Dissertations / Theses on the topic 'Distributed fibre optic sensor'
To see the other types of publications on this topic, follow the link: Distributed fibre optic sensor.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Distributed fibre optic sensor.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
MacLean, Alistair. "A distributed fibre optic water sensor." Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248853.
Full text
2
Kerrouche, Abdelfateh. "Fibre Optic Distributed Sensors Systems for Structural Health Monitoring." Thesis, City University London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.507411.
Full text
3
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.
Full textAbstract:
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.
4
Juarez, Juan C. "Distributed fiber optic intrusion sensor system for monitoring long perimeters." Thesis, [College Station, Tex. : Texas A&M University, 2005. http://hdl.handle.net/1969.1/ETD-TAMU-1702.
Full text
5
Zeng, Xiaodong. "Characterization and application of Brillouin scattering-based distributed fiber optic sensor." Thesis, University of Ottawa (Canada), 2003. http://hdl.handle.net/10393/26414.
Full textAbstract:
Brillouin scattering based distributed fiber optic sensing as a novel technique has attracted much attention in both research and application for the past ten years. The fiber optic group at the University of Ottawa has developed an advanced automatic Brillouin sensing system and improved it continuously. This thesis presents the characterization and optimization of this sensing system and a series of successful applications both in the laboratory and in the field.
Several parameters have been studied around the pulse generation subsystem: such as, bias, leakage, PW voltage, pulsewidth, and repetition frequency. Bias is found to be the most important parameter. We also discuss the relationships between the system repeatability and control parameters such as bias, polarization states, averages and frequency lock methods.
Four successful applications of the distributed Brillouin sensing system are reported in the thesis. They are strain measurement in a reinforced concrete beam, simultaneous strain and temperature monitoring of composite curing process, strain and temperature monitoring of a concrete structure, and temperature compensated strain measurement of the load test on the Rollinsford Bridge.
6
Baldwin, Christopher S. "Distributed sensing for flexible structures using a fiber optic sensor system." College Park, Md. : University of Maryland, 2003. http://hdl.handle.net/1903/288.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2003.Thesis research directed by: Mechanical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
7
Almutairi, Fajhan Hilal Hamad. "Fibre optic distributed temperature sensors applications and temperature modelling in intelligent wells environments." Thesis, Heriot-Watt University, 2007. http://hdl.handle.net/10399/63.
Full text
8
Sjölander, Ola. "Optimization and Miniaturization of a Fiber-Optic ф-OTDR Distributed Vibration Sensor." Thesis, KTH, Tillämpad fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231925.
Full text
9
Liu, Bo. "Sapphire Fiber-based Distributed High-temperature Sensing System." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/82741.
Full textAbstract:
From the monitoring of deep ocean conditions to the imaging and exploration of the vast universe, optical sensors are playing a unique, critical role in all areas of scientific research. Optical fiber sensors, in particular, are not only widely used in daily life such as for medical inspection, structural health monitoring, and environmental surveillance, but also in high-tech, high-security applications such as missile guidance or monitoring of aircraft engines and structures. Measurements of physical parameters are required in harsh environments including high pressure, high temperature, highly electromagnetically-active and corrosive conditions. A typical example is fossil fuel-based power plants. Unfortunately, current optical fiber sensors for high-temperature monitoring can work only for single point measurement, as traditional fully-distributed temperature sensing techniques are restricted for temperatures below 800°C due to the limitation of the fragile character of silica fiber under high temperature.
In this research, a first-of-its-kind technology was developed which pushed the limits of fully distributed temperature sensing (DTS) in harsh environments by exploring the feasibility of DTS in optical sapphire waveguides. An all sapphire fiber-based Raman DTS system was demonstrated in a 3-meters long sapphire fiber up to a temperature of 1400°C with a spatial resolution of 16.4cm and a standard deviation of a few degrees Celsius.
In this dissertation, the design, fabrication, and testing of the sapphire fiber-based Raman DTS system are discussed in detail. The plan and direction for future work are also suggested with an aim for commercialization.Ph. D.
10
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.
Full textAbstract:
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.
11
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.
Full textAbstract:
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
12
Huang, Zhengyu. "Quasi-Distributed Intrinsic Fabry-Perot Interferometric Fiber Sensor for Temperature and Strain Sensing." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/26247.
Full textAbstract:
The motivation of this research is to meet the growing demand for the measurand high-resolution, high-spatial resolution, attenuation insensitive and low-cost quasi-distributed temperature and strain sensors that can reliably work under harsh environment or in extended structures. There are two main drives for distributed fiber sensor research. The first is to lower cost-per-sensor so that the fiber sensors may become price-competitive against electrical sensors in order to gain widespread acceptance. The second is to obtain spatial distribution of the measurand.
This dissertation presents detailed research on the design, modeling, analysis, system implementation, sensor fabrication, performance evaluation, sensor field test and noise analysis of a quasi-distributed intrinsic Fabry-Perot interferometric (IFPI) fiber sensor suitable for temperature and strain measurement. For the first time to our knowledge, an IFPI sensor using a different type of fiber spliced in between two single-mode fibers is proposed and tested. The proposed sensor has high measurement accuracy, excellent repeatability, a large working range and a low insertion-loss. It requests no annealing after the sensor is made, and the sensor is calibration-free. The sensor fabrication is low-cost and has a high yield rate. The goal for this research is to bring this sensor to a level where it will become commercially viable for quasi-distributed sensing applications.Ph. D.
13
Newman, Jason. "A FIBER SENSOR INTEGRATED MONITOR FOR EMBEDDED INSTRUMENTATION SYSTEMS." International Foundation for Telemetering, 2006. http://hdl.handle.net/10150/604111.
Full textAbstract:
ITC/USA 2006 Conference Proceedings / The Forty-Second Annual International Telemetering Conference and Technical Exhibition / October 23-26, 2006 / Town and Country Resort & Convention Center, San Diego, CaliforniaIn this paper we will present a new fiber sensor integrated monitor (FSIM) to be used in an embedded instrumentation system (EIS). The proposed system consists of a super luminescent diode (SLD) as a broadband source, a novel high speed tunable MEMS filter with built in photodetector, and an integrated microprocessor for data aggregation, processing, and transmission. As an example, the system has been calibrated with an array of surface relief fiber Bragg gratings (SR-FBG) for high speed, high temperature monitoring. The entire system was built on a single breadboard less than 50 cm² in area.
14
Wang, Zhuang. "Intrinsic Fabry-Perot Interferometric Fiber Sensor Based on Ultra-Short Bragg Gratings for Quasi-Distributed Strain and Temperature Measurements." Diss., Virginia Tech, 2006. http://hdl.handle.net/10919/30213.
Full textAbstract:
The health monitoring of smart structures in civil engineering is becoming more and more important as in-situ structural monitoring would greatly reduce structure life-cycle costs and improve reliability. The distributed strain and temperature sensing is highly desired in large structures where strain and temperature at over thousand points need to be measured simultaneously. It is difficult to carry out this task using conventional electrical strain sensors. Fiber optic sensors provide an excellent opportunity to fulfill this need due to their capability to multiplex many sensors along a single fiber cable. Numerous research studies have been conducted in past decades to increase the number of sensors to be multiplexed in a distributed sensor network.
This dissertation presents detailed research work on the analysis, design, fabrication, testing, and evaluation of an intrinsic Fabry-Perot fiber optic sensor for quasi-distributed strain and temperature measurements. The sensor is based on two ultra-short and broadband reflection fiber Bragg gratings. One distinct feature of this sensor is its ultra low optical insertion loss, which allows a significant increase in the sensor multiplexing capability. Using a simple integrated sensor interrogation unit and an optical spectrum based signal processing algorithm, many sensors can be interrogated along a single optical fiber with high accuracy, high resolution and large dynamic range. Based on the experimental results and theoretical analysis, it is expected that more than 500 sensors can be multiplexed with little crosstalk using a frequency-division multiplexing technology. With this research, it is possible to build an easy fabrication, robust, high sensitivity and quasi-distributed fiber optic sensor network that can be operated reliably even in harsh environments or extended structures.
This research was supported in part by U.S. National Science Foundation under grant CMS-0427951.Ph. D.
15
Motúz, Rastislav. "Využití a potlačování dvojlomných jevů v optovláknových senzorických aplikacích." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2019. http://www.nusl.cz/ntk/nusl-409092.
Full textAbstract:
The thesis deals with integral and distributed optical fiber sensors of electric current. In the area of integral sensors the analysis is performed by Jones matrix calculus and the simultaneous influence of induced circular and undesired linear birefringence using an ortho-conjugation retroreflector. Furthermore, the proposed conjugation loop variant using half-wave phase retarders is analyzed. The theoretical conclusions are confirmed by simulation and experimental measurement. In the field of distributed fiber optic sensors, analysis and simulation for the detection of plasma currents in thermonuclear fusion reactors, based on the POTDR technique, is performed. An improvement procedure is proposed for circular-shaped vacuum vessel reactors. Plasma current detection procedure in divertor-type reactors have been newly designed and simulated to investigate the effect of the OTDR detector noise on plasma current detection accuracy.
16
Sikora, Vojtěch. "Zpracování signálů z optovláknových senzorů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377123.
Full textAbstract:
First two chapters of this paper deals with the division of optical fiber sensors, digital signal processing and includes price comparison of four experimental sensors. In chapter three analysis, description and evaluation of measurment has been demonstrated on Mach - Zehnder interferometer. Last chapter is about application for signal analysis from vibration sensors. Description contains snippets from source code and graphical user interface. This paper includes three fields - fiber optics, digital signal processing and creation of application - and thanks to them it provides solid basis for study of optic fiber sensors.
17
Harold, Douglas A. "An Evaluation of Optical Fiber Strain Sensing for Engineering Applications." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/41239.
Full textAbstract:
A fatigue test has been performed on 7075-T651 aluminum specimens which were bonded with polyimide coated optical fibers with discrete Bragg gratings. These fibers were bonded with AE-10 strain gage adhesive. The results indicate that lower strain amplitudes do not produce cause for concern, but that larger strain amplitudes (on the order of 3500 μ) may cause some sensors to become unreliable.
The strain response of acrylate coated optical fiber strain sensors bonded to aluminum specimens with AE-10 and M-Bond 200 strain gage adhesives was investigated with both axial and cantilever beam tests. These results were compared to both the strain response of conventional strain gages and to model predictions. The results indicate that only about 82.6% of the strain in the specimen was transferred through the glue line and fiber coating into the fiber. Thus, multiplying by a strain transfer factor of approximately 1.21 was sufficient to correct the optical fiber strain output. This effect was found to be independent of the adhesive used and independent of the three-dimensional profile of the glue line used to attach the fiber. Finally, this effect did not depend on whether the fiber had a polyimide or an acrylate coating.
Further investigation was conducted on the feasibility of using optical fiber strain sensors for monitoring subcritical damage (such as matrix cracks) in fiber reinforced composite materials. These results indicate that an array of optical fibers which monitor the strain profile on both sides of a composite panel may be sufficient for these purposesMaster of Science
18
VERGORI, ELENA. "Li-ion batteries monitoring for electrified vehicles applications." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2839860.
Full text
19
Holík, Tomáš. "Distribuované optické vláknové senzory." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377017.
Full textAbstract:
The thesis deals with the possibility of using optical fiber as a sensor. The introduction of the thesis is devoted to the foundations of optics. In addition, the thesis deals with optical interferometry, polarization and dispersion in optical fiber. The main output of the thesis is the comparison of acoustic vibration measurements using interferometric and polarization methods and further measurements on the real route in Brno.
20
Piccioni, Flavio. "Numerical Evaluation of Mode II Disbonding on Fiberglass CCPs-Specimens and Material Characterization Utilizing a Distributed Sensing Rayleigh Backscattering System." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/19848/.
Full textAbstract:
Nowadays, composite materials have become the main construction materials for aeronautical structures, replacing traditional materials commonly used in this industry. However, composite structures are still characterized by conservative designs due to the lack of understanding from a physics-based approach their damage propagation and failure mechanisms. Since repairs of composite structures are a crucial part of the long-term use of composites in aerospace, the stakeholders require an in depth understanding of the physics of disbonding in composites. The aim of this research is a numerical evaluation of mode II disbonding on Center Cut Plies (CCPs) specimens with a preliminary study on material characterization performed through a Distributed Sensing System (DSS). In order to fulfill the objectives of this research, CCPs specimens manufactured from unidirectional fiber prepregs will be considered. The specimens will be produced from unidirectional prepregs in order to minimize the effects of residual stress fields introduced into the specimen during the curing process. That residual stress field will be evaluated and monitored making use of a Distributed Sensing System (DSS) optical fiber mounted and embedded within the laminas of the specimen. In addition, an analytical and numerical approach through FEM analysis will be adopted and validated to verify the experimental results obtained from the DSS.
21
Ludden, Brendan Patrick. "A distributed optical fibre sensor." Thesis, University of Cambridge, 1997. https://www.repository.cam.ac.uk/handle/1810/272327.
Full text
22
Liang, Yuanxin. "Respiration monitoring with a fibre optic sensor." Swinburne Research Bank, 2008. http://hdl.handle.net/1959.3/47121.
Full textAbstract:
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.
23
Wang, Yunjing. "Fiber-Optic Sensors for Fully-Distributed Physical, Chemical and Biological Measurement." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/19222.
Full textAbstract:
Distributed sensing is highly desirable in a wide range of civil, industrial and military applications. The current technologies for distributed sensing are mainly based on the detection of optical signals resulted from different elastic or non-elastic light-matter interactions including Rayleigh, Raman and Brillouin scattering. However, they can measure temperature or strain only to date. Therefore, there is a need for technologies that can further expand measurement parameters even to chemical and biological stimuli to fulfill different application needs. This dissertation presents a fully-distributed fiber-optic sensing technique based on a traveling long-period grating (T-LPG) in a single-mode fiber. The T-LPG is generated by pulsed acoustic waves that propagate along the fiber. When there are changes in the fiber surrounding medium or in the fiber surface coating, induced by various physical, chemical or biological stimuli, the optical transmission spectrum of the T-LPG may shift. Therefore, by measuring the T-LPG resonance wavelength at different locations along the fiber, distributed measurement can be realized for a number of parameters beyond temperature and strain.
Based on this platform, fully-distributed temperature measurement in a 2.5m fiber was demonstrated. Then by coating the fiber with functional coatings, fully-distributed biological and chemical sensing was also demonstrated. In the biological sensing experiment, immunoglobulin G (IgG) was immobilized onto the fiber surface, and the experimental results show that only specific antigen-antibody binding can introduce a measurable shift in the transmission optical spectrum of the T-LPG when it passes through the pretreated fiber segment. In the hydrogen sensing experiment, the fiber was coated with a platinum (Pt) catalyst layer, which is heated by the thermal energy released from Pt-assisted combustion of H2 and O2, and the resulted temperature change gives rise to a measurable T-LPG wavelength shift when the T-LPG passes through. Hydrogen concentration from 1% to 3.8% was detected in the experiment. This technique may also permit measurement of other quantities by changing the functional coating on the fiber; therefore it is expected to be capable of other fully-distributed sensing applications.
Ph. D.
24
Froggatt, Mark E. "Distributed fiber-optic strain and temperature sensors using photoinduced bragg gratings." Thesis, Virginia Tech, 1995. http://hdl.handle.net/10919/41902.
Full textAbstract:
Much of the analytical and computational work necessary for the development of distributed fiber-optic strain sensors using photo induced Bragg gratings is presented. The one dimensional wave equation is solved for a slowly varying sinusoidal modulation of the index of refraction. The solution is found to take the form of a fourier transform for low reflectivity «15%) gratings. As a result, the process can be inverted, and if the phase and amplitude of the reflected light can be measured over frequency, the phase and amplitude of the bragg grating as a function of length can be computed using the inverse fourier transform. These results are computationally verified, and then further analysis of critical engineering parameters is carried out. A measurement system and procedure are described. A method of writing long, low-reflectivity bragg grating is proposed.
Master of Science
25
Xu, Xiaohua. "Dual Processing Spatially Distributed Integrating Fiber Optic Sensors for Non-intrusive Patient Monitoring." Master's thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/37093.
Full textAbstract:
Given the rapid aging of the worldâ s population, improvements in technology for automation of patient care and documentation are badly needed. This project is based on previous research that demonstrated a â smartâ bed that can non-intrusively monitor a patient in bed and determine a patient's respiration, heart rate and movement without intrusive or restrictive medical measurements. The â smartâ bed is an application of spatially distributed integrating fiber optic sensors. The basic concept is that any patient movement that also moves an optical fiber within a specified area will produce a change in the optical signal. A statistical mode (STM) sensor and a high order mode excitation (HOME) sensor were previously investigated, based on which the author developed the present design including both modal modulation approaches. Development was made in both hardware and software for the combined STM/HOME sensor: a special lens system was installed allowing only the high order modes of the optical fiber to be excited and coupled into the sensor; computer-processing method was used for handling output from the dual STM-HOME sensor, which would offer comprehensive perturbation analysis for more reliable patient monitoring. Experimental results of simulating human body breathing and heartbeats by periodic mechanical perturbations are also presented, and the relative advantage and drawbacks of the two modal modulation approaches are discussed.Master of Science
26
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.
Full text
27
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.
Full text
28
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.
Full text
29
de, Souza Keith R. C. P. "Fibre-optic distributed sensing based on spontaneous Brillouin scattering." Thesis, University of Southampton, 1999. https://eprints.soton.ac.uk/351507/.
Full textAbstract:
This thesis reports on the use of spontaneous Brillouin scattering for the purpose of fibre-optic distributed temperature and strain sensing based on a time-domain Landau-Placzek ratio technique. Detection system specifications are dictated by the spatial resolution, range, measurand resolution and measurement time. Pulsed sources are used in these sensors. The minimum spatial resolution depends on both the pulse width and receiver bandwidth. The range and measurand resolution depend on the peak pulse power launched into the sensing fibre as well as the Brillouin signal-to-noise characteristics at the receiver. The maximum launched pulse power is limited by the onset of nonlinear effects in the sensing fibre. Novel interferometric techniques based on low-cost, low loss all fibre Mach-Zehnder interferometric optical filters needed to separate the backscattered Rayleigh and spontaneous Brillouin signals have been developed with enhanced signal-to-noise capabilities. Used in conjunction with a newly developed low noise optical preamplifier /transimpedance receiver system, a distributed temperature sensor having 1.8m spatial resolution, 6.3 °C temperature resolution and a range of 23km is demonstrated. The strain dependence of the spontaneous Brillouin intensity has been determined. This coefficient is crucial for the development of a distributed temperature only sensor and /or a combined distributed temperature and strain sensor. Pulsed narrowband and broadband sources are necessary for resolving the Rayleigh and Brillouin signals as well as reducing coherent Rayleigh noise. The latter has been investigated and its dependence on certain parameters confirmed. A source capable of switching between narrowband and broadband operation has been demonstrated and is particularly appropriate for extended periods of data collection cycles.
30
MacPherson, William Neil. "Fibre optic sensors for applications in turbomachinery research." Thesis, Heriot-Watt University, 1999. http://hdl.handle.net/10399/585.
Full text
31
Wait, Peter Collinson. "The application of Brillouin scattering to distributed fibre optic sensing." Thesis, University of Southampton, 1997. https://eprints.soton.ac.uk/394568/.
Full textAbstract:
This thesis reports on an investigation into the application of Brillouin scattering for the purpose of distributed fibre optic sensing. The main focus of the work has been centred on a Brillouin optical time domain reflectometer (BOTDR) system. The behaviour of short (3m), medium (60m) and long (6km) erbium doped fibre amplifiers using narrow bandwidth pulsed signals has been investigated and the most suitable configuration for the source requirement of the BOTDR identified. The operation of a (BOTDR) system has been demonstrated at the low loss window of 1.5µm wavelength. Multiple Stokes orders of stimulated Brillouin scattering in a medium length erbium doped fibre amplifier using pulsed excitation are reported. The observed stimulated Brillouin threshold power is significantly reduced as a result of optical gain. The points of origin within the fibre of the generated Stokes pulses are located using space-time diagrams and are observed to depend on the Brillouin and Erbium pump powers. This has therefore been identified as a possible mechanism for sensing applications utilizing the novel technique of varying the pump powers to spatially interrogate the fibre. Measurements of the Brillouin scattering coherence length in silica fibre using a fibre Mach Zehnder interferometer are presented. As the Brillouin pump power is increased from below to above stimulated threshold, the line shape narrows and changes from that of a Lorentzian to a Gaussian. It is also shown that the Brillouin bandwidth approaches a limiting value. It is shown experimentally that the ratio of the intensities of Rayleigh and Brillouin backscattered light (Landau Placzek ratio) in an optical fibre has a temperature dependence which may be used for the basis of a distributed temperature sensor. This result, combined with the known frequency dependence of the Brillouin backscattering on temperature and strain, indicates spontaneous Brillouin backscatter may be used for the unique determination of either temperature or strain in a distributed fibre optic sensing system. Because of the coherent nature of Rayleigh scattering, use of the same narrow bandwidth source as required for the Brillouin signal in the Landau Placzek ratio method, results in significant coherent noise in the Rayleigh signal. A novel technique is demonstrated whereby the amplified spontaneous emission noise and amplifying properties of an erbium doped fibre amplifier may be exploited to reduce the coherent noise on the Rayleigh backscatter signal. This results in a significant improvement in both temperature and spatial resolution.
32
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.
Full text
33
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/.
Full textAbstract:
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.
34
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/.
Full textAbstract:
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.
35
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/.
Full textAbstract:
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.
36
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.
Full text
37
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.
Full text
38
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.
Full text
39
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/.
Full textAbstract:
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.
40
Liu, Xuan. "Characterization of Brillouin Scattering Spectrum in LEAF Fiber." Thèse, Université d'Ottawa / University of Ottawa, 2011. http://hdl.handle.net/10393/20474.
Full textAbstract:
Fiber optic sensors are designed to measure various parameters. The distributed fiber optics sensor has been a very promising candidate for the structural health monitoring. In this thesis, we characterized LEAF (Large Effective Area Fiber) fiber’s Brillouin scattering spectrum and investigated its potentiality for the distributed Brillouin temperature and strain sensor.
Optical fibers with complex refractive index profiles are applied to improve the Brillouin threshold by varying the Brillouin linewidth. As LEAF fiber has a modified refractive index profile, we investigated its Brillouin linewidth’s dependence on the square of the pump light’s frequency. We verified the Brillouin frequency’s variation with input SOP experimentally for LEAF fiber in the spontaneous regime. This sets a limitation for the frequency resolution of distributed Brillouin sensors. We also realized a simultaneous temperature and strain sensor with LEAF fiber applying the Brillouin optical time domain analysis. Based on the direct detection of LEAF beat frequencies, a simultaneous strain and temperature sensor was demonstrated.
41
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.
Full text
42
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.
Full text
43
Wang, Haichao. "A fibre optic system for distributed temperature sensing based on raman scattering." Thesis, University of Bradford, 2012. http://hdl.handle.net/10454/5498.
Full textAbstract:
This thesis is based on a research project to monitor the temperature profile along a power cable using the fibre optic Distributed Temperature Sensing (DTS) technology. Based on the temperature measured by a DTS system, real time condition monitoring of power cables can be achieved.
In this thesis, there are three main research themes.
1. Develop a DTS system for industrial applications. The entire hardware system and measuring software are developed to be an industrial product. Multiple functions are provided for the convenience of users to conduct temperature monitoring, temperature history logging and off-line simulation.
2. Enhance the robustness of the DTS system. An algorithm for signal compensation is developed to eliminate the signal fluctuation due to disturbance from the hardware and its working environment. It ensures robustness of the system in industrial environments and applicability to different system configurations.
3. Improve the accuracy of the DTS system. A calibration algorithm based on cubic spline fitting is developed to cope with non-uniform fibre loss in the system, which greatly improved the accuracy of the temperature decoding in real applications with unavoidable nonlinear
characteristics.
The developed DTS system and the algorithms have been verified by continuous experiments for about one year and achieved a temperature resolution of 0.1 degree Celsius, a spatial resolution of 1 meter, and a maximum error of 2 degree Celsius in an optic fibre with the length of 2910 metres.
44
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.
Full textAbstract:
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).
45
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.
Full text
46
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.
Full textAbstract:
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.
47
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/.
Full textAbstract:
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).
48
Iuliano, Marco. "Studio e caratterizzazione di sensori distribuiti in fibra ottica basati su scattering Brillouin." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13443/.
Full textAbstract:
Nel presente elaborato si mostra lo studio e la caratterizzazione di sensori distribuiti in fibra ottica (DOFS) basati sulla tecnica Brillouin Optical Time-Domain Analysis.
Si presenta una particolare implementazione ai sistemi BOTDA basati sulla modifica del BFRL (Brillouin Fiber Ring Laser) al fine di ottimizzarne la convenzionale configurazione per renderli economicamente vantaggiosi, permettendone un ampio
impiego e sviluppo su larga scala.
La sorgente BFRL presentata mostra degli adeguati valori di potenza del segnale di probe in uscita, un largo intervallo di modulazione ed una linewidth.
Essa permette quindi di ottenere un ottimo valore di risoluzione spaziale di 5 m per una fibra SMF della lunghezza di ~2.6 km, cui corrispondono i relativi valori di risoluzione di temperatura e strain rispettivamente di ~0.5°C e ~10 με.
49
Iqbal, Ahmer. "Heterojunction bipolar transistor based distributed amplifiers for fibre optic receiver front-end applications." Thesis, University of Manchester, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.734182.
Full text
50
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/.
Full text