Dissertations / Theses: 'Fibre optic sensor networks'

1

Street, Andrew M. "Spread spectrum techniques for multiplexing and ranging applications." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259828.

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2

Zhang, Kuiwei. "Surface roughness and displacement measurements using a fibre optic sensor and neural networks." Thesis, Brunel University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246145.

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3

Fang, Xiaojun. "Nonreciprocal effects and their applications in fiber optic networks." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/40337.

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Nonreciprocity is a fundamental property of networks. Unlike electronic networks theory, optical network theory is still a field to be investigated. Lightwave systems, including fiber optic and integrated optic, are becoming more and more complex, new function blocks ( or components) and networking strategies are very important for future highly integrated lightwave circuits. Several common nonreciprocal optical effects studied in this disseration and several basic applications to fiber components and fiber optic metrology systems analyzed. The common optical nonreciprocal phenomena include the Faraday effect, Sagnac effect, Fresnel drag effect, nonlinearity or asymmetric geometric structure-induced nonreciprocity, and some pseudo nonreciprocity. The best-known application of nonreciprocity to optical components is the isolator, and the known nonreciprocity-based fiber optic sensors are the fiber optic gyroscope and the fiber optic current sensor. The major difficulty in forming a general optical network theory is the complexity of optical signals compared to the electrical signal, because each light signal consists of four independent parameters, all of which changing during transmission. Fortunately, most optical signals can be classified into intensity-based and phase-based systems, and the Jones matrix technique is the ideal tool for describing the intensity-based system. Several reciprocity-insensitive structures designed and analyzed in chapter 3. The performance of the intensity-based reciprocity-insensitive structure (IRIS) was employed successfully in a fiber optic current sensor for stabilizing the signal from birefringence influences in chapter 5. A variable-loop Sagnac interferometer was designed and applied to distributed sensing in chapter 6, and the reciprocity-insensitive property of the Sagnac interferometer was preserved. Polarization independent isolators and wavelength division multiplexers were also realized by employing suitable nonreciprocal effects and were discussed in chapter 2 and chapter 4, and their feasibilities were verified by experiment. The primary contributions of this dissertation are the study of common nonreciprocal optical effects and demonstration of several basic applications to fiber components and fiber metrology systems.
Ph. D.

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Goyal, Sandeep. "Fiber optic current sensor network." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq24716.pdf.

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Canalizo, M. Andres E. "Fiber optic current sensor network, innovations and applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0019/MQ48057.pdf.

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6

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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7

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.

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8

Levin, Klas. "Durability of Embedded Fibre Optic Sensors in Composites." Doctoral thesis, Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3145.

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9

Farahi, F. "Fibre optic interferometric thermometers and multiplexed systems." Thesis, University of Kent, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382854.

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10

McCulloch, Scott. "Fibre optic microsensors for intracellular chemical measurements." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248617.

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11

Ingold, Joseph Patrick. "Fiber optic sensors and networks for U.S. Navy shipboard tests and trials." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/41974.

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After a U. S. Navy ship is built but before it is placed into service, many performance tests of all shipboard systems are conducted. These tests vary greatly in who performs the test, the purpose of each test, which system or systems are being tested, and the duration of each test. As naval warfare ships become increasingly complicated, the performance tests that are conducted also become numerous and complex. The current test philosophy prescribes that for each test and test organization, telemetry cables for electrical sensors are strung throughout the ship immediately prior to the test being conducted. As the shipboard tests and trials become more numerous and complex this philosophy becomes expensive from a labor and materials point of view.

This thesis proposes an economical solution to the current test and trials problem by offering a fiber optic network with optical sensors. The fiber optic network will be designed to accommodate as many different users as possible, and it will be installed once, during the new ship construction. Prior to the network design, optical fiber sensor schemes are discussed. One sensing scheme, using quartz crystal oscillators, looks promising for the test and trials application. This one sensing method can be applied to acceleration, velocity, displacement, temperature, current, and voltage. Thus economies can be realized by using one network and sensor type for the majority of tests and trials applications.
Master of Science

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12

Bownass, David Casson. "Passive fibre-optic humidity sensing for telecommunications networks." Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/1191.

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MacPherson, William Neil. "Fibre optic sensors for applications in turbomachinery research." Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/585.

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14

McMurtry, Stefan. "Multipoint humidity sensing based upon a multiplexed fibre optic sensor." Thesis, University of Kent, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310209.

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15

Nieves, Bogonez Francisco Daniel. "Manufacturing and characterisation of a fibre optic acoustic emission sensor." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7762/.

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The value of Remote Condition Monitoring for the real-time evaluation of the structural integrity of critical components is undeniable. Fibre-reinforced polymer composites are a class of materials which offer significant advantages over conventional metal alloys used for manufacturing load bearing structures in cases where weight and/or energy consumption need to be kept to a minimum, for example automotive and aerospace applications. This is due to the excellent strength to weight ratio that FRPCs exhibit. However, their strongly anisotropic microstructure of poses significant challenges for Non-Destructive Evaluation of the actual structural health of components made from such materials. Acoustic Emission is a passive condition monitoring technique based on the detection of elastic stress waves emitted when damage evolves in a structure. Conventional piezoelectric AE sensors need to be surface-mounted as their embedding in FRPCs is impractical. Fibre Optic Acoustic Emission Sensors (FOAES) offer a distinct advantage since they are light weight, have small size and can be effectively embedded in composite laminates. Moreover, they can be multiplexed with the entire structure being monitored more effectively. This study has focused in the evaluation of the manufacturing process and characterisation of FOAES. Comparison of their performance with conventional commercial sensors was carried out.

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Burns, Jonathan Mark. "Development and characterisation of a fibre-optic acoustic emission sensor." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3409/.

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A requirement for online monitoring has emerged owing to the susceptibility of fibre reinforced composite materials to sub-surface damage. Acoustic emission (AE) monitoring is understood to detect damage well before catastrophic failure; research in AE sensing therefore continues to attract significant attention. The research presented herein provides a review of a fibre-optic-based AE sensor design. Developmental work was performed to evaluate both sensor fabrication and packaging-related issues. The characteristics of the sensor were found to be influenced by: (i) the type of optical fibre used for fabrication; and (ii) preparation of optical fibres prior to sensor fabrication. The use of a small-diameter packaging substrate revealed improvements in sensor performance. The fibre-optic AE sensor was successfully embedded in a uni-directional composite laminate that was fabricated using autoclave processing. The embedded fibre-optic sensor was found to provide higher sensitivity to simulated AE compared with a surface-mounted sensor. Sensor characterisation trials were performed using simulated AE; a low directional sensitivity was observed. Modal analysis revealed a preferential sensitivity to the A0 wavemode; this sensor design may therefore be suited to the detection of delamination in FRCs. Finally, the sensor was shown to successfully detect interlaminar crack propagation under Mode-I loading.

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17

King, David Gareth. "Fibre-optic sensor development for process monitoring of epoxy resins." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8698/.

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An investigation was undertaken to examine the performance of a Fresnel reflection sensor (FRS) incorporated into a differential scanning calorimeter (DSC) to track the cross-linking of epoxy resins. The initial design used a micrometer translation stage to lower the FRS through an orifice in the DSC platinum lid and onto the pan containing the sample. During exothermic cross-linking experiments, the resin refractive index and the heat evolved were measured simultaneously, allowing for direct comparison between the data. Combining the two measurement techniques produced a powerful hyphenated analytical procedure that demonstrated the feasibility of using the FRS for in-situ cure monitoring of epoxy resin systems. During the cross-linking of specified resins, the sensor revealed optical phenomena throughout the latter stages and was shown to be sensitive to the glass transition temperature, nano-particulate movement, nano-particulate concentration and phase separation. Therefore, the introduction of the FRS to the DSC provided valuable cross-linking information. A second modification to the DSC permitted the accommodation of an optical fibre probe, which facilitated simultaneous DSC/FRS/Fourier transform infrared spectroscopy (FTIRS) analysis. Good correlation between the cross-linking kinetics of an epoxy resin system was demonstrated using the hyphenated techniques and hence alleviated the issues of cross-correlation between individual experiments.

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18

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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19

Sun, Tong. "Fluorescence-based fibre optic sensor systems for temperature and strain measurement." Thesis, City University London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287664.

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Fneer, Mohamed K. "Development of fibre optic based ammonia sensor for water quality management." Thesis, City University London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.363350.

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21

Sloan, William D. "The development of a fibre-optic chemical sensor for calcium ions." Thesis, Glasgow Caledonian University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251184.

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Clowes, John Redvers. "Fibre optic pressure sensor for downhole monitoring in the oil industry." Thesis, University of Southampton, 2000. https://eprints.soton.ac.uk/42437/.

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Cost-effective oil and gas production is becoming more important than ever. The availability of downhole information is seen to be the key to increasing oil-recovery efficiency, currently estimated to be 35% on average for North Sea oil-wells. The SD-series pressure sensor out-performs any existing downhole pressure gauge in the world and is to be made commercially-available to the global oil industry in the year 2000.

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23

Khalil, Nahla Mahmood. "Novel optoelectronic temperature sensor having application in the biomedical field." Thesis, City University London, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328417.

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Madruga, Saavedra Francisco Javier. "Contribución al desarrollo de sensores de temperatura y redes de sensores en tecnología de fibra óptica." Doctoral thesis, Universidad de Cantabria, 2006. http://hdl.handle.net/10803/10707.

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Este trabajo de tesis recoge las contribuciones aportadas en el campo de los sensores de fibra óptica en tres ámbitos de trabajo. Un sistema sensor de alta temperatura sin contacto con transductores de fibras ópticas de sílice se ha presentado. Dos topologías de "ojo abierto" y "ojo cerrado" y un algoritmo de decodificación "pirometría de banda dual" propuesto en este trabajo son las novedosas aportaciones presentadas. El sistema ha sido validado en laboratorio y en pruebas de campo de forma exitosa. Para sensores de temperatura con fibras dopadas con Erbio se ha demostrado que su máxima sensibilidad tiene lugar cuando la longitud utilizada es superior a la óptima exigida por el bombeo. Finalmente se ha modelado y validado en laboratorio una red de sensores acústicos basados en interferómetros Fabry-Perot de cavidad larga determinando a partir del modelo obtenido la fase mínima detectable y la visibilidad máxima del sistema.
The thesis collects contributions in the field of optic fibre sensors for three areas. A high temperature sensor system without contact based on silica optic fibre transducers has been submitted. Two topologies "open eye" and "closed eye" and a dual band pyrometer decoding algorithm are the submitted innovative contributions. The system has been validated successful in the laboratory and field tests so. Another contribution has been the demonstration that the maximum sensitivity for temperature sensors based on Er-doped fibres occurs when the used length is more than the optimum required by pumping. Finally a network of acoustic sensors based on Fabry-Perot fibre interferometers has been modelled and validated in the laboratory. The minimum detectable phase and maximum visibility of the system has been obtained from the proposed and validated model

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Cooper, David J. F. "Time division multiplexing of a serial fibre optic Bragg grating sensor array." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/MQ45424.pdf.

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26

Orr, Philip J. G. "Magnetophotonic sensor systems for fibre-optic magnetic diagnostics in tokamak fusion reactors." Thesis, University of Strathclyde, 2011. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23931.

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Electrical power generation through controlled nuclear fusion has the potential to make a substantial contribution to the global generation pool within the next century. However, continuous operation of fusion reactors is not yet achieved. As such, a key objective of the next-generation machines is to increase the duration of operational pulses. As fusion reactors progress towards steady-state operation, the use of present inductive transducers as part of critical magnetic diagnostic systems becomes increasingly unfeasible. In this thesis, it is proposed that due to their record of high performance in adverse conditions, optical fibre sensors may be the most appropriate alternative measurement technology. However, in order to reap the benefits associated with fibre sensors - such as minimised wiring, serial multiplexing, and electrical and chemical passivity - a new class of intrinsic point sensors is required that can operate within the extremely harsh nuclear fusion environment . To achieve this, two spectrally-encoding reflection-mode sensors that function on a purely magnetophotonic basis are developed, since it is shown that only this mechanism will succeed in the fusion environment. By exploiting the nonreciprocality of the Faraday effect, it is shown how fibre Bragg gratings incorporating structural defects can yield enhanced, localised measurements. An alternative scheme enables direct measurement of the magnetic circular birefringence using polarisation mode switching. Both techniques provide a true all-fibre point measurement of magnetic field and retain serial multiplexing capabilities. Additionally, a supporting interrogation system is demonstrated that combines high-resolution measurement with high-speed multiplexing. The transducers and associated systems described in this thesis are shown to meet the criteria both for performance and for environmental robustness. As such, their further development as part of a tokamak magnetic diagnostic scheme is recommended.

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Haaksman, Ronald P. H. "Design of a fibre optic acoustic sensor array : sensitivity and noise properties." Thesis, University of Southampton, 2002. https://eprints.soton.ac.uk/15486/.

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In this thesis the study of a multiplexed Fibre Optic Acoustic Sensor (FOAS) system is presented. Narrowband reflectors (Fibre Bragg Gratings or FBGs) define sensing sections of 12.5 metres, which then act as Fabry-Perot (FP) cavities. Low-coherence interferometry is used to interrogate the sensors with an accuracy of 50 µrad/√Hz, in good agreement with the theoretically predicted value. Heterodyne signal processing is used to eliminate low frequency environmental noise. The performance of the sensor is checked by a sinusoidal calibration signal generated by a PZT fibre stretcher. The sensor has a flat frequency response at 10 kHz with a high sensitivity of 50 µrad/√Hz and a dynamic range of 80 dB. The use of FBG based interferometers allows the use of Wavelength Division Multiplexing (WDM) technology allowing us to multiplex large number of sensors in the system. The sensing system uses Amplified Spontaneous Emission (ASE) sources for illumination purposes. ASE sources are an attractive option for interrogating arrays of FBG sensors. The coherence features of broadband ASE light makes it attractive to be used in sensing applications, since Coherence Multiplexed (CM) systems interrogated with these sources do not suffer from phase induced intensity noise, which is a problem when employing laser sources. It is well known that ASE sources suffer from excess photon noise, which is the dominant type of noise and hence limits the systems sensitivity. To get an idea of the impact of this type of noise on the performance of the system, the noise properties have been studied in detail both theoretically and experimentally. Noise spectra are calculated from the autocorrelation function of the output detector current for a thermal-like source. It is well known that unbalanced interferometers (with delay time T) act as filtering elements and produce a noise spectrum with peaks at integer multiples of 1/T, due to filtered source intensity noise. The noise analysis is used to evaluate the performance of the sensor system, and to calculate the optimum reflectivity of both FBGs in the FP sensing cavity. Optimum reflectivities for both FBGs in the FP sensors have been found. Theoretical calculations show that the best phase resolution and visibility is obtained for R1 = 40 % and R2 = 100 %. This has been verified with experiments. We also established the robustness of the system to FBG drift. A first demonstration of a FOS interrogation system using a low-coherence ASE source with a Semiconductor Optical Amplifier (SOA) is presented. The SOA is Gain-Saturated and thereby reduces the dominant intensity noise originating from the ASE source, improving the systems Signal to Noise Ratio (SNR).

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28

Pung, H. K. "Flood routing techniques for fibre optic local area networks with arbitrartopology." Thesis, University of Kent, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332715.

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29

Barton, Elena. "Detection of matrix cracking in a GFRP laminate using a fibre optic sensor." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/2230/.

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30

Hickey, Michelle. "A new fibre optic photoplethysmographic sensor for the assessment of splanchnic organ perfusion." Thesis, City University London, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508374.

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A new reflectance fibre optic photoplethysmographic (PPG) sensor, comprising of red (660 nm) and infrared (850 nm) emitters, a photodiode and 600 ?m fibre optic cables, was developed to allow for the intraoperative assessment of PPG signals and the preliminary estimation of SpO2 from splanchnic organs. An identical peripheral sensor was also developed to allow for the qualitative and quantitative comparison between PPG signals obtained from splanchnic organs and those from the traditional peripheral site (finger or toe). A three channel instrumentation system (splanchnic PPG, peripheral PPG, and ECG) and software algorithms implemented in LabVIEW allowed for the continuous acquisition of PPG and ECG signals and the estimation of SpO2. The feasibility of the fibre optic sensors to allow for sufficient illumination of the tissue and to adequately detect PPG signals was explored and validated in the laboratory. A detailed investigation to determine the optimal transmitting-receiving fibre separation distance, found that the optimum separation distance was between 3 mm and 4 mm. An in vivo evaluation of the fibre optic splanchnic PPG sensor on 20 patients under-going open laparotomy demonstrated that good quality PPG signals can be obtained from the surface of the small bowel, large bowel, liver and stomach. Due to underlying differences in vasculature, the splanchnic ac and dc PPG signals were found to be of larger amplitudes than those obtained from the periphery, and statistical analysis showed that there is a statistical significant difference between splanchnic and peripheral PPG signals. Also, preliminary estimation of SpO2 from the uncalibrated fibre optic splanchnic sensor showed good agreement between the SpO2 estimated at the periphery. The results from the clinical measurements have confirmed that fibre optic pulse oximetry might be the way forward in monitoring splanchnic perfusion.

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Harvey, Daniel Peter. "The combination of smart hydrogels and fibre optic sensor technology for analyte detection." Thesis, Aston University, 2011. http://publications.aston.ac.uk/15806/.

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The subject of investigation of the present research is the use of smart hydrogels with fibre optic sensor technology. The aim was to develop a costeffective sensor platform for the detection of water in hydrocarbon media, and of dissolved inorganic analytes, namely potassium, calcium and aluminium. The fibre optic sensors in this work depend upon the use of hydrogels to either entrap chemotropic agents or to respond to external environmental changes, by changing their inherent properties, such as refractive index (RI). A review of current fibre optic technology for sensing outlined that the main principles utilised are either the measurement of signal loss or a change in wavelength of the light transmitted through the system. The signal loss principle relies on changing the conditions required for total internal reflection to occur. Hydrogels are cross-linked polymer networks that swell but do not dissolve in aqueous environments. Smart hydrogels are synthetic materials that exhibit additional properties to those inherent in their structure. In order to control the non-inherent properties, the hydrogels were fabricated with the addition of chemotropic agents. For the detection of water, hydrogels of low refractive index were synthesized using fluorinated monomers. Sulfonated monomers were used for their extreme hydrophilicity as a means of water sensing through an RI change. To enhance the sensing capability of the hydrogel, chemotropic agents, such as pH indicators and cobalt salts, were used. The system comprises of the smart hydrogel coated onto an exposed section of the fibre optic core, connected to the interrogation system measuring the difference in the signal. Information obtained was analysed using a purpose designed software. The developed sensor platform showed that an increase in the target species caused an increase in the signal lost from the sensor system, allowing for a detection of the target species. The system has potential applications in areas such as clinical point of care, water detection in fuels and the detection of dissolved ions in the water industry.

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Heininger, Hilmar. "Využití optovláknových senzorů pro aplikace ve stavebním inženýrství při použití široce přeladitelného laseru." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-233659.

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Předložená disertační práce zkoumá možnosti použití nového typu polovodičového MGY- Laseru elektricky laditelného v širokém spektrálním rozsahu a zabývá se možnostmi jeho nasazení v optovláknové senzorové síti založené na metodě FBG (Fiber Bragg Grating). Výzkum byl započat komplexními dlouhodobými testy reálného měřícího scénáře z oblasti stavebnictví, sestaveného pro účely ověření limitujících aspektů současných technik. Inženýrské aplikace nabízejí velké množství vzájemně se vylučujících požadavků pro návrh strukturálních senzorových systémů. Tyto požadavky jsou sdíleny mnoha dalšími technologickými oblastmi, což přispívá k vysokému stupni univerzálnosti použití dosažených výsledků. Na základě posouzení stavu současné techniky a aplikačních požadavků byly v práci nejprve identifikovány aspekty, které mají být výzkumem zlepšeny. V dalším kroku byl detailně charakterizován MG-Y laser Syntune/Finisar S7500. Na základě dat získaných měřením byla zkoumána nová metoda spojitého řízená vlnové délky záření laseru. Provedené experimenty vedly nejen k návrhu nového způsobu spojité regulace vlnové délky ale také k vytvoření prostředků pro vlastní kalibraci systému na základě jeho vnitřních vlastností (podélných módů rezonátoru).

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Hadley, Glyn James Matthew. "Development and in-vitro evaluation of a potentially implantable fibre-optic glucose sensor probe." Thesis, Bournemouth University, 2002. http://eprints.bournemouth.ac.uk/404/.

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Type I diabetics need regular injections of insulin to survive. Insulin allows the cells of the body to extract glucose from the blood supply to use as fuel. Without insulin the cells turn to other backup fuel sources,this can cause side effects that are quickly fatal or gradual wasting of the bodies tissues. The use of insulin, however, is not danger free, as an incorrect dosage can quickly lead to the reduction of glucose circulating in the blood to drop to a dangerously low level. Without glucose circulating in the blood supply the brain quickly runs out of fuel causing coma and death. Because of this, a means to constantly monitor blood glucose levels has been sought for the last two decades. With such a device, diabetics could judge the correct amount of insulin to inject and be warned of low blood glucose levels. However, to date no reliable portable system has been produced. Recent developments in fibre optic biosensor technology, suggested a possible route to achieves this goal. The work in this thesis presents the development and testing of such a sensor. The sensor presented in this thesis is based around a commercial fibre optic blood gas sensor, the Paratrend 7. The oxygen-sensing element of this device was modified into a glucose sensor using polymer membranes incorporating the enzymes glucose oxidase and catalase. The research was aimed at building a glucose sensor that could be developed into a working blood glucose sensor in the minimum amount of time if the research proved successful. For this reason the Paratrend 7 sensor system was chosen to provide a clinically tested sensor core around which the glucose sensor could be built. The initial experiment, which used a Paratrend7 sensor coated in polyHEMA and glucose oxidase, produced a sensor of diameter of 700µm with a range of 0 to 4mM/1 of glucose and a 90% response time of <100 seconds in a solution with a 15% oxygen tension. The sensor design was then developed to incorporate the enzyme catalase to protect the glucose oxidase and an outer diffusion limiting polyHEMA membrane. This produced a sensor with a range of 0 to 6 mM/l and a response time of <100 seconds. The method of coating the sensors was'then improved, through a series of stages, until an optomised dip coating technique was developed. This technique produced sensors with ranges (in 7.5KPa oxygen tension solutions) between 0 to 3mM/l and 0 to lOmM/1, responsetimes of <100 seconds in some cases and with diameters of 300µm. By using a partial polyurethane outer coat the range of the sensors was increased form 0 to 4mM/l up to 0 to 24mM/1, in one case, with 90% response times in the 100to 500 second range. The sensors were then sterilised using gamma radiation and their performance before and after sterilisation examined. The gamma sterilisation was found to cause a reduction in the range of the sensors,for example 0 to 24 m /I down to 0 to 14mM/l in one case. The affect of 24 hour operation in a 5mM/1 solution of glucose and storage, for up to three months, was then investigated. Both processes were found to reduce the operational range of the sensors,0 to 20 reduced to 0 to 15 mM/i, in one case,for 24 hour operation and form 0 to 15mM/1 reduced to 0 to 11mM/1in one case for a storage time of three months. The use of the enzymes glucose oxidase and catalase together in a fibre optic as can sensor has not been previously reported in the literature as far be ascertained. The comparison of sensor performance before and after gamma sterilisation also appears to be unique as does the gamma sterilisation of a fibre optic glucose sensor.

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Weaver, R. C. "A fibre-optic microcalorimeter for studying interactions of gases with thin film sensor materials." Thesis, University of Kent, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233913.

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35

Jason, Johan. "Theory and Applications of Coupling Based Intensity Modulated Fibre-Optic Sensors." Licentiate thesis, Mid Sweden University, Department of Information Technology and Media, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-7057.

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Optical fibre sensors can be used to measure a wide variety of properties. In some cases they have replaced conventional electronic sensors due to their possibility of performing measurements in environments suffering from electromagnetic disturbance, or in harsh environments where electronics cannot survive. In other cases they have had less success mainly due to the higher cost 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 photo diodes. The sensor principle itself is very simple when based on coupling between fibres, and coupling based intensity modulated sensors have found applications over a long time, mainly within position and vibration sensing. In this thesis new concepts and applications for intensity modulated fibre-optic sensors based on coupling between fibres are presented. From a low-cost and standard component perspective alternative designs are proposed and analyzed in order to find improved performance. The development of a sensor for an industrial temperature sensing application, involving aspects on multiplexing and fibre network installation, is presented. Optical time domain reflectometry (OTDR) is suggested as an efficient technique for multiplexing several coupling based sensors, and sensor network installation with blown fibre in micro ducts is proposed as a flexible and cost-efficient alternative to traditional cabling. A new sensor configuration using a fibre to a multicore fibre coupling and an image sensor readout system is proposed. With this system a high-performance sensor setup with a large measurement range can be realised without the need for precise fibre alignment often needed in coupling based sensors involving fibres with small cores. The system performance is analyzed theoretically with complete system simulations on different setups. An experimental setup is made based on standard fibre and image acquisition components, and differences from the theoretical performance are analyzed. It is shown that sub-µm accuracy should be possible to obtain, being the theoretical limit, and it is further suggested that the experimental performance is mainly related to two error sources: core position instability and differences between the real and the expected optical power distribution. Methods to minimize the experimental error are proposed and evaluated.

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Kunert, Kristina. "Fibre-Optic AWG Networks Supporting Real-Time Communication in High-Performance Embedded Systems." Licentiate thesis, Halmstad University, Embedded Systems (CERES), 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-56.

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High-performance embedded systems communicating heterogeneous traffic with high bandwidth and strict timing requirements are in need of more efficient communication solutions. This thesis proposes two multi-wavelength passive optical networks able to meet these demands. The networks are based upon a single-hop star topology with an Arrayed Waveguide Grating (AWG) placed in the centre. The intended application areas for the two networks are short range embedded communication systems like System Area Networks (SANs) and router architectures with electronic queuing. The AWG’s attractive property of spatial wavelength reuse, as well as the combination of fixed-tuned and tuneable transceivers in the end nodes, enables simultaneous control and data traffic transmission. This, in turn, makes it possible to support heterogeneous traffic with both hard and soft real-time constraints.

Additionally, two Medium Access Control (MAC) protocols, one for each network solution, are developed. Traffic scheduling is centrally controlled by a node, the protocol processor, residing together with the AWG in a hub. All nodes use Earliest Deadline First (EDF) scheduling and communicate with the protocol processor through physical control channels. A case study, including simulations, in the field of Radar Signal Processing (RSP) and simulations using periodic real-time traffic are conducted for the two application areas respectively, showing very good results. Further, a deterministic real-time analysis is conducted to provide throughput and delay guarantees for hard real-time traffic and an increase in guaranteed traffic is achieved through an analysis of existing traffic dependencies in a multichannel network. Simulation results incorporating the traffic dependency analysis indicate a considerable increase in the possible guaranteed throughput of hard real-time traffic.

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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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Clark, Joanne Louise. "Laser cooling in the condensed phase." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266518.

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Mei, Ying. "Error analysis for distributed fibre optic sensing technology based on Brillouin scattering." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/278660.

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This dissertation describes the work conducted on error analysis for Brillouin Optical Time Domain Reflectometry (BOTDR), a distributed strain sensing technology used for monitoring the structural performance of infrastructures. Although BOTDR has been recently applied to many infrastructure monitoring applications, its measurement error has not yet been thoroughly investigated. The challenge to accurately monitor structures using BOTDR sensors lies in the fact that the measurement error is dependent on the noise and the spatial resolution of the sensor as well as the non-uniformity of the monitored infrastructure strain conditions. To improve the reliability of this technology, measurement errors (including precision error and systematic error) need to be carefully investigated through fundamental analysis, lab testing, numerical modelling, and real site monitoring verification. The relationship between measurement error and sensor characteristics is firstly studied experimentally and theoretically. In the lab, different types of sensing cables are compared with regard to their measurement errors. Influences of factors including fibre diameters, polarization and cable jacket on measurement error are characterized. Based on experimental characterization results, an optics model is constructed to simulate the Brillouin back scattering process. The basic principle behind this model is the convolution between the injected pulse and the intrinsic Brillouin spectrum. Using this model, parametric studies are conducted to theoretically investigate the impacts of noise, frequency step and spectrum bandwidth on final strain measurement error. The measurement precision and systematic error are then investigated numerically and experimentally. Measurement results of field sites with installed optical fibres displayed that a more complicated strain profile leads to a larger measurement error. Through extensive experimental and numerical verifications using a Brillouin Optical Time Domain Reflectometry (BOTDR), the dependence of precision error and systematic error on input strain were then characterized in the laboratory and the results indicated that a) the measurement precision error can be predicted using analyzer frequency resolution and the location determination error and b) the characteristics of the measurement systematic error can be described using the error to strain gradient curve. This is significant because for current data interpretation process, data quality is supposed to be constant along the fibre although the monitored strain for most of the site cases is non-uniformly distributed, which is verified in this thesis leading to a varying data quality. A novel data quality quantification method is therefore proposed as a function of the measured strain shape. Although BOTDR has been extensively applied in infrastructure monitoring in the past decade, their data interpretation has been proven to be nontrivial, due to the nature of field monitoring. Based on the measurement precision and systematic error characterization results, a novel data interpretation methodology is constructed using the regularization decomposing method, taking advantages of the measured data quality. Experimental results indicate that this algorithm can be applied to various strain shapes and levels, and the accuracy of the reconstructed strain can be greatly improved. The developed algorithm is finally applied to real site applications where BOTDR sensing cables were implemented in two load bearing piles to monitor the construction loading and ground heaving processes.

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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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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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42

Shaar, A. A. "A study of code-division multiple-access with reference to fibre-optic local-area networks." Thesis, University of Kent, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353184.

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Howie, Judith Ann Barnard. "An investigation into the use of fluorescent compounds as detecting materials in a fibre optic anaesthetic gas sensor." Thesis, University of the West of England, Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387333.

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Ellis, Andrew. "All optical networking beyond 10 Gbits/s OTDM networks based on electro-optic modulators and fibre ring lasers." Thesis, Aston University, 1997. http://publications.aston.ac.uk/7978/.

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This thesis examines options for high capacity all optical networks. Specifically optical time division multiplexed (OTDM) networks based on electro-optic modulators are investigated experimentally, whilst comparisons with alternative approaches are carried out. It is intended that the thesis will form the basis of comparison between optical time division multiplexed networks and the more mature approach of wavelength division multiplexed networks. Following an introduction to optical networking concepts, the required component technologies are discussed. In particular various optical pulse sources are described with the demanding restrictions of optical multiplexing in mind. This is followed by a discussion of the construction of multiplexers and demultiplexers, including favoured techniques for high speed clock recovery. Theoretical treatments of the performance of Mach Zehnder and electroabsorption modulators support the design criteria that are established for the construction of simple optical time division multiplexed systems. Having established appropriate end terminals for an optical network, the thesis examines transmission issues associated with high speed RZ data signals. Propagation of RZ signals over both installed (standard fibre) and newly commissioned fibre routes are considered in turn. In the case of standard fibre systems, the use of dispersion compensation is summarised, and the application of mid span spectral inversion experimentally investigated. For green field sites, soliton like propagation of high speed data signals is demonstrated. In this case the particular restrictions of high speed soliton systems are discussed and experimentally investigated, namely the increasing impact of timing jitter and the downward pressure on repeater spacings due to the constraint of the average soliton model. These issues are each addressed through investigations of active soliton control for OTDM systems and through investigations of novel fibre types respectively. Finally the particularly remarkable networking potential of optical time division multiplexed systems is established, and infinite node cascadability using soliton control is demonstrated. A final comparison of the various technologies for optical multiplexing is presented in the conclusions, where the relative merits of the technologies for optical networking emerges as the key differentiator between technologies.

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Dokos, Leonidas. "In-situ detection and assessment of low velocity impact-induced damage in composite materials using developed fibre optic sensor technology." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420204.

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46

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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Stevens, Renaud. "Modulation Properties of Vertical Cavity Light Emitters." Doctoral thesis, Stockholm : Tekniska högsk, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3240.

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Enckell, Merit. "Lessons Learned in Structural Health Monitoring of Bridges Using Advanced Sensor Technology." Doctoral thesis, KTH, Bro- och stålbyggnad, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-48131.

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Structural Health Monitoring (SHM) with emerging technologies like e.g. fibre optic sensors, lasers, radars, acoustic emission and Micro Electro Mechanical Systems (MEMS) made an entrance into the civil engineering field in last decades. Expansion of new technologies together with development in data communication benefited for rapid development. The author has been doing research as well as working with SHM and related tasks nearly a decade. Both theoretical knowledge and practical experience are gained in this constantly developing field. This doctoral thesis presents lessons learned in SHM and sensory technologies when monitoring civil engineering structures, mostly bridges. Nevertheless, these techniques can also be used in most applications related to civil engineering like dams, high rise buildings, off-shore platforms, pipelines, harbour structures and historical monuments. Emerging and established technologies are presented, discussed and examples are given based on the experience achieved. A special care is given to Fibre Optic Sensor (FOS) technology and its latest approach. Results from crack detection testing, long-term monitoring, and sensor comparison and installation procedure are highlighted. The important subjects around sensory technology and SHM are discussed based on the author's experience and recommendations are given. Applied research with empirical and experimental methods was carried out. A state-of-the art-review of SHM started the process but extensive literature studies were done continuously along the years in order to keep the knowledge up to date. Several SHM cases, both small and large scale, were carried out including sensor selection, installation planning, physical installation, data acquisition set-up, testing, monitoring, documentation and reporting. One case study also included modification and improvement of designed system and physical repair of sensors as well as two Site Acceptance Tests (SATs) and the novel crack detection system testing. Temporary measuring and testing also took place and numerous Structural Health Monitoring Systems (SHMSs) were designed for new bridges. The observed and measured data/phenomena were documented and analysed. Engineers, researchers and owners of structures are given an essential implement in managing and maintaining structures. Long-term effects like shrinkage and creep in pre-stressed segmental build bridges were studied. Many studies show that existing model codes are not so good to predict these long-term effects. The results gained from the research study with New Årsta Railway Bridge are biased be the fact that our structure is indeed special. Anyhow, the results can be compared to other similar structures and adequately used for the maintenance planning for the case study. A long-term effect like fatigue in steel structures is a serious issue that may lead to structural collapse. Novel crack detection and localisation system, based on development on crack identification algorithm implemented in DiTeSt system and SMARTape delamination mechanism, was developed, tested and implemented. Additionally, new methods and procedures in installing, testing, modifying and improving the installed system were developed. There are no common procedures how to present the existing FOS techniques. It is difficult for an inexperienced person to judge and compare different systems. Experience gained when working with Fibre Optic Sensors (FOS) is collected and presented. The purpose is, firstly to give advice when judging different systems and secondly, to promote for more standardised way to present technical requirements. Furthermore, there is need to regulate the vocabulary in the field. Finally, the general accumulated experience is gathered. It is essential to understand the complexity of the subject in order to make use of it. General trends and development are compared for different applications. As the area of research is wide, some chosen, specific issues are analysed on a more detailed level. Conclusions are drawn and recommendations are given, both specific and more general. SHMS for a complex structure requires numerous parameters to be measured. Combination of several techniques will enable all required measurements to be taken. In addition, experienced specialists need to work in collaboration with structural engineers in order to provide high-quality systems that complete the technical requirement. Smaller amount of sensors with proper data analysis is better than a complicated system with numerous sensors but with poor analysis. Basic education and continuous update for people working with emerging technologies are also obligatory. A lot of capital can be saved if more straightforward communication and international collaboration are established: not only the advances but also the experienced problems and malfunctions need to be highlighted and discussed in order not to be repeated. Quality assurance issues need to be optimized in order to provide high quality SHMSs. Nevertheless, our structures are aging and we can be sure that the future for sensory technologies and SHM is promising. The final conclusion is that an expert in SHM field needs wide education, understanding, experience, practical sense, curiosity and preferably investigational mind in order to solve the problems that are faced out when working with emerging technologies in the real world applications. The human factor, to be able to bind good relationship with workmanship cannot be neglected either. There is also need to be constantly updated as the field itself is in continuous development.
QC 20111117
SHMS of the New Årsta Railway Bridge

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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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Ulbricht, Andreas, Maik Gude, Daniel Barfuß, Michael Birke, Andree Schwaar, and Andrzej Czulak. "Potential and application fields of lightweight hydraulic components in multi-material design." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200294.

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Hydraulic systems are used in many fields of applications for different functions like energy storage in hybrid systems. Generally the mass of hydraulic systems plays a key role especially for mobile hydraulics (construction machines, trucks, cars) and hydraulic aircraft systems. The main product properties like energy efficiency or payload can be improved by reducing the mass. In this connection carbon fiber reinforced plastics (CFRP) with their superior specific strength and stiffness open up new chances to acquire new lightweight potentials compared to metallic components. However, complex quality control and failure identification slow down the substitution of metals by fiber-reinforced plastics (FRP). But the lower manufacturing temperatures of FRP compared to metals allow the integration of sensors within FRP-components. These sensors then can be advantageously used for many functions like quality control during the manufacturing process or structural health monitoring (SHM) for failure detection during their life cycle. Thus, lightweight hydraulic components made of composite materials as well as sensor integration in composite components are a main fields of research and development at the Institute of Lightweight Engineering and Polymer Technology (ILK) of the TU Dresden as well as at the Leichtbau-Zentrum Sachsen GmbH (LZS).

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Dissertations / Theses on the topic 'Fibre optic sensor networks'

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