud y fase se ha propuesto mediante dos enfoques diferentes: en el primero, palabras-código de amplitud y fase personalizadas ($ a_ {k} $, $ f_ {k} $) fueron diseñadas específicamente para exhibir un comportamiento ortogonal obtenido por la combinación de dos palabras-código. La técnica de interrogación basada en una fuente dual sintonizable fue específicamente diseñada para recuperar la medición diferencial de los sensores y decodificar efectivamente su información. El segundo enfoque utiliza las secuencias \textit{"Discrete Prolate Spheroidal Sequences"} (DPSS), que son secuencias mutuamente ortogonales desarrolladas para sistemas de comunicaciones. Se demostró el uso de estas estructuras como elementos de detección ortogonales con patrones específicos de fase y amplitud.
La fabricación y validación experimental de los dispositivos SSFBG propuestos se realizaron para demostrar el rendimiento de los sensores inclusive en condiciones de superposición espectral. La longitud de onda central de los sensores se recupera con éxito en las tres metodologías, además, el error del sistema de detección se caracterizó en términos de los parámetros de diseño.Esta tesi investiga l'aplicació de conceptes de codificació al disseny de sensors òptics basats en xarxes de difracció de Bragg de Bragg (FBG) . Específicament, es presenta el disseny, la caracterització i la validació experimental de dispositius de detecció codificats personalitzats que es poden dissenyar i fabricar com a dispositius FBG súper estructurats (SSFBG) . L'objectiu d'esta tesi és millorar la capacitat i el rendiment general dels sistemes de detecció òptica basats en sensors FBG convencionals. Per a això, s'han proposat tres metodologies de codificació de dispositius de detecció SSFBG, amb l'objectiu de dotar a cada sensor amb informació addicional útil per a la identificació de cada sensor inclús en condicions de superposició. Un sensor codificat basat en FBGs és una estructura FBG la forma de la qual s'ha adaptat a una paraula-codi ortogonal, de tal manera que la seua longitud d'ona central es pot distingir inequívocament d'altres senyals en l'espectre. El disseny dels sensors SSFBG codificats es realitza modificant l'espectre de reflexió de dispositius FBG multibanda, açò s'aconseguix traduint les paraules-codi ortogonals en els termes d'amplitud i fase dels sensors FBG. La codificació en amplitud dels sensors SSFBG consistix a traduir les paraules-codi extit \textit{"Optical Orthogonal Codewords"} (OOC) , desenrotllades per a sistemes de comunicacions d'accés múltiple per divisió de codi òptic (OCDMA) , en el patró de reflexió dels dispositius. La codificació en amplitud i phase s'ha proposat per mitjà de dos enfocaments diferents: en el primer, paraules-codi d'amplitud i fase personalitzades ($ a_ {k} $, $ f_ {k} $) van ser dissenyades específicament per a exhibir un comportament ortogonal obtingut per la combinació de dos paraules-codi. La tècnica d'interrogació basada en una font dual sintonizable va ser específicament dissenyada per a recuperar el mesurament diferencial dels sensors i descodificar efectivament la seua informació. El segon enfocament utilitza les seqüències \textit{"Discrete Prolate Spheroidal Sequences"} (DPSS), que són seqüències mútuament ortogonals desenrotllades per a sistemes de comunicacions. Es va demostrar l'ús d'estes estructures com a elements de detecció ortogonals amb patrons específics de fase i amplitud. La fabricació i la validació experimental dels dispositius SSFBG proposats es van realitzar per a demostrar el rendiment dels sensors inclusivament en condicions de superposició espectral. La longitud d'ona central dels sensors es recupera amb èxit en les tres metodologies, a més, l'error del sistema de detecció es va caracteritzar en termes dels paràmetres de disseny.
This thesis investigates the application of encoding concepts to the design of optical sensors based on fiber Bragg grating (FBG) devices. Specifically, we present the design, characterization and experimental validation of custom encoded sensing devices that can be designed and manufactured as super-structured FBG (SSFBG) devices. The aim of this thesis is to enhance the capacity and the overall performance of the optical sensing systems based on conventional FBG sensors. To do so, three encoding methodologies of SSFBG sensing devices have been proposed, aiming to endow each sensor with additional information useful to identify each sensor even under overlapping conditions. An encoded FBG-based sensor is a FBG structure whose shape has been tailored after an orthogonal codeword in such a way that their central wavelength can be distinguished unequivocally from other signals in the spectrum. The design of encoded SSFBG sensors is performed by modifying the reflection spectrum of multi-band FBG devices, this is achieved by translating orthogonal codewords into the amplitude and phase terms of the FBG sensors. Amplitude encoding of SSFBG sensors consists in translating the binary optical orthogonal codewords (OOCs), developed for optical-code division multiple-access (OCDMA) communications systems, into the reflection pattern of the devices. Amplitude $\&$ phase encoding has been proposed in two different approaches: in the first one, custom amplitude and phase codewords ($a_{k}$, $f_{k}$) were specifically devised to exhibit orthogonal behavior by combining the two codewords. The dual-wavelength tunable interrogation technique was also specifically designed to retrieve the differential measurement of the sensors and effectively decode their information. The second approach uses the discrete prolate spheroidal sequences (DPSS), which are mutually orthogonal sequences developed for communications systems. We demonstrated the use of this structures as orthogonal sensing elements with definite phase and amplitude patterns. The manufacturing and experimental validation of the proposed SSFBG devices were carried out to prove the overlap-proof performance of the devices. The central wavelength of the sensors is successfully retrieved in the three methodologies, additionally, the error of the sensing system was characterized in terms of the design parameters.
Triana Infante, CA. (2018). Enoding optial FBG sensors to enhance the capacity of optial sensing systems [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/114824
TESIS
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Bond, Justin Matthew. "Status Monitoring Of Inflatables By Accurate Shape Sensing." ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/677.
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The use of inflatable structures in aerospace applications is becoming increasingly widespread. In order to monitor the inflation status and overall health of these inflatables, an accurate means of shape sensing is required. To this end, we investigated two existing methods for measuring simple curvature, or curvature in one-dimension. The first method utilizes a pair of strain sensing Fiber Bragg Gratings (FBGs) separated by a known distance; dividing the difference in strain by the separation distance yields an experimental value for the one-dimensional curvature at a point. The second method makes use of conductive ink-based flex sensors, which give a variable resistance based on curvature. We used the latter was in a design for a Curvature-Based Inflation Controller (CBIC). While the controller successfully inflated a test body, its overall utility is limited by the simplicity of its sensors. To improve the shape sensing capabilities of the controller, we investigated the use of FBGs in a multidimensional array.
We fabricated a curvature-sensing FBG pair on an inflatable membrane and tested its accuracy as the membrane was shaped into a known radius of curvature. This work reports on the assembly of three such curvature-sensing FBG pairs into a two-dimensional Curvature-Sensing Rosette (CSR). The goal is to use this rosette to measure the curvature of a surface in multiple directions at a single point. A 3-D printed surface with saddle geometry was used to calibrate the curvature-sensing rosette. Presented will be methods of extracting values for the tensor of curvature for the surface at a point using the curvature-sensing rosette, along with experimental verification. This essentially defines the local geometry about the rosette, measured in real time. By employing an array of such rosettes across the surface of an inflatable structure, the local curvature of the inflatable could be known at every point. Combining these curvature measurements can yield an accurate depiction of the global geometry. Thus, the inflation status of the inflatable space structure could be monitored in real time.
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Yau, Man Hong. "Vertical displacement measurement using fibre Bragg grating (FBG) sensors for structural health monitoring of bridges." Thesis, Queensland University of Technology, 2014. https://eprints.qut.edu.au/72911/2/Man_Hong_Yau_Thesis.pdf.
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This thesis developed a practical, cost effective, easy-to-use method for measuring the vertical displacements of bridges using fiber Bragg grating (FBG) sensors, which includes the curvature and inclination approaches. These approaches were validated by the numerical simulation tests on a full scale bridge and the laboratory-based tests. In doing so, a novel frictionless FBG inclination sensor with extremely high sensitivity and resolution has also been developed and validated.
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Vargas, German R. "Silicon Photonic Device for Wavelength Sensing and Monitoring." FIU Digital Commons, 2012. http://digitalcommons.fiu.edu/etd/734.
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Over the last decade advances and innovations from Silicon Photonics technology were observed in the telecommunications and computing industries. This technology which employs Silicon as an optical medium, relies on current CMOS micro-electronics fabrication processes to enable medium scale integration of many nano-photonic devices to produce photonic integrated circuitry.
However, other fields of research such as optical sensor processing can benefit from silicon photonics technology, specially in sensors where the physical measurement is wavelength encoded.
In this research work, we present a design and application of a thermally tuned silicon photonic device as an optical sensor interrogator.
The main device is a micro-ring resonator filter of 10 $\mu m$ of diameter. A photonic design toolkit was developed based on open source software from the research community. With those tools it was possible to estimate the resonance and spectral characteristics of the filter. From the obtained design parameters, a 7.8 x 3.8 mm optical chip was fabricated using standard micro-photonics techniques. In order to tune a ring resonance, Nichrome micro-heaters were fabricated on top of the device. Some fabricated devices were systematically characterized and their tuning response were determined. From measurements, a ring resonator with a free-spectral-range of 18.4 nm and with a bandwidth of 0.14 nm was obtained. Using just 5 mA it was possible to tune the device resonance up to 3 nm.
In order to apply our device as a sensor interrogator in this research, a model of wavelength estimation using time interval between peaks measurement technique was developed and simulations were carried out to assess its performance. To test the technique, an experiment using a Fiber Bragg grating optical sensor was set, and estimations of the wavelength shift of this sensor due to axial strains yield an error within 22 pm compared to measurements from spectrum analyzer. Results from this study implies that signals from FBG sensors can be processed with good accuracy using a micro-ring device with the advantage of ts compact size, scalability and versatility. Additionally, the system also has additional applications such as processing optical wavelength shifts from integrated photonic sensors and to be able to track resonances from laser sources.
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Suleiman, Maha. "Conception d'un capteur optoélectronique par interférométrie à rétro-injection optique pour la démodulation des signaux de fibres optiques à réseaux de Bragg." Toulouse, INPT, 2008. http://ethesis.inp-toulouse.fr/archive/00000702/.
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Nous proposons, dans cette thèse, une nouvelle technique de démodulation des variations de la longueur d'onde centrale d'une FBG (Fiber Bragg Grating) qui a pour principe l'interférométrie à rétro-injection optique dans une cavité laser longitudinale monomode (ou « self-mixing interferometry »). Le capteur conçu complet comprend une diode laser avec une photodiode intégrée qui est couplée à une FBG sous contraintes. Une partie de la lumière émise par le laser est réfléchie par la FBG et ensuite rétro-injectée dans la cavité laser, modifiant ainsi les propriétés du laser et engendrant des phénomènes non linéaires exploitables pour mesurer les perturbations induites sur la FBG. Les franges résultantes ou les signaux typiques du phénomène de self-mixing qui sont en forme de dents de scie peuvent être obtenus pour une FBG subissant une déformation mécanique et peuvent être interprétés pour extraire les informations pertinentes à la perturbation appliquée sur la FBGIn this thesis, we propose post-transforms for the compression of satellite images. After the wavelet transform, each block of coefficients is further transformed in a basis selected among a dictionary by minimization of a rate-distortion criterion. First, we optimize the bandelet transform parameters, from which the post-transforms derive, for the compression of satellite images. Next, we analyze dependencies between wavelet coefficients that are not exploited by the bandelet transform and we define new post-transform bases. Bases build by PCA minimize the correlations between post-transformed coefficients and compact the energy of each block on a small number of coefficients. This feature is exploited during the entropy coding process. Last, we adapt the post-transform to progressive compression schemes. We then employ the Hadamard post-transform with the CCSDS image encoder to obtain a low computational complexity yet efficient compression scheme
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Akter, Afroja. "Gap Solitons in a Coupled FBGs with Cubic-quintic Nonlinearity and Dispersive Reflectivity." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/23994.
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This thesis presents a comprehensive analysis of optical gap solitons in linearly coupled fibre Bragg gratings with higher-order nonlinearity, such as cubic-quintic nonlinearity and grating non-uniformity. The non-uniformity is accounted for with a dispersive reflectivity parameter. We find two disjointed families of solitons—named Type 1 and Type 2 gap solitons—in the entire bandgap. The Type 1 family shows the generalised behaviour of Kerr nonlinearity. In contrast, where quintic nonlinearity shows dominant behaviour, we find Type 2 solitons. Moreover, each family presents asymmetric and symmetric type solitons. There is no analytic solution to this model; hence, all the solutions for quiescent or moving gap solitons are found via a systematic numerical approximation, such as relaxation technique in the (η, ω) plane. The solutions have any velocity from zero to the speed of light in the medium. For a given soliton, there is a critical coupling coefficient where bifurcation has occurred and, beyond that point, only symmetric Type 1 solitons can exist. However, in the case of Type 2 solitons, there is no bifurcation. The border between Type 1 and Type 2 asymmetric solitons is found numerically. The stability of zero velocity solitons is investigated by employing numerical split-step Fourier technique and Runge-Kutta or RK4 method. The effect of dispersive reflectivity and coupling coefficient on the stability region of quiescent solitons in (η, ω) is analysed. The results indicate that the presence of dispersive reflectivity has a stabilisation effect on both Type 1 and Type 2 quiescent solitons, especially for Type 2 solitons we found that presence of the dispersive reflectivity has broadened the stable region significantly for a lower value of coupling coefficient. We find a significant region of stable Type 1 asymmetric zero velocity solitons. In the region where only symmetric Type 1 solitons can exist are highly stable. In contrast, all symmetric Type 2 solitons are highly unstable. However, after the propagation of unstable asymmetric Type 1 and symmetric Type 2 zero velocity solitons, they can generate stable moving solitons belonging to asymmetric Type 1 solitons. This study also investigates the stability of moving gap solitons, where the effect of dispersive reflectivity, coupling coefficient and the initial velocity of the moving gap solitons are considered. The results indicate that, in the case of the coupled Kerr nonlinear model, the initial velocity is insignificant in the stability of moving gap solitons. However, in this case, the initial velocity, dispersive reflectivity and coupling coefficient have a significant effect on the stable region of the moving gap solitons. Similar to their quiescent counterpart, the stable region shrinks with increasing coupling coefficient and broadens as dispersive reflectivity increases at a fixed initial velocity. This study also investigates the interaction and collision dynamics of two counterpropagating zero velocity and moving gap solitons, respectively. The presence of dispersive reflectivity brings some novel features in the case of interactions and collisions. For example, we observe some exceptional behaviour in the case of in-phase interactions and collisions of Type 2 zero and moving gap solitons, respectively, such as prevention of complete destruction of in-phase Type 2 quiescent gap solitons after their interactions for weak to moderate values of dispersive reflectivity. Another noteworthy finding is the generation of the merger to quiescent solitons from the in-phase collision of two Type 2 moving gap solitons, when higher-order dispersive reflectivity is presented. For weak to moderate values of dispersive reflectivity, the in-phase interactions of asymmetric Type 1 quiescent solitons can generate various outcomes, such as a merger, two-to-three solitons, symmetric and asymmetric separation of the solitons, and destruction of the solitons. However, for strong dispersive reflectivity interactions, the outcomes significantly alter their behaviour. As a result, we find repulsion solitons after their interactions of two in-phase Type 1 asymmetric solitons. Other typical outcomes at this condition are temporary bound state to asymmetric separation, merger and so on. On the other hand, interactions of two in-phase Type 2 asymmetric solitons can produce a temporary bound state to a single moving soliton, separation of both solitons and destruction. Initial attraction to destruction and repulsion to separation solitons are also possible from the in-phase interactions of Type 2 asymmetric solitons with strong dispersive reflectivity. Additionally, this study analyses the effect of initial separation and phase difference of two quiescent solitons on their outcomes. We also investigate the out-of-phase interactions of both Type 1 and Type 2 zero velocity solitons in the case of weak to moderate dispersive reflectivity and strong dispersive reflectivity. The asymmetric interactions of two quiescent solitons, where solitons are from two different cores, are also investigated. In the case of in-phase collisions of two Type 1 asymmetric non-zero velocity or moving gap solitons, the general outcomes are merger, two-to-three solitons, symmetric separation with reduced and increased velocity, asymmetric separation with two different velocities, destruction, and repulsion of solitons. For the in-phase collisions of two Type 2 moving solitons, we find asymmetric separation, repulsion, merger and destruction when strong dispersive reflectivity is present. Moreover, we find merger solitons in the case of π outof-phase collision of Type 2 asymmetric moving solitons. Further, in the case of collision dynamics, we investigate the effect of initial phase difference and velocity mismatch on the various outcomes of in-phase collisions. We find that the initial phase difference (velocity mismatched) can be tuned to compensate for the initial velocity mismatch (phase difference) to obtain similar results to those found for in-phase collisions. This thesis also investigates the collisions of exchange components of two Type 1 and Type 2 non-zero velocity gap solitons.
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SANTOS, Adam Dreyton Ferreira dos. "Proposta de gerenciamento de dados para monitoramento de saúde estrutural utilizando redes de sensores ópticos FBG." Universidade Federal do Pará, 2014. http://repositorio.ufpa.br/jspui/handle/2011/5603.
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CVRD - Companhia Vale do Rio Doce
FAPESPA - Fundação Amazônia de Amparo a Estudos e Pesquisas
CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Devido às suas características únicas, redes de sensores ópticos têm encontrado aplicação em muitos campos, como em Engenharia Civil, Engenharia Geotécnica, Aeronáutica, Energia e Indústrias de Petróleo & Gás. Soluções de monitoramento baseadas nessa tecnologia têm se mostrado particularmente rentáveis e podem ser aplicadas às estruturas de grande porte, onde centenas de sensores devem ser implantados para medições a longo prazo de diferentes parâmetros mecânicos e físicos. Sensores baseados em Grades de Bragg em fibra (FBGs) são a solução mais comumente utilizada no Monitoramento de Saúde Estrutural (SHM) e as medições são realizadas por instrumentos especiais conhecidos como interrogadores ópticos. Taxas de aquisição cada vez mais elevadas têm sido possíveis utilizando interrogadores ópticos mais recentes, o que dá origem a um grande volume de dados cuja manipulação, armazenamento, gerenciamento e visualização podem demandar aplicações de software especiais. Este trabalho apresenta duas aplicações de software de tempo real desenvolvidas para esses fins: Interrogator Abstraction (InterAB) e Web-based System (WbS). As inovações neste trabalho incluem a integração, sincronização, independência, segurança, processamento e visualização em tempo real, e persistência de dados ou armazenamento proporcionados pelo trabalho conjunto das aplicações desenvolvidas. Os resultados obtidos durante testes em laboratório e ambiente real demonstraram a eficiência, robustez e flexibilidade desses softwares para diferentes tipos de sensores e interrogadores ópticos, garantindo atomicidade, consistência, isolamento e durabilidade dos dados persistidos pelo InterAB e apresentados pelo WbS.
Due to their unique characteristics, optical sensor networks have found application in many fields, such as in Civil and Geotechnical Engineering, Aeronautics, Energy and Oil & Gas Industries. Monitoring solutions based on this technology have proven particularly cost effective and can be applied to large scale structures where hundreds of sensors must be deployed for long term measurement of different mechanical and physical parameters. Sensors based on Fiber Bragg gratings (FBGs) are the most common solution used in Structural Health Monitoring (SHM) and the measurements are performed by special instruments known as optical interrogators. Acquisition rates increasingly higher have been possible using the latest optical interrogators, which gives rise to a large volume of data whose manipulation, storage, management and visualization can demand special software applications. This work presents two real-time software applications developed for these purposes: Interrogator Abstraction (InterAB) and Web-based System (WbS). The innovations in this work include the integration, synchronization, independence, security, processing and real-time visualization, and data persistence or storage provided by joint work of developed applications. The results obtained during tests in laboratory and real environment demonstrate the efficiency, robustness and flexibility of these softwares for different types of sensors and optical interrogators, ensuring atomicity, consistency, isolation and durability of data persisted by InterAB and displayed by WbS.
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Fussangel, Kathrin. "Subjektive Theorien von Lehrkräften zur Kooperation : eine Analyse der Zusammenarbeit von Lehrerinnen und Lehrern in Lerngemeinschaften." kostenfrei, 2008. http://elpub.bib.uni-wuppertal.de/edocs/dokumente/fbg/paedagogik/diss2008/fussangel.
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Achterberg, Susanne. "Intime Nachrichten : die geschlechtliche und generationale Ordnung in sexuellen Aufklärungsratgebern für Jugendliche." kostenfrei, 2007. http://elpub.bib.uni-wuppertal.de/edocs/dokumente/fbg/soziologie/diss2008/achterberg.
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Seo, Bo-Kyung. "Ereignis- und bewegungskorrelierte evozierte Potentiale und kognitive Leistung bei der Aufmerksamkeitsdefizit-, Hyperaktivitätsstörung (ADHS) im Erwachsenenalter." kostenfrei, 2008. http://elpub.bib.uni-wuppertal.de/edocs/dokumente/fbg/psychologie/diss2008/seo.
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Colpo, Fabiano. "Residual stress characterization in a single fibre composite specimen by using FBG sensor and the OLCR technique /." [S.l.] : [s.n.], 2006. http://library.epfl.ch/theses/?nr=3533.
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Baños, López Rocío. "Diseño y caracterización de dispositivos codificadores y decodificadores para sistemas OCDMA Coherentes." Doctoral thesis, Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/52022.
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[EN] In this thesis we propose the design and characterization of advanced optical de- vices used in coherent direct sequence optical en/decoding, also called temporal phase en/decoding, based on SSFBGs (Super-Structured Fiber Bragg Grating). The aim of this thesis is to enhance the overall performance of the proposed devi- ces used in optical en/decoding and their characteristics, such as: insertion losses and reflectivity, spectral bandwidth, spectral efficiency and chromatic dispersion present in the optical fiber used in the Telecommunication network.
To achieve this goal, modifications in the design and fabrication process were pro- posed.
Additionally, encoder and decoder integrated devices based on (Silicon On Insu- lator technology), were presented. The design of the integrated devices is based on unit cells, which are composed of directional couplers, delay lines and thermo- optical heaters. The use of thermo-optical structures enables the code to be tuned. The characteristics of the devices, along with the most important related parame- ters were defined accurately for both technologies. Furthermore, a mathematical model was developed for the encoding and decoding process ,and the results of simulations are shown.
The experimental encoding and decoding process was carried out using SSFBGS devices, and hybrid experiments were also performed using integrated devices with SSFBGs, demonstrating that all the technologies are completely compatible. Finally, a characterization methodology based on optical single side band was deve- loped in order to achieve complete frequency characterization (modulus and phase) of the optical devices proposed, leading to the recovery of the impulse response.[ES] En este trabajo se propone el diseño y caracterización de dispositivos ópticos avanzados para aplicaciones de codificación óptica en secuencia directa coherente, también denominada codificación temporal en fase, basados en SSFBGs (Super- Structured Fiber Bragg Grating). El objetivo de la tesis es mejorar el comportamiento general de los dispositivos propuestos para la codificación óptica y el de sus características, como lo son: pér- didas de inserción y reflectividad, ancho de banda de los dispositivos, eficiencia espectral y finalmente el comportamiento frente a la dispersión cromática presente en la fibra óptica utilizada en la red de telecomunicaciones. Para alcanzar dicho objetivo se proponen modificaciones en el proceso de diseño y fabricación de los dispositivos basados en fibra. Adicionalmente, se presenta la implementación de estos dispositivos codificadores y decodificadores en tecnología integrada basada en silicio (SOI, Silicon on Insu- lator), cuyo diseño está basado en celdas unitarias compuestas por acopladores direccionales, líneas de retardo y desfasadores termo-ópticos, que permite la sin- tonización de los códigos. Para ambas tecnologías se definen con precisión los dispositivos necesarios y sus parámetros más importantes, se desarrolla el modelo teórico matemático y se mues- tran los resultados de simulación del proceso de codificación y decodificación. Diferentes montajes experimentales son llevados a cabo para verificar el proceso de codificación y decodificación para los dispositivos en fibra; así como la verificación conjunta de dispositivos integrados y SSFBGs, presentando la total compatibili- dad entre las tecnologías. Para finalizar, se desarrolla una metodología basada en la modulación en banda lateral única, para la caracterización frecuencial completa (módulo y fase) de los dispositivos bajo estudio, permitiendo la recuperaicón de su respuesta impulsiva.
[CAT] En aquest treball es proposa el disseny i caracterització de dispositius òptics ava- nçats basats en SSFBGs (Super-Structured Fiber Bragg Grating) per a aplicacions de codificació òptica en seq üència directa coherent, també anomenada codificació temporal en fase. L'objectiu de la tesi és millorar el comportament general dels dispositius propo- sats per a la codificació òptica i les seves característiques com pèrdues d'inserció i reflectivitat, amplada de banda dels dispositius, eficiència espectral i finalment el comportament davant la dispersió cromàtica present en la fibra òptica utilitzada en la xarxa de telecomunicacions. Per assolir aquest objectiu es proposen modificacions en el procés de disseny i fa- bricació dels dispositius basats en fibra. Addicionalment, es presenta la implementació d'aquests dispositius codificadors i descodificadors en tecnologia integrada basada en silici (SOI, Silicon on Insulator). El disseny està basat en celáles unitàries compostes per acobladors direccionals, lí- nies de retard i desfasadors termo-òptics, que permeten la sintonització dels codis. Per a ambdues tecnologies es defineixen amb precisió els dispositius necessaris i els seus paràmetres més importants. També es desenvolupa el model teòric matemàtic i es mostren els resultats de simulació del procés de codificació i descodificació. Així mateix, per a verificar el procés de codificació i descodificació dels disposi- tius en fibra, a més de la verificació conjunta de dispositius integrats i SSFBGs, s'utilitzen diferents muntatges experimentals. Així doncs es presenta la total com- patibilitat entre les tecnologies. Per finalitzar, es desenvolupa una metodologia basada en la modulació en banda lateral única per a la caracterització freqüencial completa (mòdul i fase) dels dis- positius baix estudi. D'aquesta manera es permet la recuperació de la seva resposta a l'impuls.
Baños López, R. (2015). Diseño y caracterización de dispositivos codificadores y decodificadores para sistemas OCDMA Coherentes [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/52022
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Silva, Gleison Elias da. "Desenvolvimento de transdutor em fibra óptica com estrutura híbrida LPG-FBG para medição de propriedades térmicas de materiais." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-27022018-102025/.
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Este trabalho apresenta o estudo, a implementação e a caracterização de transdutores compostos por uma estrutura formada por grades de Bragg (FBG, Fiber Bragg Gratings) e grades de período longo (LPG, Long Period Gratings) em fibra óptica com cobertura metálica autoaquecida para medição da condutividade térmica e da difusividade térmica de materiais baseado no método do fio quente (HWM, Hot-Wire Method) convencional. O autoaquecimento da fibra óptica do dispositivo desenvolvido neste trabalho é provocado pela luz de espectro infravermelho injetada por um laser de bombeamento, que é espalhada por uma LPG e absorvida por um filme fino metálico depositado na superfície da fibra. Os transdutores apresentados são compactos, simples, robustos e imunes a interferências eletromagnéticas. O arranjo experimental utilizando o dispositivo híbrido LPG-FBG foi capaz de medir as condutividades térmicas do ar atmosférico e da água comum com precisões de 27% e 14%, respectivamente. Foram identificados vários fatores que afetam a precisão e a exatidão das medidas realizadas, sendo propostas diversas formas de correções de modo a melhorar o desempenho do arranjo. Foi demonstrada com sucesso a viabilidade da aplicação original do arranjo experimental utilizando o dispositivo híbrido LPG-FBG em fibra óptica autoaquecida para a medição de propriedades térmicas de fluidos (ar e água).This work presents the study, implementation, and characterization of transducers composed of a structure formed by Fiber Bragg Gratings (FBG) and Long Period Gratings (LPG) in optical fiber with self-heating coverage for measurement of thermal conductivity and thermal diffusivity of materials based on the Hot-Wire Method (HWM). The self-heating fiber optic device developed in this work is caused by the light of infrared spectrum injected by a pumping laser, which is spread by an LPG and absorbed by a thin metallic film deposited on the surface of the fiber. The transducers are compact, simple, robust and immune to electromagnetic interference. The experimental arrangement using the optical fiber sensor based on LPG-FBG hybrid structure was able to measure the thermal conductivity of atmospheric air and water with accuracies of 27% and 14%, respectively. Several factors were identified that affect the precision and the accuracy of the measures carried out, whereby various forms of corrections are being proposed to improve overall performance. The viability of the original application of the experimental arrangement using the LPG-FBG hybrid device in self-heating optical fiber for the measurement of thermal properties of fluids (air and water) has been successfully demonstrated.
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Hasanovic, Selma. "Metformin eller insulin vid behandling av graviditetsdiabetes : Effekten av metformin versus insulin vid sänkning av FBG och 2-hr PG." Thesis, Linnéuniversitetet, Institutionen för kemi och biomedicin (KOB), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-104187.
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Gestational diabetes mellitus (GDM ) is a disease that appears during pregnancy due to an insulin resistance. GDM is associated with increased risks for complications both to the mother and the child during pregnancy. These risks include conditions such as neonatal macrosomi and hypoglycemia for the child. This leads to increased risk for cesarean section and birth injuries. GDM can be treated with a changed diet supported with exercise. If the blood glucose levels still remain high, insulin or metformin medication can be introduced to treat the patient. Metformin is a safe and effective anti-diabetic drug and it is used as a treatment for GDM. Since the treatment during GDM varies, the effect of insulin versus metformin was examined. The aim of this litterature study was to compare the treatment with metformin versus insulin and to investigate the differences between the two drugs in the treatment of GDM. The medical databases PubMed and Google Scholar were used to search for clinical studies that compare the effects of the two treatments. Four studies were selected for this litterature study. The results in this study indicated that both insulin and metformin are effective as glucose lowering drugs in the treatment of GDM. All patients do not respond to metformin and therefore insulin may be preferable in the treatment of some patient. Both insulin and metformin lead to better glycemic control in GDM patients. Both drugs are safe and effective but metformin has several advantages. The cost is low, it is easier to use and leads to fewer cases of hypoglycemia compared to insulin, even though all patients do not respond to metformin, it is considered a good alternative.
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Fung, Wing Wah. "Lightly cemented rubber tire chips as highway pavement sub-base and the use of fiber Bragg's grating (FBG) as instrumentation sensors /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20FUNG.
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Gardáš, Vít. "Analýza signálů ze senzorických systémů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-376960.
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This master’s thesis is focused on sensory systems and analysis of such signals. In the frst part, a theoretical analysis of each sensory system is conducted. Followingly, appropriate flters were used to process these signals. The last part of this thesis deals with the analysis of measured data.
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Muci, Elgi. "Ottimizzazione del posizionamento di sensori ottici per il monitoraggio strutturale." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23466/.
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Tutte le strutture, che si tratti di aeromobili, navi, ponti, impianti eolici, condotte idrauliche, o altro, sono soggette a svariati fattori, interni ed esterni, che possono provocare usura o malfunzionamenti. Le cause scatenanti possono essere, ad esempio: il deterioramento, un processo di costruzione non effettuato a regola d’arte, la mancanza di controlli di qualità o una situazione estrema (come un incidente o condizioni ambientali estreme).
Per riuscire a osservare questi cambiamenti nel materiale e a reagire in modo corretto prima che ne conseguano gravi danni, è fondamentale implementare un sistema di individuazione dei danni. Il monitoraggio del comportamento strutturale può rilevare per tempo eventuali anomalie, consentendo un’attuazione più efficiente degli interventi di manutenzione e riparazione, con conseguente riduzione dei costi operativi. Nella structural health monitoring i sensori in fibra ottica sono molto promettenti per i monitoraggi in tempo reale e, in particolare, sapere come posizionare i sensori ottici è una qualità molto importante per quanto riguarda l’analisi, il controllo ed il monitoraggio di queste strutture. Anche se esistono tanti tipi di sensori ed attuatori per il monitoraggio strutturale, che variano in base al campo di applicazione, la metodologia utilizzata per l’ottimizzazione del posizionamento di sensori ottici è pressoché la stessa indipendentemente dall’applicazione. Gli approcci differiscono prevalentemente nella scelta della funzione finale e, quindi, dell’algoritmo di ottimizzazione, pertanto, è utile approfondire la letteratura sul posizionamento dei sensori in altri campi da trattare con il posizionamento del sensore per un'applicazione specifica. In questo elaborato verranno riassunti quali sono i metodi di posizionamento di sensori in fibra ottica e i relativi algoritmi di optimal sensor placement per il monitoraggio strutturale.
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Lanzoni, Maicol. "Applicazione di reticoli di Bragg "chirped" per il monitoraggio strutturale di laminati CFRP." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/8512/.
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L’uso dei materiali compositi è andato aumentando negli ultimi decenni per la loro elevata rigidezza, la resistenza specifica e il possibile risparmio, notevole in termini di peso dell’intera struttura.
Tali materiali introducono però nuove problematiche riguardanti le modalità di danneggiamento e il comportamento a fatica. Mentre questi fenomeni sono relativamente ben compresi nei materiali metallici, per una struttura in composito non esistono ancora modelli in grado di predire con sufficiente affidabilità l’evoluzione del danneggiamento.
Negli ultimi anni la ricerca si è focalizzata sullo sviluppo di sistemi in grado di rilevare la presenza e l’evoluzione del danno, definiti Structural Health Monitoring Systems, ovvero sistemi di monitoraggio strutturale.
Il danneggiamento strutturale può così essere individuato e identificato per mezzo di sensori distribuiti integrati nella struttura stessa, aventi la possibilità di trasmettere queste informazioni a un sistema di analisi esterno permettendo di valutare lo stato di degrado della struttura in tempo reale.
In questo contesto si inseriscono le attività di ricerca sulle strutture intelligenti che, inglobando al loro interno opportune tipologie di sensori e attuatori, sono in grado di monitorare l’ambiente fisico operativo, raccoglierne e interpretarne le informazioni per poi rispondere ai cambiamenti della struttura in modo appropriato attraverso gli attuatori.
L’impiego di sensori e attuatori inglobati nelle strutture offre molteplici vantaggi rispetto ai sistemi di trasduzione e attuazione convenzionali.
L’attività di ricerca condotta in questa tesi è rivolta all’indagine di tecniche di SHM per mezzo di sensori a fibra ottica. Essi presentano molteplici peculiarità che li rendono i candidati ideali per queste applicazioni.
Esistono diversi tipi di sensori che utilizzano le fibre ottiche. Nel presente lavoro si sono utilizzati sensori di deformazione basati sui reticoli di Bragg (FBG) chirped. Questi sensori sono costituiti da un reticolo inscritto all’interno della fibra, che ha l’effetto di riflettere solo alcune lunghezze d’onda della luce incidente. Se le proprietà geometriche del reticolo cambiano per effetto di una deformazione, cambia anche la forma dello spettro riflesso. Inoltre, con il tipo di sensore usato, è possibile correlare lo spettro con la posizione di eventuali danneggiamenti interni al materiale.
Gli obbiettivi di questa ricerca sono di verificare gli effetti della presenza di una fibra ottica sulle caratteristiche meccaniche di un laminato e di trovare un legame tra la risposta in frequenza del sensore FBG e lo stato tensionale e il grado di danneggiamento di un componente in composito.
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Castellanos, Carlos. "Development of a validation shape sensing algorithm in Python with predictive and automatedanalysis." Thesis, Uppsala universitet, Avdelningen för systemteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-454942.
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Difficulties with wind turbines can arise during operation due to externalforces provoked by the wind. Calculating the deflection of the blades can beused to give break points for maintenance, design and/or monitoring purposes. Fiber Bragg Grating (FBG) sensors can be installed on the windblades to detect signals that can be reinterpreted as deflection in differentdirections. In this project a tool was developed that can take this information in real time to analyze critical issues which is important to save timeand operational and maintenance costs (O&M). To do so, a predictive model is used to anticipate the deflection in the blades caused by the impact ofthe wind in different orientations. The main purpose of this work is to showan algorithm that can transform optical signals from the FBG sensors into ashape calculator for the deflection for maintenance purposes. At the sametime, it is shown that this algorithm can be used as a forecast tool takinginto consideration the weather data.
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Al-Tarawneh, Mu'ath. "Traffic Monitoring System Using In-Pavement Fiber Bragg Grating Sensors." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/31539.
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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.
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da, Silva Falcao Bruno. "CO2-rock interaction during CO2-enriched brine injection into storage reservoirs using NMR integrated with fiber optic sensors." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2022. https://ro.ecu.edu.au/theses/2505.
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The combustion of fossil fuels has led to a global temperature increase due to the emission of carbon dioxide, which is the major contributor to global warming. The mitigation of CO2 emissions into the atmosphere is therefore critical, where new technologies need to be urgently developed and employed on a large scale. One promising method is to capture anthropogenic CO2 and store it in geological formations, e.g. depleted oil and gas reservoirs and saline aquifers. This process is referred to as carbon capture and storage (CSS).
The storage of CO2 in depleted oil and gas reservoirs that have trapped hydrocarbons for millions of years, requires the evaluation of their storage capacity as well as CO2 leakage risks to ensure long-term safety. Therefore, reservoir conditions need to be monitored, namely pressure and strain changes to avoid compromising the geo-mechanical strength of the reservoir rock, which could reactivate faults and lead to pathways for CO2 leakages. Rock strain is conventionally evaluated by linear variable differential transformers (LVDT) and electrical resistance strain gauges (ESG) that are attached to a rock sample’s surface. However, the geo-mechanical response obtained under laboratory conditions often mismatches with the response of an underground rock formation due to heterogeneity and anisotropy that are not captured by LVDT and ESG. Therefore, Fiber Bragg Grating (FBG) sensing has become a promising alternative due to its various advantages, such as resistance to electromagnetic interference, high-pressure and -temperature, small size, multiplexing capability, amongst others. In this study, FBG sensing technology was applied to measure strain changes in uniaxial compressive strength (UCS) and hydrostatic compressive tests of a standard plexiglass (PMMA) and limestone rock samples. The FBG fiber was wrapped around the samples in a helix with circumferential loops alongside the sample. To allow strain transfer, the fiber was glued onto the sample surface using Loctite Super Glue. The results showed that the FBG sensors were capable of accurately monitoring strain changes during UCS and hydrostatic compressive tests. Conventional methods were employed for comparison. The measured strain changes by FBG showed significantly higher precision and lower noise compared to the results obtained by LVDT and ESG.
Rock permeability, porosity, fluid saturation and flow characteristics are essential information required to design any CCS project, and are commonly measured by core flooding experiments using nuclear magnetic resonance (NMR). However, NMR is not capable of measuring rock deformation caused by fluid migration. Therefore, the evaluation of the rock sample surface deformation during core flooding has been investigated by associating NMR with FBG sensing technology. An optical fiber with 8 FBG sensors was attached to a Savonnières limestone sample and subsequently mounted to a GeoSpec2 (Oxford Instruments) NMR core analyzer. Brine was injected into the sample at 0.1 cc/min, whilst obtaining saturation profiles by the NMR and simultaneously measuring strain changes by the FBG. The results showed the FBG sensors to be capable of tracking the fluid migration through the sample at a high resolution, and to be in excellent agreement with the saturation profiles measured by NMR. As a result, the association of NMR and FBG has been demonstrated as a very promising tool to monitor fluid injection and strain changes during core flooding experiments.
Tests were conducted to monitor interactions between CO2 and the rock samples. The injected CO2 produces a weak carbonic acid in the presence of formation water that can react with calcite within the rock causing ion dissolution and the formation of secondary minerals. This can in turn lead to significant changes in the geo-mechanical strength of the rock, where it is extremely important for CCS projects to ensure safe long-term CO2 storage. Two sandstone rock samples were used to investigate the injection of live brine – CIPS-2 and CIPS-3. CIPS is an artificial sample consisting of quartz with cement composed by calcite. The CIPS-2 sample was used for the static aging process to evaluate the effect of the CO2 far from the injection point. The CIPS-3 sample was used for the dynamic aging to appraise the CO2 effects near the injection point. The aging process ran for approximately 40 hours, which was long enough to demonstrate that the reaction occurred in the bottom of the samples, with CIPS-3 presenting a stronger mineral dissolution. The changes in the samples internal structure were confirmed by CT scan images and NMR measurements. The FBG sensors were able to track strain changes at this specific location of the sample, allowing for quantification of changes in the geo-mechanical strength of the rock sample caused by the reaction of CO2 with calcite.
Overall, FBG sensing technology has been used in this study to accurately measure geo-mechanical rock strain properties at a significantly lower noise level and higher precision than conventional sensors. Further, the association of NMR with FBG sensing technology has been demonstrated in the study. Strain changes were measured at high accuracy during the core flooding process, allowing for tracking of fluid migration within a rock sample. In addition, the strain changes were shown to be related to the rock structure, confirmed by CT scanning images prior to and after the experiment. Possible changes to the rock structure caused by the reaction of dissolved CO2 and the rock were also tracked via FBG technology, allowing for monitoring of the reservoir’s geo-mechanical strength. This is an essential property to ensure the long-term safety of CO2 storage reservoirs.
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Kunzler, Wesley Mont. "Fiber Optic Sensor Interrogation Advancements for Research and Industrial Use." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2608.
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Spectrally-based fiber optic sensors are a rapidly maturing technology capable of sensing several environmental parameters in environments that are unfitting to electrical sensors. However, the sensor interrogation systems for this type of sensors are not yet fit to replace conventional sensor systems. They lack the speed, compact size, and usability necessary to move into mainstream test and measurement. The Fiber Sensor Integrated Monitor (FSIM) technology leverages rapid optical components and parallel hardware architecture to move these sensors across the research threshold into greater mainstream use. By dramatically increasing speed, shrinking size, and targeting an interface that can be used in large-scale industrial interrogation systems, spectrally-based fiber optic sensors can now find more widespread use in both research labs and industrial applications. The technology developed in this thesis was demonstrated by producing two advanced interrogators: one that was one half the size of commercially available systems, and one that accelerated live spectral capture by one thousand times – both of which were operated by non-developers with little training.
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Argelli, Michael. "Monitoraggio strutturale (structural health monitoring) di laminati CFRP tramite reticoli di Bragg in fibra ottica." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6729/.
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Lo studio si propone di valutare la capacità dei reticoli di Bragg in fibra ottica, di individuare e monitorare danneggiamenti presenti all'interno di laminati in composito, tramite l'analisi degli spettri riflessi dai reticoli stessi. Sono stati utilizzati due tipi diversi di stratificazione dei laminati, per valutare il diverso comportamento dei reticoli di Bragg inseriti all'interno dei laminati.
Le proprietà dei materiali e degli spettri riflessi dai reticoli, sono state messe in relazione qualitativamente e quantitativamente, al fine di sviluppare un valido metodo di Structural Health Monitoring.
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Sancho, Durá Juan. "Photonic-assisted RF Signal Processing based on Slow and Fast Light Technological Platforms." Doctoral thesis, Universitat Politècnica de València, 2012. http://hdl.handle.net/10251/16471.
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Los efectos de la luz lenta y luz rápida (SFL) han mostrado unas capacidades excepcionales sobre el control dinámico de la velocidad de la luz en diferentes medios. Una de las motivaciones más estimulantes redica en la potente aplicación de estos sistemas en el marco del procesado fotónico de señales de radio frecuencia (RF).
En esta tesis doctoral, se evalúan las prestaciones de las plataformas de SFL actuales para desarrollar múltiples tareas que se requieren en el campo de la fotónica de microondas (MWP) con el valor añadido de sintonizabilidad y operación en banda ancha. En esta contexto, el scattering de Brillouin estimulado (SBS) tanto en fibra estándar como en fibra mantenedora de polarización (PMF), de redes Bragg (FBG), amplificadores ópticos de semiconductor (SOA) y cristales fotónicos (PhC) han sido las tecnologías bajo estudio. Desde escalas del orden de km hata mm, estas plataformas de SFL representan la evolución hacia la consolidación de componentes y subsistemas de MWP en circuitos fotónicos integrados (PIC). Diversos modelos analíticos y numéricos se han desarrollado con el objetivo de entender los procesos físicos que goboernan la porpagación a través de las diferentes plataformas de SFL, así como para describir los enfoques de MWP propuestos. Además, a través de las plataformas presentadas se ha llevado a cabo el análisis de las prestaciones de dos de las funcionalidades clave que se requieren para el procesado fotónico de señales de microondas, desfasadores sintonizables y retardos verdaderos (TTD). Se ha propuesto un sistema de TTD basado en la llamada técnica de sintonización separada de la portadora (SCT) a través de los efectos de SBS en fibrras estándr. Se ha evaluado la interacción del SBS en PMF con el propósito de desarrollar redes de Brillouin dinámicas (DBG), cuya fase generada ha sido fruto de estudio. Por otro lado, también se ha demostrado un sistema de densado distribuido basado en la reflexión continua de un pulso estrecho a lo laSancho Durá, J. (2012). Photonic-assisted RF Signal Processing based on Slow and Fast Light Technological Platforms [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/16471
Palancia
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Chilelli, Sean Kelty. "Structural health monitoring with fiber Bragg grating sensors embedded into metal through ultrasonic additive manufacturing." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1563529169604482.
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Silva, Gleison Elias da. "Implementação e caracterização da resposta dinâmica de transdutores de deformação e temperatura a fibras ópticas baseados em redes de Bragg." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-12122011-140541/.
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Essa dissertação de mestrado é dedicada ao estudo, desenvolvimento e caracterização da resposta dinâmica de transdutores de deformação mecânica e de temperatura baseados em grades de Bragg inscritas em fibras ópticas (FBG). Como não se encontram referências diretas na literatura da área sobre a caracterização da resposta dinâmica de sensores de temperatura e deformação a FBG, percebeu-se a importância de realizar um trabalho com ênfase nesse aspecto. O desenvolvimento de transdutores FBG de deformação e de temperatura com resposta dinâmica rápida é de grande importância, já que as grades de Bragg são afetadas, de maneira intrínseca, simultaneamente pelas duas grandezas e que existe um amplo leque de aplicações em que uma delas, ou ambas, variam rapidamente. Nesses casos, diferenças em termos de tempos de resposta entre os sensores utilizados para medição de deformação e os usados para compensação de temperatura podem acarretar em erros significativos nas medidas, o que pode até inviabilizar o uso dos sensores a grades de Bragg em tais aplicações. Este trabalho apresenta um compêndio da teoria da tecnologia das FBG para aplicação em sensores ópticos de deformação e de temperatura. Buscando contribuir para o domínio das técnicas de fabricação de sensores a FBG no Brasil, também são apresentados os resultados experimentais da utilização de grades de Bragg inscritas em fibras ópticas fabricadas no laboratório da Subdivisão de Sensores (EFO-S), da Divisão de Fotônica do Instituto de Estudos Avançados (IEAv) do Comando-Geral de Tecnologia Aeroespacial (CTA), como elementos sensores em ensaios de deformação e de temperatura. Os resultados de caracterizações, tanto de FBG produzidas no IEAv quanto de sensores de deformação e de temperatura comerciais das empresas Micron Optics e Fiber Sensing, foram obtidos por meio de três interrogadores diferentes e são comparados e apresentados neste trabalho. Em uma análise realizada dos resultados apresentados de sensores a FBG, utilizados para medição de temperatura e de deformação mecânica em alguns arranjos experimentais, foram observados comportamentos dinâmicos não lineares que apresentam-se como um obstáculos a serem vencidos para a viabilização da aplicação desta técnica à medição desses parâmetros quando os mesmos são rapidamente variáveis.This dissertation is devoted to the study, development and characterization of the dynamic response of mechanical strain and temperature transducers based on Bragg gratings inscribed in optical fibers (FBG). Since there are no direct references in the literature on the characterization of the dynamic response of FBG based temperature and strain sensors, it was realized the importance of conducting a study with emphasis on this aspect. The development of FBG strain and temperature transducers with fast dynamic response is of great importance, since the Bragg gratings are intrinsically and simultaneously affected by the two quantities and there is a wide range of applications in which one or both quantities vary rapidly. In such cases, differences in response times between the sensors used for measurement of strain and used for temperature compensation can result in significant errors, which may even preclude the use of FBG sensors in such applications. This work presents a compendium of the theory related to FBG technology for application in optical strain and temperature sensors. Seeking to master the techniques of manufacture of the FBG sensors in Brazil, experimental results from the use of FBG manufactured in the laboratory of Sensors Subdivision (EFO-S), of Photonics Division of Institute of Advanced Studies (IEAv) of General Command for Aerospace Technology (CTA) as sensor elements in strain and temperature trials are also presented. The results of both characterizations, of FBG produced in IEAv and strain and temperature commercial sensors, produced by Micron Optics and Fiber Sensing manufacturers, were obtained from three different interrogators and are compared and presented in this paper. In an analysis of the results of FBG sensors used for measuring temperature and mechanical deformation in some experimental arrangements, nonlinear dynamic behaviors were observed. Such behaviors present themselves as an obstacle to be overcome to achieve the feasibility of applying this technique to measurement of these parameters when they are rapidly changing.
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Gonçalves, Leonardo Correia. "Configuração interferómetrica diferencial para medição de deformação e temperatura." Master's thesis, Universidade da Madeira, 2010. http://hdl.handle.net/10400.13/248.
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Este documento descreve a implementação de um sistema interferométrico diferencial para a interrogação de redes de Bragg com o objectivo da medição diferencial de deformação e temperatura. Foram implementados dois sistemas de interrogação, um utiliza uma configuração implementada através de instrumentação física, e outro, uma configuração implementada através de instrumentação virtual, desenvolvida com recurso ao ambiente LabVIEW®. O esquema diferencial permite diminuir os efeitos de sensibilidade cruzada indissociáveis a estes sistemas.
Foram realizados testes de deformação e temperatura de forma a validar o funcionamento do sistema virtual. Em ambos os casos, os resultados foram próximos dos obtidos com o sistema convencional, verificando-se que a instrumentação virtual é uma forma de aproveitar as vantagens que este esquema de interrogação apresenta: grande sensibilidade e elevada gama dinâmica, e permite reduzir uma de suas desvantagens, o elevado custo.
Verificou-se ainda a viabilidade da aplicação da configuração estudada num sistema de análise térmica diferencial para identificação de compostos em amostras desconhecidas. O sistema foi demonstrado utilizando uma mistura de acetona e metanol.
Do trabalho realizado nesta dissertação foi possível efectuar algumas publicações que foram submetidas em Revistas e Conferências Científicas. A primeira ao Symposium On Enabling Optical Networks and Sensors SEON - 2010, Anexo A. A segunda à 21st International Conference on Optical Sensors - OFS 2011, Anexo B. E uma terceira submetida à revista Journal of Lightwave Technology, Anexo C.José Manuel Rocha Teixeira Baptista e Pedro Alberto da Silva Jorge
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Dejdar, Petr. "Grafické uživatelské rozhraní pro senzorické systémy." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377158.
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Master thesis is focused on creating graphical user interface for the sensorical system based on Phase-OTDR. Theoretical part describes optical fibers, explains the principle of Bragg gratings, their production and their use in sensors. Methods of optical fiber attenuation and phase OTDR measurement are also described. Other part is focused on LabVIEW programming software and utilization of sensorical system and its components. Practical part deals with the user interface itself, which consists of two tabs. The first tab is designed for evaluation and display of measured data. The second tab is used to control and set up system components. Both of these tabs are further subdivided into other subtabs. Regarding the conclusion, further development of the program and options of hardware replacement for improving this sensorical system in the future will be discussed.
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Helán, Radek. "Modelování a optimalizace komplexních vláknových difrakčních struktur." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233450.
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The thesis discusses the fiber Bragg gratings simulations, analysis and design. In the present time, there are several methods to simulate fiber gratings response based on the stated parameters that define their dimensions and material features. However, this work deals with a different issue, that is the synthesis of the input parameters for demanded spectral responses. The main aim of the work is to achieve a synthesis method that would help to discover parameters describing advanced grating structure, based on the required spectral reflectivity. The basic demand for the parameter synthesis is an achievement of the real values in terms of the consequent production of the suggested structure. The described synthesis method considers advanced fiber grating structure as a structure of several uniform grating sections. The input parameters are estimated in steps, using the well-known direct methods in order to obtain grating responses and feedback to establish the parameters changes. The principle methods involve establishment of initial input parameter values and necessary subsequent algorithm leading to optimize the required spectral response. The initial values are calculated by a simplified model based on the coupled theory equations that are handled for the periodic disturbances in cylindrical waveguide. The following optimization uses the multiple thin film stack and transfer matrix methods. The properties of grating structure spectral reflectivity are step by step calculated while using these direct methods. Input parameters are established in the next several steps. Establishment of input parameters is done subsequently, based on the demanded and calculated output spectral reflectivity properties. Optimizing process is limited by possibilities of the grating manufacture technology. It is possible to assemble arbitrary fiber grating structure taking in term the demanded spectral response. Nevertheless, the calculated input parameters are real for the following manufacture. This method could be used to design optical band stop filter, high-pass and low-pass filters or filters for special applications.
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Nefissi, Naoufel. "Modélisation et mesure des efforts axiaux le long d'une fixations montées avec interférence. Application aux structures aéronautiques." Thesis, Toulouse, INSA, 2012. http://www.theses.fr/2012ISAT0042/document.
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Les assemblages à base de fixations montées avec interférence et prétension sont largement utilisés dans le domaine de la construction aéronautique, notamment dans les zones structurales fortement chargées et soumises à des sollicitations de fatigue. Les performances de ces assemblages sont sensibles à de nombreux paramètres liés à la géométrie et aux matériaux mis en jeu. Pour optimiser la qualité de ces liaisons et atteindre les gains de durée de vie attendus, il est important de disposer de modèles à la fois rapides et fiables qui permettent, dès la phase de conception, d’évaluer l’influence des paramètres d’entrée sur les efforts caractéristiques de l’assemblage. Les travaux s’attachent, dans un premier temps, en s’appuyant sur une modélisation par éléments finis très détaillée du processus d’assemblage, à bien identifier les phénomènes mécaniques les plus caractéristiques des liaisons étudiées. Une approche analytique de premier niveau est ensuite développée. Elle conduit à un modèle d’estimation des efforts et de contraintes présentes dans les pièces assemblées qui produit des résultats très voisins de ceux obtenus avec le modèle de référence. Un modèle numérique dédié,basé sur des éléments finis axisymétriques et codé sous Matlab, est ensuite proposé. Il est apte à évaluer l’influence des variations des paramètres le long de l’interface entre les pièces tout en considérant les effets de bords. Une étude expérimentale basée sur une instrumentation de l’assemblage avec des fibres optiques à réseaux de Bragg est présentée. Les corrélations entre les résultats expérimentaux et ceux issus des modélisations sont très satisfaisantesAssemblies based on interference fit fastener and preload are widely used in the fieldof aircraft construction, especially on structures heavily loaded and subjected to fatigue stresses.The performances of these assemblies are sensitive to many parameters related to the geometry and to the constitutive materials. To improve the quality of these assemblies and achieve the assembled parts. This simple model produces results very similar to those obtained with thereference model. A dedicated numerical model, based on axisymmetric finite elements and developed using Matlab code, is also proposed. It is able to evaluate the influence of parameter variations along the interface between the parts while considering the side effects. An experimental study based on an assembly instrumented with Fiber Bragg Gratings is presented.The correlations between the experimental results and those from the models are very satisfactory lifetime gains expected, it is important to use, from the early design phase, fast and reliable models in order to evaluate the influence of input parameters on the most significant efforts that take place around the fastener. In a preliminary phase, the work focuses on clearly identifyingthe mechanical phenomena characterizing the behavior of the mechanical connections understudy, using a very detailed finite element reference model of the assembly process. An analytical approach is then developed. It leads to a first level model for estimating loads and stresses in the assembled parts. This simple model produces results very similar to those obtained with the reference model. A dedicated numerical model, based on axisymmetric finite elements and developed using Matlab code, is also proposed. It is able to evaluate the influence of parameter variations along the interface between the parts while considering the side effects. An experimental study based on an assembly instrumented with Fiber Bragg Gratings is presented.The correlations between the experimental results and those from the models are very satisfactory
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Lyöri, V. (Veijo). "Structural monitoring with fibre-optic sensors using the pulsed time-of-flight method and other measurement techniques." Doctoral thesis, University of Oulu, 2007. http://urn.fi/urn:isbn:9789514287022.
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Abstract
This thesis deals with the developing of fibre-optic instruments for monitoring the health of civil engineering and composite structures. A number of sensors have been tested for use with different road structures, concrete bridges, fibre reinforced polymer (FRP) containers and other composite specimens, the interrogation methods being mainly based on measuring optical power and time-of-flight (TOF). The main focus is on the development of a fibre-optic TOF measurement system and its applications, but different sensing needs and fibre-optic measurement systems are also reviewed, with the emphasis on commercial devices.
Deformation in a road structure was studied with microbending sensors of gauge-length about 10 cm and a commercial optical time domain reflectometer (OTDR) in a quasi-distributed fashion. The responses of the optical fibre sensors during the one-year measurement period were similar in shape to those obtained with commercial strain gauges but the absolute measurement values typically deviated by several tens of per cent. Low dynamic range, crosstalk and poor signal-to-noise ratio proved to be the main problem when measuring several successive sensors with an OTDR. In another road investigation, microbending and speckle sensors were found useful for providing on/off-type information for traffic control applications.
FRP composite containers were investigated with the focus on developing a continuous monitoring system for improving yield and quality by evaluating the state of cure during the manufacturing process and for assessing damage, e.g. delaminations, during service life. Standard multi-mode and single mode fibres with a typical length of a few hundreds of metres were embedded inside the walls of containers during the normal manufacturing process, and the measurements were carried out using an optical through-power technique and an OTDR. This largely empirical investigation revealed that the coating material and its thickness have an effect on loading sensitivity and on the applicability of the method for cure monitoring. The measurement data also indicated that the end-of-curing process and the location of external damage can be determined with a distributed optical fibre sensor and an OTDR.
Several versions of a pulsed time-of-flight measurement system were developed for interrogating sensor arrays consisting of multiple long gauge-length sensors. The early versions based on commercial electronics were capable of producing relevant measurement data with a reasonable precision, but they suffered especially from poor spatial resolution, low sampling rate and long-term drift.
The high precision TOF system developed in this thesis is capable of measuring time delays between a number of wideband reflectors, such as connectors or fibre Bragg gratings (FBG), along a fibre path with a precision of about 280 fs (rms-value) and a spatial resolution of about 3 ns (0.30 m) in a measurement time of 25 milliseconds. By using a fibre loop sensor with a reference fibre, a strain precision below 1 με and a measurement frequency of 4 Hz can be achieved. The system has proved comparable in performance to a commercial FBG interrogation system in monitoring the behaviour of a bridge deck, while the fact that it allows static and dynamic measurements with a number of long gauge-length sensors, also embedded in FRP composite material, makes this TOF device unique relative to other measurement systems.
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Fedin, Igor. "Peculiarities of the Thermo-Optic Coefficient at High Temperatures in Fibers Containing Bragg Gratings." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1309207081.
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Prášil, Jiří. "Metody řešení vlivu optické disperze na stávajících optických sítích." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218200.
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This diploma thesis deals with analysis of current diagnostic methods of optical networks, and it is focused on optical fiber dispersion in singlemode fibers. The work starts with a describtion chromatic dispersion and polarization mode dispersion, causes of and thein influence on the transmitted signal at the beginning. There are set out principles and their appropriate use in the list of measuring methods. Furthermore, the work are given the current possibilities for compensation above dispersions. The sixth chapter deals with the measurements and simulations of real routes in the OptiSystem. There are given appropriate compensation methods for the selected route speeds in the last chapter. The simulation is performed for the bit rate 2.5 Gbit / s, 10 Gbit / s and 40 Gbit / s.
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Triollet, Sébastien. "Développement d’un capteur à fibre optique à base de réseaux de Bragg superposés de courtes et de longues périodes : application à la mesure discriminée de température et de déformation." Thesis, Saint-Etienne, 2010. http://www.theses.fr/2010STET4018/document.
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[Les capteurs à fibres optiques présentent des qualités intéressantes en termes de tailles et de poids relativement faibles qui permettent de réduire l'intrusivité du capteur dans le matériau (ou dans la structure composite). Ils sont également insensibles aux perturbations électromagnétiques, stables et durables dans le temps, mais aussi sensibles à plusieurs sollicitations comme la température, la déformation et la pression, d'où un besoin essentiel de les discriminer. Parmi eux on distingue les réseaux de Bragg : ceux à courtes périodes (FBG : Fiber Bragg Grating) et ceux à longues périodes (LPG : Long Period Grating). Le travail de thèse reporté dans ce manuscrit, traite du développement d'un capteur à fibre optique basé sur la superposition d'un LPG et d'un FBG afin de mesurer et de discriminer la température et la déformation. De nombreuses approches sont proposées dans la littérature afin de découpler ces deux sollicitations cependant elles ne permettent pas forcément une utilisation en conditions réelles de mesures. C'est pourquoi nous introduisons la notion d'efficacité de découplage avec le paramètre E qui permet de comparer toutes ces approches et met en évidence un très bon potentiel pour la structure à base de réseaux superposés LPG/FBG. La mise en œuvre d'un tel composant est décrite dans ce manuscrit et consiste à inscrire initialement le LPG puis le FBG au même endroit et sur toute la longueur du LPG. De plus ce type de structure permet un multiplexage qui, bien que faible, est néanmoins possible. Les étalonnages en température et en déformation du capteur ont permis de mettre en évidence une erreur de l'ordre de 2% sur la sensibilité à la température et de 3% sur la sensibilité à la déformation, ce qui conduit à une erreur sur l'estimation de la température et de la déformation mesurée de l'ordre de 0.3°C et 3 microdef. Dans un souci applicatif, le capteur à base de réseaux de Bragg superposés est tout d'abord utilisé pour instrumenter une structure métallique soumise simultanément à une variation de température et de déformation. Les valeurs mesurées présentent une incertitude maximale de 0.4°C pour la température et de 3 me pour la déformation ce qui permet de valider notre composant pour le contrôle et la surveillance de structures métalliques. La seconde application étudiée est relative à l'instrumentation de pièces composites stratifiées de type verre/époxy pour le suivi de procédés d'élaboration par voie liquide : VARTM (Vacuum Assisted Resin Transfer Molding) et LRI (Liquid Resin Infusion), pour lesquels l'évolution de la température et de la déformation au cours du procédé est suivie par le capteur à base de réseaux de Bragg superposés LPG/FBG. Des mesures diélectriques (DEA) sont également réalisées au cours de ces procédés et permettent la comparaison et la validation de nos résultats][Optical Fibre Sensors present some interesting qualities when considering its size and weight relatively light, which lead to a low intrusivity of the sensor in a material (a composite structure). These sensors are insensitive to electromagnetic phenomenon, stable and long lasting with time, but sensitive to several solicitations such as temperature, strain and pressure hence a real need of discrimination. Among these sensors, we may discern the Bragg gratings: the Long Period Grating one (LPG) and the Fibre Bragg Grating (FBG) one. This thesis work reports the development of an optical fibre sensor based on two superimposed Bragg gratings: LPG and FBG for measuring and discriminating temperature and strain. Several studies are reported in literature without getting a real condition use. That's why we propose a parameter E, which stand for the discrimination efficiency leading to a possible comparison of the existing techniques and highlight the quite good potential of superimposed Bragg gratings. The settings of such a structure are given in this thesis report and consist in writing LPG first, then FBG over the entire length of the LPG, which also gives multiplexing possibilities. Strain and temperature calibration steps give sensitivities errors of 2% for temperature and 3% for strain, which lead to estimated errors on measured strain and temperature of 0.3°C and 3 microstrain respectively. In an application point of view, the sensor has been used for the instrumentation of a metallic structure subjected to a variation of temperature and strain applied simultaneously. The results exhibit a maximum error of 0.4°C and 3me for temperature and strain respectively, which is a good validation of the sensor for structural control and monitoring purpose. The second studied application is about instrumentation of glass/epoxy composite specimen for monitoring manufacturing processes: VARTM (Vacuum Assisted Resin Transfer Moulding) and LRI (Liquid Resin Infusion), for which temperature and strain have been monitored with the superimposed Bragg gratings based sensor. Dielectric analyses have also been performed during those processes in order to compare and validate our results]
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Sans, Canovas Daniel. "Advances in fibre Bragg grating sensors for damage detection in composite laminates: application in quasi-static and fatigue delamination tests." Doctoral thesis, Universitat de Girona, 2013. http://hdl.handle.net/10803/117357.
Full textAbstract:
The use of composite materials in industrial applications such as aeronautical, aerospace or wind energy production has greatly increased in recent decades. Due to their inherent properties, these materials allow lighter, larger and more resistant structures. However, the use of composite materials for components or structures with highly stringent requirements, is hampered by the lack of knowledge of their reliability. In this thesis, some fundamental aspects about the use of fibre Bragg grating (FBG) sensors for internal strain measurements in composite laminates are discussed. In addition, a highly accurate method for locating the crack tip position in mixed-mode delamination growth has been presented. Finally, an experimental application of FBGs to dynamic measurements in mode I fatigue test has been performedL’ús de materials compostos en aplicacions de caràcter industrial com per exemple l’aeronàutica, aeroespacial o la de producció d’energia eòlica, ha crescut exponencialment durant les últimes dècades. Degut a les seves extraordinàries propietats, l’ús d’aquests materials permet la construcció d’estructures més lleugeres, grans i resistents, tot i que el seu ús en components d’alta responsabilitat estructural està limitat per la manca de coneixement en relació a la seva fiabilitat estructural. En aquesta tesi es discuteixen alguns aspectes significants sobre l’ús de FBGs per a mesurar camps de deformació en l’interior de laminats de material compòsit, s’ha analitzat també la capacitat de localització de la punta d’una esquerda en creixement de mode mixt i per últim s’ha desenvolupat una aplicació pràctica dels FBG en temps real en assaigs a fatiga en mode I
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Triollet, Sébastien. "Développement d'un capteur à fibre optique à base de réseaux de Bragg superposés de courtes et de longues périodes : application à la mesure discriminée de température et de déformation." Phd thesis, Université Jean Monnet - Saint-Etienne, 2010. http://tel.archives-ouvertes.fr/tel-00688229.
Full textAbstract:
[Les capteurs à fibres optiques présentent des qualités intéressantes en termes de tailles et de poids relativement faibles qui permettent de réduire l'intrusivité du capteur dans le matériau (ou dans la structure composite). Ils sont également insensibles aux perturbations électromagnétiques, stables et durables dans le temps, mais aussi sensibles à plusieurs sollicitations comme la température, la déformation et la pression, d'où un besoin essentiel de les discriminer. Parmi eux on distingue les réseaux de Bragg : ceux à courtes périodes (FBG : Fiber Bragg Grating) et ceux à longues périodes (LPG : Long Period Grating). Le travail de thèse reporté dans ce manuscrit, traite du développement d'un capteur à fibre optique basé sur la superposition d'un LPG et d'un FBG afin de mesurer et de discriminer la température et la déformation. De nombreuses approches sont proposées dans la littérature afin de découpler ces deux sollicitations cependant elles ne permettent pas forcément une utilisation en conditions réelles de mesures. C'est pourquoi nous introduisons la notion d'efficacité de découplage avec le paramètre E qui permet de comparer toutes ces approches et met en évidence un très bon potentiel pour la structure à base de réseaux superposés LPG/FBG. La mise en œuvre d'un tel composant est décrite dans ce manuscrit et consiste à inscrire initialement le LPG puis le FBG au même endroit et sur toute la longueur du LPG. De plus ce type de structure permet un multiplexage qui, bien que faible, est néanmoins possible. Les étalonnages en température et en déformation du capteur ont permis de mettre en évidence une erreur de l'ordre de 2% sur la sensibilité à la température et de 3% sur la sensibilité à la déformation, ce qui conduit à une erreur sur l'estimation de la température et de la déformation mesurée de l'ordre de 0.3°C et 3 microdef. Dans un souci applicatif, le capteur à base de réseaux de Bragg superposés est tout d'abord utilisé pour instrumenter une structure métallique soumise simultanément à une variation de température et de déformation. Les valeurs mesurées présentent une incertitude maximale de 0.4°C pour la température et de 3 me pour la déformation ce qui permet de valider notre composant pour le contrôle et la surveillance de structures métalliques. La seconde application étudiée est relative à l'instrumentation de pièces composites stratifiées de type verre/époxy pour le suivi de procédés d'élaboration par voie liquide : VARTM (Vacuum Assisted Resin Transfer Molding) et LRI (Liquid Resin Infusion), pour lesquels l'évolution de la température et de la déformation au cours du procédé est suivie par le capteur à base de réseaux de Bragg superposés LPG/FBG. Des mesures diélectriques (DEA) sont également réalisées au cours de ces procédés et permettent la comparaison et la validation de nos résultats]
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Rodriguez, Alexander John, and alex73@bigpond net au. "Experimental Analysis of Disc Thickness Variation Development in Motor Vehicle Brakes." RMIT University. Aerospace, Mechanical and Manufacturing Engineering, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20070209.123739.
Full textAbstract:
Over the past decade vehicle judder caused by Disc Thickness Variation (DTV) has become of major concern to automobile manufacturers worldwide. Judder is usually perceived by the driver as minor to severe vibrations transferred through the chassis during braking [1-9]. In this research, DTV is investigated via the use of a Smart Brake Pad (SBP). The SBP is a tool that will enable engineers to better understand the processes which occur in the harsh and confined environment that exists between the brake pad and disc whilst braking. It is also a tool that will enable engineers to better understand the causes of DTV and stick-slip the initiators of low and high frequency vibration in motor vehicle brakes. Furthermore, the technology can equally be used to solve many other still remaining mysteries in automotive, aerospace, rail or anywhere where two surfaces may come in contact. The SBP consists of sensors embedded into an automotive brake pad enabling it to measure pressure between the brake pad and disc whilst braking. The two sensor technologies investigated were Thick Film (TF) and Fibre Optic (FO) technologies. Each type was tested individually using a Material Testing System (MTS) at room and elevated temperatures. The chosen SBP was then successfully tested in simulated driving conditions. A preliminary mathematical model was developed and tested for the TF sensor and a novel Finite Element Analysis (FEA) model for the FO sensor. A new method called the Total Expected Error (TEE) method was also developed to simplify the sensor specification process to ensure consistent comparisons are made between sensors. Most importantly, our achievement will lead to improved comfort levels for the motorist.