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Bulur, Hatice Gonca. "Determination Of Buried Circular Cylinder With Ground Penetrating Radar Using An Optical Fiber Sensor." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613702/index.pdf.
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The terms &lsquoground-probing radar&rsquo
, &lsquo
ground penetrating radar (GPR)&rsquo
, &lsquo
sub-surface radar&rsquo
or &lsquo
surface-penetrating radar (SPR)&rsquo
refer to various techniques for detecting and imaging of subsurface objects. Among those terms GPR is preferred and used more often. In this thesis, the depth and the position of the buried circular cylinder are determined by a GPR system which comprises of an optical fiber sensor (OFS). The system is a combination of OFS, GPR and optical communication link. In order to determine the depth and the position, first of all the electric field distribution at the OFS is obtained by integrating the Green&rsquo
s function over the induced current distribution. Those distributions are observed for different frequency and depth values. The voltages inside the distribution are measured by OFS. By changing the depth of the cylinder and the frequency of the system, various plots showing x axis displacement versus measured voltages are obtained. Those plots are related to interference fringe patterns. The position and the depth of the cylinder are obtained using interference fringe patterns. All of the studies mentioned are performed in MATLAB R2007b program. The noises of the system due to OFS are extracted using OPTIWAVE OPTISYSTEM 7.0 program. By adding those noises to the measured voltage values, the operating frequency of the system is observed.
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Ali, Alvarez Shamyr Sadat. "Capteurs de corrosion à fibre optique pour la surveillance répartie d’ouvrages en béton armé." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI042.
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La corrosion des armatures de renforcement des structures en béton représente un enjeu socio-économique majeur. Sa détection et le suivi de son évolution constituent un défi pour la recherche appliquée. Les techniques standards non destructives de détection de corrosion mettent en œuvre des procédés indirects tels la mesure d’impédance, de potentiels, ou par ultrasons. Leurs capacités d’auscultation sont limitées dans l’espace (notamment en profondeur), leur coût reste élevé dans un contexte de maintenance périodique et elles conduisent à des paramètres d’interprétation complexe. Des progrès sont nécessaires dans la détection et l’analyse fiable de la progression des processus de corrosion. Dans ce travail, nous présentons une nouvelle méthode pour détecter la corrosion et le suivi de son évolution, basée sur l’observation directe des changements intervenant à l’interface fer-béton par Capteur à Fibre Optique (CFO). L'attaque par corrosion de la surface de l'armature dépend de plusieurs paramètres électrochimiques (température, pH, carbonatation, présence de chlorures, contamination biologique, etc.). Deux comportements mécaniques à l'interface fer-béton sont distingués. Dans le premier cas (carbonatation), le produit d'oxydation du métal reste à l'interface et augmente la pression interne, pouvant conduire à la fissuration de la couche de béton extérieure. Dans le second cas (piqures), les ions métalliques sont évacués hors de la structure avec comme conséquence une réduction de section des barres d'armature (affaiblissement du renforcement). Un CFO innovant est proposé dans le but de localiser et quantifier les deux types de corrosion précités. Le principe consiste à observer l’impact direct de la corrosion sur l’état de déformation d’une fibre optique préalablement précontrainte par construction. Deux procédés métrologiques sont étudiés : Bragg et réflectométrie fréquentielle (Optical Frequency-Domain Reflectometry - OFDR). Des tests de corrosion accélérée montrent la faisabilité du procédé. Une procédure de fabrication simplifiée et à coût optimisé est proposée pour la surveillance in situ et répartie des structures de génie civil, dans une perspective future de maintenance conditionnéeCorrosion of reinforced bars (rebars) in concrete structures remains a major issue in civil engineering works, being its detection and evolution a challenge for the applied research. Usual non-destructive corrosion detection methods involve impedance, potential or ultra-sonic indirect measurements of complex interpretation. Besides, they are restricted to near-surface examinations and the maintenance cost is still high (scheduled maintenance). Many efforts remain to be done to survey the onset and progression of corrosion processes in a reliable way. In this work, we present a new methodology to detect the onset of corrosion and to monitor its evolution, based on the direct observation of rebar–concrete interface changes by the use of an Optical Fiber Sensor (OFS). The corrosion attack over rebar surface depends on several physical, chemical and electrochemical parameters (temperature, pH, presence of chlorides/CO2, biological contamination, etc.). Two types of mechanical behavior and described. In the first case (carbonation), metal oxidation products stay at the interface and increase internal pressure, potentially leading to a crack of the external concrete layer. In the second case (pitting), metal ions are evacuated out of the structure, leading to a reduction of the rebar section (structural weakness). An innovative sensor design is proposed with the purpose of localizing and quantifying the amount of both corrosion types. The basic principle consists in measuring the impact of corrosion over the state of strain of a prestressed optical fiber. Two metrological techniques are used: Fiber Bragg Grating (FBG) and Optical Frequency-Domain Reflectometry (OFDR). Accelerated corrosion tests were performed in electrolytic solutions for both kinds of corrosion types (pitting and carbonation) and provide a proof-of-concept for the technique. A low-cost, simplified manufacturing procedure is proposed with the aim to provide distributed and in situ Structural Health Monitoring (SHM), suitable for future Condition-Based Maintenance (CBM) of civil engineering concrete structures
3
Waris, Marc. "Mise en œuvre, instrumentation, validation et modélisation d’un système d’injection RTM pour la fabrication de structures composites de hautes performances." Thesis, Saint-Etienne, EMSE, 2012. http://www.theses.fr/2012EMSE0661/document.
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Les matériaux composites ont connu ces dernières années une forte croissance, croissance aujourd'hui renforcée par les nouvelles normes européenne visant à diminuer les émissions CO2 d'ici 2020. La réalisation de pièces complexes peut poser de nombreuses problématiques de fabrication comme la formation de zones sèches, ou la création de distorsions géométriques. Les origines de ces problématiques sont souvent liées à un manque de connaissance et de maîtrise des phases d'imprégnation des renforts et de cuisson du matériau. L'amélioration de la robustesse des procédés nécessite d'avoir une connaissance fine des phénomènes physiques qui ont lieu lors de l'élaboration. Dans cette perspective, les procédés d'élaboration de matériaux composites ont été étudiés à travers la mise en place d'un démonstrateur de laboratoire dans le cadre du projet LCM Smart. Ce pilote d'injection a permis de valider des solutions d'instrumentation, à partir de capteurs innovants (OFS) développés en partenariat avec le laboratoire d'optique Hubert Curien.L'application de cette instrumentation dans le cadre du suivi du procédé RTM a démontré les capacités des OFS pour le suivi des caractéristiques physiques de la pièce (le front d'écoulement, la température, les déformations résiduelles et le degré de cuisson). La comparaison des caractéristiques mesurées avec des simulations numériques effectuées en collaboration avec ESI, a montré une bonne corrélation.Enfin, l'instrumentation a permis de mettre en évidence l’intérêt d’un outillage composite en HexTool pour la réduction des contraintes résiduelles liées à l'interaction outil/pièceA significant growth in production and consumption of composite materials can be seen recently; growth reinforced by the new European standards, aimed at reducing CO2 emissions by the year 2020.The producing of complex parts can cause many difficulties for manufacturing because of their geometries and / or their constituents (using of various materials). For example, dry zones or geometric distortion formation. The origins of these difficulties are often related to a lack of knowledge and control of the reinforcement's impregnation phases and material curing.Improving the robustness of the processes demands a detailed knowledge of physical phenomena that occur during the producing. For this, we studied the composite materials production through the implementation of a laboratory demonstrator in the project LCM Smart. This pilot injection was used to validate instrumentation solutions, from innovative sensors (OFS) developed in partnership with the optical laboratory Hubert Curien. The application of this instrumentation in the context of RTM process monitoring in the development of simple parts has demonstrated the capabilities of OFS to control physical characteristics of the part (the flow front, temperature, residual strain and curing degree). The comparison of the measured characteristics with numerical simulations carried out in collaboration with ESI showed a good correlation.Finally, instrumentation has demonstrated the capacity of composite tool made by HexTool to minimize the residual stresses due to the tool/part interaction
4
Allsop, Thomas David Paul. "A fibre optical strain sensor." Thesis, University of Plymouth, 1999. http://hdl.handle.net/10026.1/2779.
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Strain-sensing elements, fabricated in standard communications-grade single mode optical fibre, are increasingly being considered for application in structural health monitoring. The reason for this is the numerous advantages demonstrated by these devices compared with traditional indicators. This thesis describes work carried out on optical sensors at the University of Plymouth. The aim of this work was to achieve an optical fibre strain sensing system capable of measuring absolute strain with good resolution and having wide dynamic range, without bulky optical equipment and not susceptible to misalignment due to handling. Earlier work was devoted to study on an intrinsic Fabry-Perot interferometric sensor and an optical phase-shift detection technique. The sensing element investigated relied on the end face of an optical fibre as one mirror and the second mirror being a layer of Titanium Dioxide (TO2). Although some results are included, it was soon realised that this sensor had a number of problems, particularly with fabrication. As no simple solution presented itself, consideration was given to a sensor that made use of the change in reflectance of an intra-core fibre Bragg grating when the grating was subjected to strain. The bulk of work described in this thesis is concerned with this type of sensing element. The grating structure is inherently flexible and a number of structural formats were studied and investigated. The first and simplest grating considered was two linearly chirped Bragg gratings used in a Fabry-Perot configuration (a grating resonator). The sensor was tested using the sensing detection system and although the fabrication problems were overcome absolute strain measurement was unattainable. To achieve this end, a theoretical study of a number of grating structures was carried out using the T-matrix Formalism. Confidence in using this approach was gained by comparing the spectral behaviour of a proposed grating with results, which were given by another theoretical model for the same proposed grating. The outcome of this study was that two structures in particular showed promise with regard to absolutism (the measure of true strain) and linearity. Discussions held with the department of Applied Physics at Aston University about fabrication resulted in one of the proposed designs being abandoned due to difficulties of fabrication. The second structure showed more promise and fabrication attempts were put in hand. This grating is linearly-chirped with a Top-hat function and a sinusoidal perturbation as a taper function of the refractive index modulation. Experiments were performed, data were acquired and system performance for this sensor is presented. The thesis concludes that using such a fibre Bragg grating as the sensing element of a strain sensing system enables it to measure absolute strain without using bulky optical equipment. At present, the resolution of strain is limited by the quality of the grating being fabricated (anomalies on profile), this should improve once the fabrication technique is refined.
5
Ludden, Brendan Patrick. "A distributed optical fibre sensor." Thesis, University of Cambridge, 1997. https://www.repository.cam.ac.uk/handle/1810/272327.
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Moss, Steven E. "Wavelength division multiplexed optical fibre sensor networks." Thesis, Manchester Metropolitan University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334635.
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MacLean, Alistair. "A distributed fibre optic water sensor." Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248853.
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Laufer, Jan. "Photothermal determination of optical coefficients using an optical fibre sensor." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394370.
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Merchant, David Frank. "Optical fibre fluorimeter for online measurement." Thesis, Liverpool John Moores University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313161.
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Wang, Dong Ning. "White light interferometric sensor systems." Thesis, City University London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283188.
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Liang, Yuanxin. "Respiration monitoring with a fibre optic sensor." Swinburne Research Bank, 2008. http://hdl.handle.net/1959.3/47121.
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Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Atom Physics an Ultra-fast Spectroscopy, 2008.A thesis submitted for the degree of Master of Engineering, Centre for Atom Physics an Ultra-fast Spectroscopy, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2008. Typescript. Bibliography: p. 143-149.
12
Su, Xu. "Design and Evaluation of Off-centered Core Fiber for Gas Sensing." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99348.
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Gas Sensing Has Become a Very Important and Attractive Technique Because of Its Various Applications, Such as in the Increasingly Concerning Case of Environmental Issues, Automobile Emission Detection, Natural Gas Leakage Detection, Etc. It Also Has Significant Applications in Industries, Such as Safety and Health Monitoring in Underground Mines. Among Those Sensing Areas, Fiber-optic Sensors Have Drawn Considerable Attention Because of Its Small Size, Light Weight, High Sensitivity, and Remote Sensing Capability. However, Current Fiber-optic Gas Sensing Techniques Have Several Limitations on Their Potential for Multiplexed or Distributed Sensing Due to Difficulties Such as High Complexity or Large Loss.
To Accomplish the Goal for Multiplexed Gas Sensing, an Off-centered Core Fiber Design Is Investigated. The Eccentric Core Can Reduce Attenuation, Keep Mechanical Strength, and Lower Fabrication Cost. To Verify the Feasibility of the Design, Fiber Field Distribution Is First Studied in Simulation, Which Will Be Discussed in Detail in Chapter 2. Then Two Fiber Samples with a Length of 10 Cm and 40 Cm Are Prepared and Placed in a Custom Methane Sensing System for Gas Absorption Testing, Which Is Detailed in Chapter 3. From Etching Analysis, Localized Surface Defects Are Found as the Main Reason for Power Loss. Performance Such as Detection Resolution and Sensitivity Are Investigated. In Chapter 4, Theoretical Evaluations Have Been Conducted for Multiplexed Sensors Performances Using the Off-centered Core Fiber to Study the Impact Fiber Parameters on Sensing System Design. The Conclusion and Summary Are Presented in Chapter 5.Master of Science
Gas Sensing Has Become a Very Important and Attractive Technique Because of Its Various Applications, Such as in the Increasingly Concerning Case of Environmental Issues, Automobile Emission Detection, Natural Gas Leakage Detection, Etc. It Also Has Significant Applications in Industries, Such as Safety and Health Monitoring in Underground Mines. Among Those Sensing Areas, Fiber-optic Sensors Have Drawn Considerable Attention Because of Its Small Size, Light Weight, High Sensitivity, and Remote Sensing Capability. However, Current Fiber-optic Gas Sensing Techniques Have Several Limitations on Their Potential for Long Distance Distributed Sensing Due to Difficulties Such as High Fabrication Complexity. In This Work, a Fiber-optic Gas Sensor with Special Structure Was Designed. The Sensor Can Reduce Attenuation, Keep Mechanical Strength, and Lower Fabrication Cost. To Verify the Feasibility of the Design, Theory Analysis and Simulation Were Conducted, Which Will Be Discussed in Detail in Chapter 2. Then Two Samples with a Length of 10 Cm and 40 Cm Were Prepared and Placed in a Custom Methane Sensing System for Testing. And Their Performance Such as Sensitivity Is Investigated. In Chapter 4, Theoretical Evaluations Have Been Conducted for Multiplexed Sensors Performances Evaluation to Study the Impact Fiber Parameters on Sensing System Design. The Conclusion and Summary Are Presented in Chapter 5.
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Murtaza, Ghulam. "Dual wavelength referenced intensity modulated optical fibre sensor system." Thesis, Manchester Metropolitan University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358834.
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Glomon, Lhusak. "Source based chromatic methodology for optical fibre sensor systems." Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400231.
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Yang, Yatao. "Development of a distributed optical fibre pH sensor system." Thesis, Glasgow Caledonian University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321322.
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Wong, Yuen Mei. "Optimising the plastic optical fibre evanescent field biofilm sensor." Thesis, Liverpool John Moores University, 2008. http://researchonline.ljmu.ac.uk/5906/.
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This thesis describes the development, characterisation and application of large diameter multimode plastic optical fibre (POF) sensors using evanescent field modulation. The exposed polymethylmethacrylate (PMMA) core of the POF fibre forms the sensor interface that detects refractive index changes of a measurand acting as the cladding. When a liquid measurand is used, the sensor can detect changes in refractive index, absorption and suspended particulates. It is this simple mechanism by which the evanescent field POF sensor operates. The evanescent field POF sensor has been characterised for refractive index of surrounding liquid from 1.33 to 1.49. The sensor demonstrated accuracy of ± 7x 10-3 refractive index units below 1.4 and ±2x 10-3 refractive index units above 1.4. Components have been selected and designed for this project to ruggedise the sensor, to make the sensor more self-contained and cheaper. The original design of the test conditions did not allow for optimum deployment of the sensor as it stripped out the very modes of light that were required for sensing purposes. The system was also operating under pressure, not reflecting the real conditions under which the sensor would be operating. The re-design of test conditions holds the sensor without straining the POF and operates under normal atmospheric pressure. The POF sensor was demonstrated reacting to a real measurand eg biofilm in which initial growth affects the optical properties at the core cladding interface by refractive index modulation. This sensor was capable of measuring biofouling and scaling at water interfaces. The sensor was trialled in a European Commission funded project (CLOOPT) to study biofouling and scaling in closed loop water systems such as heat exchangers in the cooling tower of an electric power plant, and as an interface sensor for water quality monitoring (AQUA-STEW) involving biofilm removal and surface cleansing with a new application for contact lens protein removal systems. Tapering multimode POF was a desirable goal as this increases the proportion of light coupled into the core available for sensing purposes, to achieve a more sensitive evanescent field POF sensor. Optically clear and consistent smooth tapering of ends and mid-lengths of POF fibre were achieved through chemical removal of material. The tapered POF sensor was characterised with a range of refractive indices, and it exhibited two distinct regions; the water/alcohol region below 1.4 refractive index units, and the oil region above 1.4 suggesting the sensor's use as an oil-in-water, or water-in-oil sensor. From 95% confidence limits, the accuracy of the POF was ±O.006 refractive index units (to 2 standard deviations) for fluids of refractive indices above 1.4. Tapered POF is sensitive to refractive index providing a cheap, easy to handle and rugged throwaway sensor for water and beverage process and quality monitoring.
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Hu, Yiqun. "Digital Spatial Domain Multiplexing technique for optical fibre sensor arrays." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245041.
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Zhang, Feng Hong. "A novel optical fibre sensor based on inter-fibre distributed coupling for particle concentration measurement." Thesis, Liverpool John Moores University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361510.
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Wang, Qi. "Studies of multimode fibre linked white light interferometric sensor systems." Thesis, City University London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389649.
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Shen, Yonghang. "Characterization of optical fibre sensor systems for applications at high temperatures." Thesis, City University London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421643.
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Radi, Haidar M. "Frequency hopping spread spectrum multiplexing for interferometric optical fibre sensor networks." Thesis, Manchester Metropolitan University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387483.
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Masoudi, Ali. "Design and application of a distributed optical fibre dynamic strain sensor." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/375125/.
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Over the past two decades, distributed optical fibre sensors (DOFS) based on Brillouin and Raman scattering have been extensively studied. As a result, a wide range of distributed temperature and strain sensors with different sensing range and accuracy levels have been developed. However, due to the weak nature of Brillouin and Raman scattering, most of the research in this field has been focused on DC or quasi-DC measurement of temperature and strain. On the other hand, the Rayleigh-based DOFS which have been previously proposed are only able to detect dynamic disturbances along the sensing fibre. In this thesis, a new sensing technique has been developed which is capable of quantifying and tracking multiple dynamic perturbations along the sensing fibre, simultaneously. The sensing mechanism of the proposed technique relies on the phase of the Rayleigh backscattered light. For any given segment along the fibre, the difference in the phase of the backscattered light radiating from the two ends of that segment changes as a function of the external perturbations at that segment. Therefore, dynamic vibration along the sensing fibre can be extracted by comparing the phase of the backscattered light from two different sections of the sensing fibre. By implementing this technique using an imbalanced Mach-Zehnder Interferometer (IMZI), a distributed sensor was developed that was capable of quantifying dynamic perturbations within the frequency range of 200Hz ~5kHz along a 1km sensing fibre. Furthermore, the same principle was used to develop a distributed magnetic field sensor. By coupling an optical fibre to a magnetostrictive wire and by using this combination as a magnetic field to strain transducer, a distributed magnetic field sensor was formed with magnetic intensity range of 1Gs~ 8Gs and frequency range of 50Hz ~5kHz. In addition, the IMZI arrangement was used as a frequency-to-intensity convertor to develop a distributed dynamic strain sensor based on Brillouin scattering. The proposed sensor exhibited a strain range of 400µέ 4mέ and a sensing range of 2km.
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Liu, Chen. "Advanced optical fibre grating sensors for biochemical applications." Thesis, Bangor University, 2019. https://research.bangor.ac.uk/portal/en/theses/advanced-optical-fibre-grating-sensors-for-biochemical-applications(29757d94-bfe1-4d75-a4db-8563be1a056f).html.
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This thesis describes a detailed study of advanced fibre optic sensors and their applications for label-free biochemical detection. The major contributions presented in this thesis are summarised below. A self-assembly based in-situ layer-by-layer (i-LbL) or multilayer deposition technique has been developed to deposit the 2D material nanosheets on cylindrical fibre devices. This deposition technique is based on the chemical bonding associated with the physical adsorption, securing high-quality 2D materials coating on specific fibre cylindrical surface with strong adhesion as well as a prospective thickness control. Then a " Photonic-nano-bio configuration", which is bioprobes immobilised 2D-(nano)material deposited fibre grating, was built. 2D material overlay provides a remarkable analytical platform for bio-affinity binding interface due to its exceptional optical and biochemical properties. EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide) and NHS (NHydroxysuccinimide) were used to immobilise bioprobes. This kind of configuration is considered to have many advantages such as: enhanced RI sensitivity, enrich immobilisation sites, improved binding efficiency, selective detection. Followed by this configuration, several label-free biosensors were developed. For example, graphene oxide coated dual-peak long period grating (GO-dLPG) based immunosensor has been implemented for ultrasensitive detection of antibody/antigen interaction. The GO-LPG based biosensor has been developed for label-free haemoglobin detection. Apart from biosensors, the black phosphorus (BP) integrated tilted fibre grating (TFG) has been proposed, for the first time, as BP-fibre optic chemical sensor for heavy metal (Pb2+ ions) detection, demonstrating ultrahigh sensitivity, lower limit of detection and wider concentration range. Ultrafast laser micromachining technology has been employed to fabricate long period grating (LPG) and microstructures on optical fibre. The ultrafast laser micromachined polymer optical fibre Bragg grating (POFBG) has been developed for humidity sensing, showing the significant improvement with the reduced response time.
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Lewin, A. C. "An investigation of optical fibre interferometric vibration and rotation measurement techniques." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383750.
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Fouchal, Farid. "Composite cure assessment using spectral analysis (via an embedded optical fibre sensor)." Thesis, De Montfort University, 2001. http://hdl.handle.net/2086/4302.
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Marshall, Raymond Hugh. "A study of optical-fibre electronically-scanned white light interferometric sensor systems." Thesis, City University London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266372.
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Cheevers, Kevin. "Optical Fibre-Based Hydrophone and Critical Ignition in Detonation Cells." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42793.
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This thesis is composed of two distinct parts. The first part of this work addresses the problem of critical ignition behind a decaying shock wave in the context of cellular detonations. Low-pressure (4.1 kPa) shock tube experiments were performed in a thin rectangular channel using the highly-unstable mixture of CH4 + 2O2 and the weakly-unstable mixture of 2H2 + O2 + 7Ar, with Schlieren visualization of the flow field. The dynamics of the lead shock in a detonation cell was reconstructed from measurements of the lead shock position and curvature. The post-shock state and the expansion rate along the path of a Lagrangian particle crossing the lead shock at any given point in the cell cycle were evaluated with the shock jump and shock change equations. The chemical evolution behind the shock was then integrated using a detailed chemistry model. Quenching of the post-shock reaction zone was found within the first half of the detonation cell for both mixtures, with quenching occurring earlier in the highly unstable mixture. Simplified models derived from 1-step and 2-step chemistry models very accurately predict the quenching of the post-shock reactions and the evolution of the ignition delay through the cell.
The second part describes the assembly and characterization of a fibre-optic probe hydrophone (FOPH) for the measurement of shock waves associated with blast-induced neuro-trauma. Compared to traditional polyvinylidene difluoride (PVDF) hydrophones, the assembled FOPH has a higher bandwidth and smaller active diameter, which are comparable to the characteristic time and thickness of shock waves associated with blast-induced neuro-trauma. However, the sensitivity of FOPHs are substantially lower than traditional hydrophones. We assemble a FOPH and provide detailed calculations and measurements of its sensitivity (0.66 mV/MPa) , noise floor, and spatial resolution. The 150 MHz bandwidth, limited by the photodetector, is sufficient for resolving shock waves with over-pressures of up to 174 kPa with 3 measurement points. Experimental measurements of the system noise gives a floor of 260 Pa/√Hz . A detailed noise analysis finds that the system is limited by photodetector noise (215 Pa/√Hz), which is 4x the fundamental shot noise limit, closely followed by a laser noise of 150 Pa/√Hz. We conclude that the system noise floor is insufficient for resolved measurements of the post-shock pressure in the range associated with blast-induced neuro-trauma. From our noise analysis, we quantify the sensitivity enhancement required for resolving this regime, and we conclude that sensitivity-enhancing fibre-coatings could provide a sufficient increase in sensitivity.
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Bashour, Rami. "High voltage optical fibre sensor for use in wire relay electrical protection systems." Thesis, University of Derby, 2016. http://hdl.handle.net/10545/621343.
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The last few decades have a wide spread use of optical fibre sensors in many applications. Optical fibre sensors have significant benefits over existing conventional sensors such as; high immunity to electromagnetic interference, the ability to transmit signal over long distance at high bandwidth, high resolution, usage in hazardous environments and no need for isolation when working at high voltages. The measurement of high voltages is essential for electrical power systems as it is used as a source of electrical information for Relay Protection Systems (RPS) and load management systems. Electrical Power Systems need to be protected from faults. Faults can range from short circuits, voltage dips, surges, transients etc. The Optical High Voltage sensor developed is based on the principle that the Lead Zirconate Titanate (PZT) electrostriction displacement changes when a voltage is applied to it. The displacement causes the fibre (FBG) which is bonded to the PZT material to have a resultant change in the wavelength. An optical fibre sensor prototype has been developed and evaluated that measures up to 250 V DC. Simulation using ANSYS software has been used to demonstrate the operational capability of the sensor up to 300kV AC. This sensor overcomes some of the challenges of conventional sensors issues like electromagnetic interference, signal transmission, resolution etc. R BASHOUR 2 A novel optical fibre high voltage based on the Kerr effect has been demonstrated. The The Kerr effect was determined using Optsim (R-Soft) software and Maxwell software was used to model an optical Kerr Cell. Maxwell software is an electromagnetic/electric field software used for simulating, analysing, designing 2D and 3D electromagnetic materials and devices. It uses highly accurate Finite Element techniques to solve time varying, static, frequency domain electric and electromagnetic fields. A Relay Protection System on electrical networks was discussed in detail. Keywords: Fibre Bragg Grating, Fibre Optics Sensors, Piezoelectricity, Kerr effect, Relay Protection Systems.
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Cusworth, S. D. "An extrinsic optical fibre sensor system for the measurement of pressure and temperature." Thesis, Manchester Metropolitan University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370938.
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Hayes, Simon Antony. "Development of a reinforcing fibre light-guide for use as a damage sensor within composite structures." Thesis, Brunel University, 1995. http://bura.brunel.ac.uk/handle/2438/7119.
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This study presents the results of an investigation to develop a novel sensor which would give a direct indication of the extent of impact damage in a composite. This was achieved by using glass reinforcing fibres to produce a light-guide, which was embedded within a composite laminate. The laminate was then subjected to impact events or bending stresses of sufficient magnitude to cause damage. The impact energies used in this study varied between 2 and 10 Joules, and the indentation depths varied between 0.125 and 1 mm, allowing damage propagation to be monitored. The fall-off in the transmitted light was used to monitor the level of damage, along with C-scanning and sectioning to provide reference data. The use of reinforcing fibres to produce the sensor meant that the strains required to cause failure in the fibres was realistically close to those of the composite constituents. Changes in the transmission characteristics of the sensor were found to correspond to real failure events occurring during impact.
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Zheng, Gang. "Development of advanced birefringent fibre force sensor systems based on frequency modulation continuous wave (FMCW) technology." Thesis, Glasgow Caledonian University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337411.
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DonlagicÌ, Denis. "Microbend sensor structure based on selective excitation and filtering of the modes in graded index optical fibres." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248635.
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Tu, Minh Hieu. "Investigation of metal nanomaterials as a sensing element in LSPR-based optical fibre sensor development." Thesis, City University London, 2014. http://openaccess.city.ac.uk/5919/.
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This thesis aims to explore and demonstrate the potential of using optical fibres both as a waveguide material and a transducer for wide sensing applications, based on a comprehensive review of the localised surface plasmon resonance (LSPR) phenomenon, which occurs at a nanoscale level when light interacts with metallic nanoparticles at a resonance wavelength. The LSPR effect of metallic nanomaterials has shown a strong dependence on the local surrounding environment. A small change for example in the refractive index or in the solution concentration can result in a variation in the LSPR spectrum. Based on this underpinning sensing mechanism, a portable system using an optical fibre coated with gold nanoparticles (AuNPs) as a sensing probe has been developed and tested for the refractive index measurement. Coupled with this, a systematic approach has been developed and applied in this work to optimize the performance of the developed system by considering several key factors, such as the size of nanoparticles produced, pH, coating time and coating temperature. The above optimised probes coated with gold-nanoparticles are further cross-compared with those optimized but coated with gold nanorods with a high aspect ratio. Both types of probes are also prepared for a specific biosensing application based on the antibody-antigen interaction to create wavelength-based sensors for the detection of anti-human IgG. Both probes have exhibited excellent refractive index (RI) sensitivity, showing ~914 nm/RIU (refractive index unit) for the probe coated with gold nanoparticles and ~601 nm/RIU for the one coated with gold nanorods. When using the modified probes for the detection of anti-human IgG, both probes are able to achieve a good LOD (limit of detection) at 1.6 nM. Based on the above cross-comparison, further research has been undertaken to explore the potential of nanoparticles of the alloy of gold and silver, with an aim to combine the robustness of gold and the excellent LSPR effect of silver. To do so, various alloy particles with varied gold/silver ratio and sizes have been prepared and tested for their respective refractive index sensitivities. The probe coated with alloy particles with bigger size and higher silver content has shown better performance in RI sensing. The work has shown a clear relationship between the size of alloys, the content ratio of alloys and RI sensitivity. Research has also been undertaken in this thesis to explore the excellent LSPR effect of hollow nanoparticles resulting from the enhanced coupling between the interior and exterior of the hollow particles. Gold hollow nanocages have been successfully synthesised and tested with different hollowness and a LSPR sensor coated with gold nanocages has shown an excellent sensitivity as high as ~1933 nm/RIU, which is more than 3 times higher than that coated with AuNPs. This result has confirmed that a significant improvement in sensitivity can be made possible for further biosensing as well as chemical sensing applications.
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Azzi, Victor, and Victor Azzi. ""Sensor-in-fibre" optical probes for molecular sensing in the gastrointestinal tract of murine models." Master's thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/37631.
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L’obésité et les maladies cardiométaboliques sont des problèmes de santé publique dans les populations nordiques du Canada ainsi qu’à travers le monde. Il est actuellement proposé que l’augmentation de ces désordres est en partie causée par divers facteurs environnementaux qui génèrent des changements importants du microbiote intestinal. Cette communauté microbienne qui peuple notre tractus gastrointestinal joue un rôle clé dans le métabolisme de nutriments, mais peut aussi avoir des effets néfastes lorsque son équilibre avec l’hôte est perturbé. Cette compréhension a mis en évidence le manque d’outils prédictifs permettant un diagnostic rapide et efficace dans le domaine biomédical. L’analyse actuelle du microbiote est réalisée à posteriori au niveau des selles, ce qui requiert du personnel hautement qualifié de même que des procédures longues et dispendieuses. L’objectif de ce projet est de concevoir un capteur optique qui, une fois implanté dans l’intestin, permettra de détecter en temps réel des biomarqueurs clés produit par le microbiome intestinal. Dans le cadre d’une preuve de concept, une architecture fibrée simple permettant de mesurer quantitativement des variations de pH est démontrée. Contrairement aux capteurs fibrés traditionnels, la sonde optique de ce projet exploite l’onde évanescente générée sur la périphérie de l’interface pour exciter des nanomatériaux greffés dont les propriétés de fluorescence varient selon leur environnement chimique. Les mesures sont possibles grâce à un système optique mobile contrôlé par un logiciel convivial qui permet à un utilisateur nonexpert d’utiliser l’appareil. Les résultats confirment qu’avec un étalonnage préalable il est possible avec cette sonde modèle de prendre des mesures quantitatives du pH en temps réel in vitro. Les expériences préliminaires suggèrent que la sonde permet aussi de mesurer le pH en temps réel dans l’intestin in vivo.L’obésité et les maladies cardiométaboliques sont des problèmes de santé publique dans les populations nordiques du Canada ainsi qu’à travers le monde. Il est actuellement proposé que l’augmentation de ces désordres est en partie causée par divers facteurs environnementaux qui génèrent des changements importants du microbiote intestinal. Cette communauté microbienne qui peuple notre tractus gastrointestinal joue un rôle clé dans le métabolisme de nutriments, mais peut aussi avoir des effets néfastes lorsque son équilibre avec l’hôte est perturbé. Cette compréhension a mis en évidence le manque d’outils prédictifs permettant un diagnostic rapide et efficace dans le domaine biomédical. L’analyse actuelle du microbiote est réalisée à posteriori au niveau des selles, ce qui requiert du personnel hautement qualifié de même que des procédures longues et dispendieuses. L’objectif de ce projet est de concevoir un capteur optique qui, une fois implanté dans l’intestin, permettra de détecter en temps réel des biomarqueurs clés produit par le microbiome intestinal. Dans le cadre d’une preuve de concept, une architecture fibrée simple permettant de mesurer quantitativement des variations de pH est démontrée. Contrairement aux capteurs fibrés traditionnels, la sonde optique de ce projet exploite l’onde évanescente générée sur la périphérie de l’interface pour exciter des nanomatériaux greffés dont les propriétés de fluorescence varient selon leur environnement chimique. Les mesures sont possibles grâce à un système optique mobile contrôlé par un logiciel convivial qui permet à un utilisateur nonexpert d’utiliser l’appareil. Les résultats confirment qu’avec un étalonnage préalable il est possible avec cette sonde modèle de prendre des mesures quantitatives du pH en temps réel in vitro. Les expériences préliminaires suggèrent que la sonde permet aussi de mesurer le pH en temps réel dans l’intestin in vivo.
Obesity and cardiometabolic diseases (CMD) are major public health issues among Canada’s northern population and throughout the world. It is believed that the exponential rise in CMD incidence is due to numerous environmental factors, which are driving important changes in the gut microbiome. This microbial community which populates our intestinal tract plays a key role in nutrient and energy metabolism, but can also drive pathogenic mechanisms when its interaction with the host is disrupted. This understanding has highlighted the lack of predictive tools and biomarkers for rapid and efficient diagnostic of various diseases within the medical field. Current analysis of the gut microbiota is mostly based on sequencing technologies to determine microbial composition and gene expression, while functional analyses are limited to surrogate markers of microbial activities through stool metabolites. The goal of this study is to develop a “Sensor-in-Fibre” probe with the capacity to detect key microbiome-derived molecules relevant to CMD pathogenesis in real time in vivo. The optical probe takes advantage of evanescent fields generated on its peripheral interface to excite species-selective surface-grafted sensing nanomaterials that have varying fluorescent properties based on the target molecules present in the surrounding environment. As a model system, FITC functionalized with (3-aminopropyl)triethoxysilane was grafted on the periphery of an optical fiber, leading to qualitative pH measurements revealed through fluorescence emission qualities. These measurements are possible due to the use of a mobile signal collection apparatus in conjunction with custom software made to enable a non-expert technician to use it. The experimental results demonstrate that, with the appropriate preparation, it is possible to quantitatively measure pH with this probe structure in vitro and preliminary studies suggest that the probe is also capable of measuring pH in vivo in real time.
Obesity and cardiometabolic diseases (CMD) are major public health issues among Canada’s northern population and throughout the world. It is believed that the exponential rise in CMD incidence is due to numerous environmental factors, which are driving important changes in the gut microbiome. This microbial community which populates our intestinal tract plays a key role in nutrient and energy metabolism, but can also drive pathogenic mechanisms when its interaction with the host is disrupted. This understanding has highlighted the lack of predictive tools and biomarkers for rapid and efficient diagnostic of various diseases within the medical field. Current analysis of the gut microbiota is mostly based on sequencing technologies to determine microbial composition and gene expression, while functional analyses are limited to surrogate markers of microbial activities through stool metabolites. The goal of this study is to develop a “Sensor-in-Fibre” probe with the capacity to detect key microbiome-derived molecules relevant to CMD pathogenesis in real time in vivo. The optical probe takes advantage of evanescent fields generated on its peripheral interface to excite species-selective surface-grafted sensing nanomaterials that have varying fluorescent properties based on the target molecules present in the surrounding environment. As a model system, FITC functionalized with (3-aminopropyl)triethoxysilane was grafted on the periphery of an optical fiber, leading to qualitative pH measurements revealed through fluorescence emission qualities. These measurements are possible due to the use of a mobile signal collection apparatus in conjunction with custom software made to enable a non-expert technician to use it. The experimental results demonstrate that, with the appropriate preparation, it is possible to quantitatively measure pH with this probe structure in vitro and preliminary studies suggest that the probe is also capable of measuring pH in vivo in real time.
Résumé en espagnol
Résumé en espagnol
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Sargeant, Ramon Bradley. "A multi-axial optical fibre and linear polarizer based force and torque sensor for dexterous robotic fingertips." Thesis, King's College London (University of London), 2014. http://kclpure.kcl.ac.uk/portal/en/theses/a-multiaxial-optical-fibre-and-linear-polarizer-based-force-and-torque-sensor-for-dexterous-robotic-fingertips(a9c419a3-901e-4a56-9b02-00648539d17e).html.
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As robots play a more pervasive role in our everyday activities more and more research emphasis is being placed on having robots interact directly with humans, whether in terms of taking care of the elderly, medical interventions or performing dangerous or hazardous tasks. Another trend is for robots to use existing human tools to perform desired actions since it is also not always possible or cost effective to design special tools for every robot. This trend has led to the development of anthropomorphic dexterous manipulators that can perform equally or better than the human hand. Thus the accelerating trend is not only to design a dexterous manipulator but to focus on its ability to grasp and manipulate different and sometimes unknown objects. One of the most researched types of grasp is the precision grasp which accounts for over 80 % of the grasps performed by humans on a daily basis. Precision grasps are grasps involving the fingertips and are generally used for tasks that require fine manipulation skills. Fingertip sensors are therefore important for dexterous manipulators since humans can identify salient properties of an object and formulate effective manipulation strategies solely by grasping the object. This PhD project focuses on developing fingertip sensors, specifically force and torque fingertip sensors that can be integrated into the fingertip of an existing dexterous manipulator and gather contact force and torque information during a grasping event. Another goal is to make the sensor magnetic resonant (MR) compatible so that it can be used in high magnetic environments, as in the case of medical, magnetic resonance imagining applications. To accomplish these goals two sensors were developed based on light intensity modulation and novel sensing structures. Optical sensing schemes were chosen because they are not susceptible to magnetic interference, the sensor and its light source can be separated by long distances without significant signal attenuation and the size and weight of the actual sensing element can be reduced since the processing electronics can be positioned far from the sensing structure. The first sensor developed, as part of this PhD work, was a 2-DOF sensor which used a combination of axially-aligned fibres and linear polarizers to modulate the light to measure the applied force and torque respectively. The use of linear polarizers as the main sensing technique for force and torque sensing is a new area of research since linear polarizers have a defined response curve and can be easily cut into any desired shape and size. The experiments conducted with the 2-DOF sensor showed that the linear polarizer response was superior to traditional axially-aligned and reflective techniques and it was tolerant of small deviations and twists in the sensing structure. The second sensor improved on the first sensor by increasing the number of degrees of freedom from two to six by using a parallel-type 3-UPS (Universal Prismatic Spherical) sensing structure to allow measuring six degrees of movement. All of the joints of the sensing structure were made of nitinol flexures to reduce friction and all of the links were made of plastic and bonded together to produce a flexible but light and strong structure. Another improvement was that all of the optical modulation sensors on the sensing structure were based on linear polarizers thereby reducing the possibility of misalignment errors caused by the transmitting and receiving fibres moving out of axial alignment. The new sensor therefore satisfies the design requirements and the experiments conducted showed that Light Intensity Modulation (LIM) using linear polarizers and an appropriate sensing structure can produce an accurate and versatile force and torque sensor.
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Malki, Abdelrafik. "Capteurs de vibrations mécaniques et de pression à fibre optique." Châtenay-Malabry, Ecole centrale de Paris, 1993. http://www.theses.fr/1993ECAP0582.
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L'utilisation des C. F. O. Couvre de plus en plus d'importants domaines de mesures. Cette thèse reprend dans la première partie l'état de l'art des C. F. O. Nous avons, dans la partie expérimentale effectué des mesures sur un capteur de vibration à fibre optique par effet de speckle, et avons montré au cours des expériences de l'amélioration du rapport signal signal sur bruit, dans le cas d'un filtrage spatial entre deux fibres multimodes différentes. La modélisation et la mise au point d'un capteur de vibrations, de type accéléromètre à fibre optique, par modulation d'intensité, fondé sur le micro-usinage de silicium ont été réalisées, ainsi qu'un prototype. Nous avons montré la faisabilité technologique d'un tel capteur. Celui-ci peut-être intégré dans un réseau à multiplexage chromatique. Le travail a consité également en la mise au point des interfaces optoélectroniques. Enfin un capteur de pression par couplage entre deux fibres a fait l'objet d'une étude théorique, et des mesures expérimentales. Grâce à la fusion des deux fibres optiques, on a amélioré la reproductibilité et la robustesse du capteur. Ceci ouvre ainsi la voie sur un grand nombre d'applications dans le domaine des composants optiques, tels que les coupleurs variables.
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Jason, Johan. "Fibre-Optic Displacement and Temperature Sensing Using Coupling Based Intensity Modulation and Polarisation Modulation Techniques." Doctoral thesis, Mittuniversitetet, Avdelningen för elektronikkonstruktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-18964.
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Optical fibre sensors are employed in the measurements of a number of different physical properties or for event detection in safety and security systems. In those environments which suffer from electromagnetic disturbance, in harsh environments where electronics cannot survive and in applications in favour of distributed detection, fibre-optic sensors have found natural areas of use. In some cases they have replaced conventional electronic sensors due to better performance and long-term reliability, but in others they have had less success mainly due to the higher costs which are often involved in fibre-optic sensor systems. Intensity modulated fibre-optic sensors normally require only low-cost monitoring systems principally based on light emitting diodes and photodiodes. The sensor principle itself is very elemental when based on coupling between fibres, and coupling based intensity modulated sensors have been utilised over a long period of time, mainly within displacement and vibration sensing. For distributed sensing based on intensity modulation, optical time domain reflectometer (OTDR) systems with customised sensor cables have been used in the detection of heat, water leakage and hydrocarbon fluid spills. In this thesis, new concepts for intensity modulated fibre-optic sensors based on coupling between fibres are presented, analysed, simulated and experimentally verified. From a low-cost and standard component perspective, alternative designs are proposed and analysed using modulation function simulations and measurements, in order to find an improved performance. Further, the development and installation of a temperature sensor system for industrial process monitoring is presented, involving aspects with regards to design, calibration, multiplexing and fibre network installation. The OTDR is applied as an efficient technique for multiplexing several coupling based sensors, and sensor network installation with blown fibre in microducts is proposed as a flexible and cost-efficient alternative to traditional cabling. As a solution to alignment issues in coupling based sensors, a new displacement sensor configuration based on a fibre to a multicore fibre coupling and an image sensor readout system is proposed. With this concept a high-performance sensor setup with relaxed alignment demands and a large measurement range is realised. The sensor system performance is analysed theoretically with complete system simulations, and an experimental setup is made based on standard fibre and image acquisition components. Simulations of possible error contributions show that the experimental performance limitation is mainly related to differences between the modelled and the real coupled power distribution. An improved power model is suggested and evaluated experimentally, showing that the experimental performance can be improved down towards the theoretical limit of 1 μm. The potential of using filled side-hole fibres and polarisation analysis for point and distributed detection of temperature limits is investigated as a complement to existing fibre-optic heat detection systems. The behaviour and change in birefringence at the liquid/solid phase transition temperature for the filler substance is shown and experimentally determined for side-hole fibres filled with water solutions and a metal alloy, and the results are supported by simulations. A point sensor for on/off temperature detection based on this principle is suggested. Further the principles of distributed detection by measurements of the change in beat length are demonstrated using polarisation OTDR (POTDR) techniques. It is shown that high-resolution techniques are required for the fibres studied, and side-hole fibres designed with lower birefringence are suggested for future studies in relation to the distributed application.Fiberoptiska sensorer används för mätning av ett antal olika fysikaliska parametrar eller för händelsedetektering i larm- och säkerhetssystem. I miljöer med elektromagnetiska störningar, i andra besvärliga miljöer där elektronik inte fungerar samt i tillämpningar där distribuerade sensorer är att föredra, har fiberoptiska lösningar funnit naturliga applikationer. I vissa fall har de ersatt konventionella elektroniska sensorer på grund av bättre prestanda och tillförlitlighet, medan de i andra sammanhang har haft mindre framgång huvudsakligen på grund av den i många fall högre kostnaden för fiberoptiska sensorsystem. Intensitetsmodulerade fiberoptiska sensorer kräver normalt endast billiga utläsningssystem huvudsakligen baserade på lysdioder och fotodioder. Principen för sådana sensorer baserade på koppling mellan fibrer är mycket enkel, och denna typ av sensorer har haft tillämpningar under en lång tid, främst inom mätning av positionsförändring och vibrationer. För distribuerade intensitetsmodulerade sensorer har system baserade på optisk tidsdomän-reflektometer (OTDR) och skräddarsydda sensorkablar funnit tillämpningar i detektion av värme/brand, vattenläckage och kolvätebaserade vätskor. I denna avhandling presenteras, simuleras, testas och utvärderas praktiskt några nya koncept för kopplingsbaserade intensitetsmodulerade fiberoptiska sensorer. Från ett lågkostnads- och standardkomponentperspektiv föreslås och analyseras alternativa lösningar för förbättrad prestanda. Utveckling och installation av en temperatursensor för en industriell tillämpning, innehållande aspekter på sensormultiplexering och nätverksbyggande, behandlas. OTDR-teknik används som en effektiv metod för multiplexering av flera kopplingsbaserade sensorer, och installation av sensornätverk genom användning av blåsfiberteknik och mikrodukter föreslås som ett flexibelt och kostnadseffektivt alternativ till traditionell kabelinstallation. Som en lösning på förekommande upplinjeringsproblem för kopplingsbaserade sensorer, föreslås en ny sensorkonfiguration baserad på koppling mellan en fiber och en multikärnefiber/fiberarray och med ett bildsensorsystem för detektering. Med detta koncept kan ett högpresterande, upplinjeringsfritt sensorsystem med ett stort mätområde åstadkommas. Sensorsystemets prestanda har analyserats teoretiskt med kompletta systemsimuleringar, och en experimentell uppställning baserad på standardfiber och en kamera av standardtyp har gjorts. Simuleringar av möjliga felbidrag visar att systemets experimentella prestanda främst begränsas av skillnader mellan den modellerade och den verkliga optiska effektfördelningen. En förbättrad modell för effektfördelningen föreslås och utvärderas experimentellt. Det visas att prestanda är möjlig att förbättra ner mot den teoretiska gräns på 1 μm som erhållits vid systemsimuleringar. Möjligheterna att använda fyllda hålfibrer och polarisationskänslig mätning för detektering av temperaturgränser studeras i syfte att komplettera befintliga fiberoptiska värmedetektorsystem. Förändringen i fiberns dubbelbrytning vid övergångstemperaturen mellan vätske- och fast fas för ämnet i hålen visas och bestäms experimentellt för hålfibrer fyllda med vattenlösningar respektive en metallegering, och resultaten understöds också av simuleringar. En punktsensor för temperaturdetektering baserad på denna princip föreslås. Vidare visas principerna för distribuerad detektering genom registrering av förändringen i dubbelbrytning med polarisations-OTDR (POTDR). Det visas att OTDR-teknik med hög spatial upplösning behövs för övervakning av de studerade fibrerna, och hålfibrer utformade med lägre dubbelbrytning föreslås för framtida studier av tillämpningen.
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Crosby, Peter. "In-situ cure monitoring of epoxy resin systems." Thesis, Brunel University, 1998. http://bura.brunel.ac.uk/handle/2438/5425.
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This thesis describes the work carried out at Brunel University to develop novel optical fibre sensors capable of monitoring the cure state of an epoxy/amine resin system. The sensors were of simple construction, consisting of an optical fibre from which the silicone cladding layer had been removed over a short length. This stripped length was embedded into the curing resin system. The sensor was successfully used in two ways: i) as an evanescent absorption sensor to monitor specific absorption bands of the resin system. The absorption of energy from the evanescent wave of the optical fibre by absorbing media allows evanescent absorption spectra to be obtained. Absorption spectra were obtained from sensors embedded in a model curing resin system over narrow wavelength ranges. These wavelength ranges corresponded to positions of known absorptions in the spectra of active components in epoxy/amine systems. By monitoring the change in these absorptions it was possible to obtain information about concentration of the amine hardener functional group throughout cure; ii) as a refractive index sensor capable of monitoring the changes in the refractive index of the resin system during cure. A laser diode was used to launch light into the sensor and the intensity of light emerging from the other end of the fibre was monitored. Changes in the resin system refractive index caused changes in the guiding properties of this the sensor. This resulted in a significant change in the intensity of light recorded by the detector and allowed the cure process to be followed. This sensor was also embedded into a unidirectional pre-preg system and was able to follow the cure of the system. The results from the two sensing methods have been compared with data obtained using FTIR spectroscopy and Abbe refractometry during the resin system cure. A theoretical model of sensor response has been developed and compared with the experimental data obtained. The sensor response has also been compared to predictions made by several models of evanescent sensor systems obtained from the literature. These models have been modified so that they can be applied to a sensor embedded into a curing resin system. An analysis of the correspondence between theory and experiment is presented.
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Dias, João Miguel Serras. "Monitorização remota com sensores de fibra ótica." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17319.
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Mestrado em Engenharia FísicaEsta dissertação tem como objetivo a implementação de um sistema de monitorização remota com sensores óticos, nomeadamente sensores em redes de Bragg em fibra ótica. Foi desenvolvido um sistema de monitorização remota, baseado num acelerómetro ótico, que foi implementado no reservatório de água da Universidade de Aveiro, com sensibilidades 87,848 pm/G e 92,351 pm/G nas direções transversal e longitudinal, respetivamente. A estrutura a monitorizar é descrita fisicamente e matematicamente, através de modelos numéricos, com o objetivo de estimar a sua frequência natural segundo a direção longitudinal e transversal. É implementado e descrito um sistema de monitorização remota que consiste na ligação por fibra ótica da estrutura ao sistema central, instalado no Instituto de Telecomunicações – Pólo de Aveiro, o qual é acessível de qualquer local com acesso à internet. Foi também desenvolvido um sensor de nível para futura implementação na mesma estrutura. Estão também descritas e caracterizadas, térmica e mecanicamente, três versões do sensor de nível, que foi sendo otimizado neste trabalho. A última versão apresenta uma sensibilidade de 72,4±0,100 pm/m, entre 0 e 1 m, e uma resolução de 6,9 cm utilizando um interrogador com 5 pm de resolução. Por fim, a estrutura em estudo foi monitorizada por um período de tempo, observando-se as suas frequências naturais. Verifica-se que não existem alterações significativas do valor das frequências naturais, concluindo-se que a estrutura se encontra em bom estado, mantendo as suas propriedades físicas, nomeadamente a sua rigidez. Este trabalho demonstrou a exequibilidade de utilizar sensores óticos interligados com redes de comunicação por fibras óticas em aplicações de monitorização remota.
This dissertation aims the implementation of a remote monitoring system based on optical sensors, namely fibre Bragg grating based sensors. A remote monitoring system, based on an optical accelerometer, was developed and implemented, at the Aveiro University water reservoir, with a sensibility of 87,848 pm/G and 92,351 pm/G for the transversal and longitudinal directions, respectively. The structure to monitor is physically and mathematically described, through numeric models, with the purpose of estimate its natural frequency on the longitudinal and transversal directions. It is implemented and described a remote monitoring system consisting of an optical fibre connection of the structure to the central system, installed at the Instituto de Telecomunicações – Pólo de Aveiro, which can be accessed from any place with an internet connection. A liquid level sensor for future implementation on the same structure was developed. It is also described and characterized, thermal and mechanically, three versions of the liquid level sensor, which has been optimized during this work. The last version has a sensibility of 72,4±0,100 pm/m, between 0 e 1 m, and a resolution of 6,9 cm using an interrogator with a 5 pm resolution. At last, the structure natural frequencies were monitored over a time period. It is verified that there are no significant changes on the value of the natural frequencies, concluding that the structure is at a healthy state, maintaining its physical properties, namely its rigidity. This work demonstrated the successful use of optical sensors interconnected with optical fibre communication networks for remote monitoring applications.
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Sim, Lay M. "Design, manufacturing and testing of smart beams with EFPI strain sensor for damage detection." Thesis, Loughborough University, 2003. https://dspace.lboro.ac.uk/2134/13207.
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This thesis aimed at the development of a fibre optic strain sensor-based damage detection and evaluation system (FODDAS) based on the composite beams. EFPI strain sensors were used with their integrity being assessed. Their performance, either bonded on the surfaces or embedded was examined extensively. They were shown to be adequate and reliable for strain measurements. Through-the-width damages were simulated by artificially-embedded delaminations, which were located at several through-the-thickness locations, each with two different sizes. The overall design considerations were guided by ply stresses and strains which were estimated by using the modified classical lamination theory (CLT). Considerable efforts were devoted to assessing the through-the-thickness mechanical behaviours of the beams containing optical fibres in three-point bending and short beam shear (SBS). They involved various optical fibre orientations with respect to 00 plies / longitudinal axis and at various through-the-thickness locations, each with different number of optical fibres. The understanding of these behaviours paved the way for the evaluation of the beam-based FODDAS. Smart preconditioned beams were subjected to the quasi -static loads whose magnitudes and locations were required to be well controlled. The viability and effectiveness of the beam-based FODDAS was evaluated in terms of strength and strain obtained by the embedded sensor as well as the surface-bonded strain gauges via the cross comparison of ten cases. For the strength, each beam was incrementally loaded up to the ultimate failure either in three-point bending or SBS. After each increment, the beam was unloaded and inspected for damage. For the given locations of EFPI-SS and artificial delamination as well as the sizes of the latter, it was found that the embedded EFPI-SSs were capable of picking up the stiffness degradation when the 10- mm as well as the 20-mm delamination was located at the 29-30 ply interface in the tensile region of a 32-ply quasi-isotropic carbon/epoxy smart composite beam. It was speculated from single tests results that the propagation of the embedded delamination of the sufficient size was able not only to be detected but also to be monitored by the sensors.
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Belhadj, Miled Othman. "Contribution a l'etude du couplage elasto-optique dans une fibre optique en vue d'une application capteur." Paris 6, 1988. http://www.theses.fr/1988PA066054.
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Conception d'un capteur a fibre optique permettant de suivre le comportement mecanique d'une structure sous l'effet d'une sollicitation. Comportement d'une fibre multimode conditionnee par microcourbures et noyee dans une structure a l'aide d'une mesure d'attenuation
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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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Mahieuxe, Bruno. "Capteurs à fibre optique pour le dosage des nitrates." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL046N.
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Les capteurs à fibre(s) optique(s) trouvent de nombreuses applications dans la surveillance de l'environnement et particulièrement pour le contrôle continu et in situ de substances polluantes. Étant donné la toxicité des nitrates et des nitrites, l'objectif de ce travail a été de développer des capteurs chimiques à fibre optique fondés sur la fluorescence de composés sensibles spécifiquement à ces anions, la fluorimétrie étant généralement décrite comme une méthode permettant l'analyse de substances à l'état de traces, de l'ordre du ppm, voire du ppb. L'élaboration d'optodes actives à nécessité plusieurs étapes: le choix d'un indicateur fluorescent sensible aux polluants: la fluorescéine pour les nitrates, le 2,3-diaminonaphtalene ou la 4-aminofluoresceine pour les nitrites, l'étude, en phase homogène, des dosages fluorimétriques des nitrates et des nitrites et notamment de leur sensibilité, le développement de techniques d'immobilisation, par liaison covalente, de l'indicateur à l'extrémité de fibres optiques de différentes natures (en silice ou en polystyrène), la caractérisation des optodes: densité du greffage, stabilité dans le milieu d'analyse, la mise au point de systèmes optiques permettant la mesure qualitative et quantitative de la fluorescence des optodes. Ainsi, des optodes en silice, appliquées au dosage des nitrates, ont pu être élaborées, leur réponse étant linéaire pour des concentrations en nitrates comprises entre 2 10^-6 et 10^-5 mol. L-1 (soit entre 0,12 et 0,62 mg NO3-. L-1 dans le milieu d'analyse). Pour les nitrites, le greffage covalent sur les fibres n'a pu être abordé, néanmoins des solutions ont été proposées
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Vošček, Jakub. "Optické vlákno jako distribuovaný teplotní senzor." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2020. http://www.nusl.cz/ntk/nusl-433164.
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The financial requirements between fiber optic sensors and conventional sensors are gradually declining, which, despite many advatages and wide range of applicationas, has slowed down the demand for these sensors. With the demand for fiber optic sensors also grow the requirements for the parameters of these sensors. This thesis deals with distributed temperature fiber optic sensors. Non--linear phenomen in optical fibers, such as Raman scattering is used for measuring with these sensors. This scatterin was used to obtain information about temperature, which effected the optical cable under the test.
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Lecomte, Pierre. "Mesure haute température en environnement irradié par fibre optique utilisant l’effet Raman." Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0067/document.
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EDF souhaite utiliser la technologie de mesure de température répartie par capteur à fibre optique utilisant l’effet Raman pour réaliser des cartographies de température de certains composants de centrales nucléaires. Les conditions environnementales auxquelles le capteur à fibre optique est soumis sont particulièrement agressives (température de 350 °C et rayonnements gamma ionisants). Les rayonnements ionisants sont responsables de la création de défauts structurels au cœur de la fibre, qui atténuent sa transmission lumineuse, et dont les effets engendrent une erreur de mesure de température pouvant aller jusqu'à l’interruption totale de la mesure. La haute température, quant à elle, dégrade le revêtement protecteur de la fibre optique, ce qui la fragilise mécaniquement. Des irradiations gamma in situ sur des fibres optiques multimodes commerciales à revêtement or protégées par une gaine en acier inoxydable ont été réalisées, à l’aide de deux sources de rayonnements différentes, pour observer l'atténuation radio-induite du capteur à fibre optique en fonction du débit de dose et de la dose cumulée. Les effets du rayonnement à température ambiante, puis à haute température, ont été observés. Ce travail expérimental démontre que la haute température peut être maîtrisée grâce à une fibre à revêtement or, et que la haute température est bénéfique contre l’atténuation de la fibre engendrée par l’irradiation. La mise en œuvre de capteur de température à fibre optique en environnement sévère devient possible, ainsi que l’estimation des incertitudes sur la mesure associéeEDF is working on Raman distributed temperature sensing using optical fiber sensors in order to map temperature of nuclear power plants big components. The sensor has to sustain harsh environmental conditions (temperatures up to 350 °C and gamma ionizing radiations). Ionizing radiations can create structural defects inside the fiber’s core, which attenuate the light transmission. This phenomenon can lead to temperature measurements errors until no measurement is possible. As for high temperature, it can affect the fiber coating, which mitigate the fiber mechanical resistance.Gamma rays in situ irradiations have been carried out over commercial off-the-shelf multimode gold coated fibers protected with a stainless steel metal tubing, with two different radiation sources, in order to observe radiation-induced attenuation over dose rate or cumulated dose. Effects of gamma rays over gold coated optical fiber sensors have been observed at both room anhigh temperature.This experimental work enlightens that high temperature can be controlled with gold coated fibers, and that the radiation-induced attenuation downsides can efficiently be balanced with high temperature. Implementation of a Raman distributed temperature optical fiber sensor in such harsh environments becomes possible, as well as the associated estimation of measurement uncertainty
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Buchoud, Edouard. "Détection, localisation et quantification de déplacements par capteurs à fibre optique." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENU021/document.
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Pour l’auscultation d’ouvrages, les capteurs à fibre optique sont généralement utilisés puisqu’ils présentent l’avantage de fournir des mesures réparties. Plus particulièrement, le capteur basé sur la technologie Brillouin permet d’acquérir un profil de fréquence Brillouin, sensible à la température et la déformation dans une fibre optique sur une dizaine de kilomètres avec un pas de l’ordre de la dizaine de centimètres. La première problématique est d’obtenir un profil centimétrique sur la même longueur d’auscultation. Nous y répondons en s’appuyant sur des méthodes de séparation de sources, de déconvolution et de résolution de problèmes inverses. Ensuite, nous souhaitons estimer la déformation athermique dans l’ouvrage. Pour cela, plusieurs algorithmes de filtrage adaptatif sont comparés. Finalement, un procédé pour quantifier le déplacement de l’ouvrage à partir des mesures de déformation est proposé. Toutes ces méthodes sont testés sur des données simulées et réelles acquises dans des conditions contrôléesFor structural health monitoring, optical fiber sensors are mostly used thanks their capacity to provide distributed measurements. Based on the principle of Brillouin scattering, optical fiber sensors measure Brillouin frequency profile, sensitive to strain and temperature into the optical fiber, with a meter spatial resolution over several kilometers. The first problem is to obtain a centimeter spatial resolution with the same sensing length. To solve it, source separation, deconvolution and resolution of inverse problem methodologies are used. Then, the athermal strain into the structure is searched. Several algorithms based on adaptative filter are tested to correct the thermal effect on strain measurements. Finally, several methods are developed to quantify structure displacements from the athermal strain measurements. They have been tested on simulated and controlled-conditions data
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Yi, Duo. "Intégration de capteurs à fibre optique par projection thermique pour des applications de contrôle de structures intelligentes." Thesis, Belfort-Montbéliard, 2016. http://www.theses.fr/2016BELF0285/document.
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Ce mémoire présente la modélisation, la simulation, l’expérimentation et la conception d’une structure composite intelligente pour des mesures de haute température (jusqu’à 300 °C). Pour ce faire, une fibre à revêtement métallique, particulièrement résistante pour de tels niveaux thermiques, a été considérée et intégrée au sein d’un revêtement d'alumine. La structure composite intelligente se compose alors du substrat, du dépôt et d’un capteur à fibre optique à modulation d’intensité. Pour mener cette étude, une estimation des flux thermiques basée sur le thermogramme expérimental s’est révélée nécessaire afin d’alimenter un modèle numérique. Différents modèles ont ensuite été construits afin d’évaluer les niveaux de températures atteints en surface ainsi que les niveaux de contraintes au sein même du composite. La simulation a montré que le dépôt pouvait thermiquement être considéré comme une couche mince et que la diffusion de la chaleur au sein du dépôt et du substrat était rapide et pouvait être estimée à l'échelle de la milliseconde. La répartition des contraintes est comme on pouvait s'y attendre dépendante du flux incident mais aussi de la géométrie globale du composite. Les contraintes restent relativement uniformes lors de l'échauffement et durant leur propagation mais s’intensifient après le refroidissement. Il s'avère également que les contraintes résultantes ne sont pas symétriques dans la fibre et sont dépendantes de la position de la fibre par rapport au substrat. Après une phase de modélisation des niveaux thermiques et des contraintes susceptibles d’être atteints au sein du matériau, une phase expérimentale consistant à intégrer une fibre optique non fonctionnalisée dans un dépôt d’alumine a donc été réalisée. Les observations microscopiques en surface et en coupe ont été effectuées afin de vérifier l’intégrité de la fibre intégrée. L’adhérence mécanique des fibres a ensuite été mesurée ainsi que l’atténuation optique pendant le processus d’intégration et le comportement thermique de l’ensemble durant des cyclages thermiques. Enfin, un capteur à fibre optique à modulation d’intensité a été conçu par intégration dans un dépôt céramique réalisé par projection thermique. Un système de mesure de la température a donc été construit et les premiers essais de réponse thermique ainsi que le cyclage thermique du capteur de température ont été effectués et analysés. En concluision, cette étude démontre la faisabilité d’une structure composite intelligente par intégration d'un capteur à modulation d’intensité à fibre optique dans un dépôt céramique élaboré par projection thermique susceptible de pouvoir travailler jusqu’à des températures de 300 °CThis paper presents the modeling, simulation, experimentation and design of a smart composite structrure for high temperature measurements (up to 300 °C). In order to achieve this goal, a high temperature resistant metal coated optical fiber was considered and integrated into alumina coating. The smart composite structure consists of a substrate, a coating and an intensity modulated optical fiber temperature sensor. Firstly, an estimation of heat flux based on a experimental thermogram was firstly carried out in order to feed a numerical modeling. Then, different modelings were built to evaluate the surface temperature levels as well as the composite stress levels. The simulation showed that the composite (substrate and coating) could be considered as a thermally thin medium, the heat propagation within the composite was fast and could be estimated at a scale of millisecond. The stresses remained relatively uniform during the heating process but intensified during the cooling process. The modeling also showed that the stresses are not symmetrical in the fiber and depend on the position of the fiber relative to the substrate. After a modeling evaluation of the thermal levels as well as the stresses that may be achieved in the composite, an experimental step integrating a optical fiber into a thermal coating was carried out. Microscopic observation of surface and cross section were conducted in order to analyze the characteristics of the integrated fiber. The mechanical strength of the integrated fiber was then measured and the optical attenuation during the integration process as well as the thermal behavior of the integrated fiber during the thermal cycling were evaluated. Finally, an intensity modulated optical fiber temperature sensor was designed and integrated into ceramic coating by thermal spraying. A temperature measuring system was designed and the first tests of the thermal response as well as thermal cycling of temperature sensor were carried out. This study demonstrates the feasibility of designing a high temperature resistant smart composite structure by integrating an intensity modulated optical fiber temperature sensor in a ceramic coating elaborated by thermal spraying
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Morana, Adriana. "Gamma-rays and neutrons effects on optical fibers and Bragg gratings for temperature sensors." Phd thesis, Université Jean Monnet - Saint-Etienne, 2013. http://tel.archives-ouvertes.fr/tel-01064993.
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The nuclear industry shows an increasing interest in the fiber optic technology for both data communication and sensing applications in nuclear plants. The optical fibers offer several advantages and the sensors based on this technology do not need any electrical power at the sensing point, they have a quick response and they can be easily multiplexed: in the case of a temperature sensor, several thermocouples can be substituted by a single fiber, resulting in a decrease of the waste material. The fission reactors are a very harsh environment: it is characterized by the highest dose of gamma-rays, of the order of magnitude of GGy, besides a high flux of neutrons and high operating temperature (300°C for the current reactors, known as generation III). This work has been carried out in collaboration with AREVA, a French industrial conglomerate active in the energy domain, with the aim of realizing a temperature sensor resistant to the environment of nuclear reactor of generation IV, in particular a Sodium-cooled Fast Reactor. The currently used technology, the thermocouples, presents a drift of the measurement due to irradiation, that needs a calibration, and a long response time on the order of seconds. In order to remove the drift, to reduce the response time and to increase the precision, a Fiber Bragg Grating temperature sensor was chosen, in regard to all the advantages of the optical fibers. To understand the behavior of such system in a harsh environment, as the nuclear reactor core, we used an experimental approach based on complementary techniques such as radiation-induced attenuation, photoluminescence, electron paramagnetic resonance and Raman spectroscopies
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Henault, Jean-Marie. "Approche méthodologique pour l’évaluation des performances et de la durabilité des systèmes de mesure répartie de déformation : application à un câble à fibre optique noyé dans le béton." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1113/document.
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La surveillance des structures de génie civil, afin d'en estimer l'état de santé, est un enjeu majeur pour les maîtres d'ouvrages. Les systèmes de mesures réparties par fibre optique, composés d'un interrogateur connecté à une fibre optique intégrée dans un câble, permettent de mesurer le profil de déformation avec un pas de mesure centimétrique et une portée kilométrique. Ils sont donc adaptés aux structures présentant de grands linéaires ou de grandes surfaces. Mais, avant tout déploiement industriel, il est nécessaire d'en évaluer leurs performances. Du fait de la déformation par cisaillement du revêtement du câble, le profil de déformation mesuré le long de la fibre optique n'est pas strictement identique à celui du matériau environnant. Une méthode, basée sur la mise en œuvre d'essais et de simulations numériques, a été développée afin de caractériser les mécanismes de transfert d'effort du milieu hôte à la fibre optique à travers le revêtement du câble. Cette méthode a été appliquée pour déterminer la réponse mécanique d'un câble particulier noyé dans le béton. Les performances métrologiques d'un système de mesure donné ont été évaluées sur la base d'une analyse d'essais « du laboratoire au terrain ». Cette étude a permis de quantifier les différentes composantes d'incertitude et d'estimer les performances du système de mesure complet. Enfin, le câble, noyé dans le béton, ne peut être remplacé. La connaissance de l'impact du vieillissement sur la réponse mécanique du câble est donc primordiale. Une étude spécifique est menée dont le but est d'estimer la durabilité du câble face aux sollicitations chimique, thermique et mécanique correspondant à une application donnéeStructural Health Monitoring is a key factor in life-cycle management of civil structures. Truly distributed fiber optic sensors, composed by an optoelectronic device paired with an optical fiber in a cable, provide strain profiles over several kilometers with a centimeter resolution. They are thus able to provide relevant information on large structures. However, a preliminary performance assessment is required prior to any industrial application. Due to shear deformation of the cable's protective coating, strain measurements provided by the measuring system may differ from actual strains in the embedding medium. A methodology, based on mechanical tests and modelling, was thus developed to determine the relationship between measured/actual strains. It was applied to determine the mechanical response of a specific cable embedded in concrete. Performance assessment method was applied to a specific measuring system. Tests were carried out under laboratory conditions on the fiber optic cable, out of the concrete medium in a first stage, and then embedded in concrete structures. It enabled to evaluate its components and standard uncertainties. The cable could not be replaced after being embedded in concrete. It is necessary to evaluate the ageing effects on its mechanical properties to use it for a long term period. A specific study was carried out to determine the cable durability under chemical, thermal and mechanical solicitations
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Ronot-Trioli, Catherine. "Etude de polymères spécifiques pour la détection du méthane et de vapeurs chimiques à l'aide d'un capteur intrinsèque à fibre optique." Saint-Etienne, 1993. http://www.theses.fr/1993STET4018.
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Le sujet de ce mémoire est l'étude de gaines de polymères spécifiques pour la détection du méthane et de vapeurs chimiques à l'aide d'un capteur intrinsèque à fibre optique. La mesure de ce dispositif est basée sur la variation de l'indice de gaine optique après absorption du gaz dans le polymère. Le maximum de sensibilité est obtenu pour un angle d'incidence du faisceau lumineux sur la face d'entrée de la fibre légèrement supérieur à l'angle correspondant à l'ouverture numérique de la fibre, pour lequel seuls certains rayons non méridiens sont guidés. D'un point de vue chimique, la sensibilité peut être améliorée si l'on incorpore dans le polymère des fonctions chimiques capables d'interagir avec le gaz à détecter. Afin de détecter des hydrocarbures, nous avons sélectionné des gaines de polymère hydrophobe. Le dépôt de ces polymères hydrophobes sur la silice hydrophile a conduit à des inhomogénéités de surface que nous avons pu atténuer en modifiant l'interface sur gaine selon une technique de silanisation. Des tests ont été réalisés pour différentes gaines de polymères hétéropolysiloxanes sur les vapeurs chimiques suivantes : méthane, heptane, toluène, éthanol, dichlorométhane, tétrachlorure de carbone et eau. Si les gaines de polymère spécifique permettent de détecter sélectivement les hydrocarbures vis-à-vis d'interférants chimiques, le capteur ne présente, en revanche, aucune sélectivité pour des composés appartenant à une même famille de composés