To see the other types of publications on this topic, follow the link: Optical fiber sensor.
Dissertations / Theses on the topic 'Optical fiber 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 'Optical fiber 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
Wang, Xingwei. "Optical Fiber Tip Pressure Sensor." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/35490.
Full textAbstract:
Miniature pressure sensors which can endure harsh environments are a highly sought after goal in industrial, medical and research fields. Microelectromechanical systems (MEMS) are the current methods to fabricate such small sensors. However, they suffer from low sensitivity and poor mechanical properties.
To fulfill the need for robust and reliable miniature pressure sensors that can operate under high temperatures, a novel type of optical fiber tip sensor only 125μm in diameter is presented in this thesis. The essential element is a piece of hollow fiber which connects the fiber end and a diaphragm to form a Fabry-Pérot cavity. The all-fused-silica structure fabricated directly on a fiber tip has little temperature dependence and can function very well with high resolution and accuracy at temperatures up to 600ï °C. In addition to its miniature size, its advantages include superior mechanical properties, biocompatibility, immunity to electromagnetic interference, disposability and cost-effective fabrication.
The principle of operation, design analysis, fabrication implementation and performance evaluation of the sensor are discussed in detail in the following chapters.
Master of Science
2
Lee, Shiao-Chiu. "Axial offset effects upon optical fiber sensor and splice performance." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/91128.
Full textAbstract:
A kind of intensity modulated fiber sensor utilizing axial offset parameter is proposed. The theoretical analysis and experimental characteristics of this sensor are described.
All the theoretical results derived in this thesis are based on assuming a uniform power distribution in the fibers. An expression of coupling efficiency of central dipped parabolic graded index fibers due to axial offset is derived. The results show less sensitivity to axial offset for the central dipped fibers than for the parabolic profile fibers without a dip. Expressions of coupling efficiency of graded index fibers due to axial offset for several different values of a are also derived. The results show that sensitivity increases as the value of a decreases. A general expression of coupling efficiency which is valid for small values of axial offset is derived. This expression exhibits a linear relationship between coupling efficiency and small axial offset.
Coupling efficiencies versus fiber end separation and axial offset of step index fibers have been measured. The measurements show that coupling efficiency is much more sensitive to axial offset than end separation. A simple construction of the axial offset fiber sensor is described. An approximate linear relationship between the output power and the mechanical loading has been obtained for this sensor. Several ways of increasing the sensitivity of this sensor are discussed.M.S.
3
Bronk, Karen Srour. "Imaging based sensor arrays /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1996.
Find full textAbstract:
Thesis (Ph.D.)--Tufts University, 1996.Adviser: David R. Walt. Submitted to the Dept. of Chemistry. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;
4
Wavering, Thomas A. "Optical Path Length Multiplexing of Optical Fiber Sensors." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36037.
Full textAbstract:
Optical fiber sensor multiplexing reduces cost per sensor by designing a system that minimizes the expensive system components (sources, spectrometers, etc.) needed for a set number of sensors. The market for multiplexed optical sensors is growing as fiberoptic sensors are finding application in automated factories, mines, offshore platforms, air, sea, land, and space vehicles, energy distribution systems, medical patient surveillance systems, etc. Optical path length multiplexing (OPLM) is a modification to traditional white-light interferometry techniques to multiplex extrinsic Fabry-Perot interferometers and optical path length two-mode sensors. Additionally, OPLM techniques can be used to design an optical fiber sensor to detect pressure/force/acceleration and temperature simultaneously at a single point. While power losses and operating range restrictions limit the broadscale applicability of OPLM, it provides a way to easily double or quadruple the number of sensors by modifying the demodulation algorithm. The exciting aspect of OPLM is that no additional hardware is needed to multiplex a few sensors. In this way OPLM works with conventional technology and algorithms to drastically increase their efficiency. [1]Master of Science
5
Andrews, Jeffrey Pratt. "Longitudinal misalignment based strain sensor." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43283.
Full textAbstract:
A practical fiber optic strain sensor has been developed to measure strains in the range of 0.0 to 2.0 percent strain with a resolution ranging between 10 and 100 microstrain depending on sensor design choices. This intensity based sensor measures strain by monitoring strain induced longitudinal misalignment in a novel fiber interconnection. This interconnection is created by aligning fibers within a segment of hollow core fiber. Related splice loss mechanisms are investigated for their effect on resolution. The effect of gauge length and launch conditions are also investigated.
Master of Science
6
Chen, Qiao. "ESA based fiber optical humidity sensor." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/10134.
Full textAbstract:
Several techniques for measuring humidity are presented. The goal of the study is to use the electrostatic self-assembled monolayer synthesis process to fabricate a Fabry-Parot Cavity based optical fiber humidity sensor. The sensing scheme bases on the refractive index change with relative humidity of the film applied to the end of optical fiber. That is, the change in reflected optical power indicates certain humidity. To achieve this, some chemicals induce on specific coating materials were applied at the end of optical fiber. In this thesis, experimental results are given to prove that the humidity sensor has high sensitive and fast response time. Furthermore, we investigate the potential for the use of human breathing monitoring and air flow rate detection. Results from preliminary tests of each are given.Master of Science
7
Miller, Mark S. "Optical fiber-based corrosion sensor systems." Diss., This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-03042009-041455/.
Full text
8
Gaikwad, Parikshit S. "Chemically deposited optical fiber humidity sensor." Master's thesis, Mississippi State : Mississippi State University, 2003. http://library.msstate.edu/etd/show.asp?etd=etd-06092003-141607.
Full text
9
Fan, Chenjun. "Fiber optic sensor based on dual ring resonator system /." Online version of thesis, 1992. http://hdl.handle.net/1850/11070.
Full text
10
Ipson, Benjamin L. "Polarimetric Temperature Sensor Using Core-replaced Fiber." Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd606.pdf.
Full text
11
Beadle, Brad Michael. "Fiber optic sensor for ultrasound." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17869.
Full text
12
Beadle, Brad Michael. "Fiber optic sensor for ultrasound." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/19173.
Full text
13
Park, William Heuywon. "Fluorescence lifetime sensor using optical fiber and optical signal processing." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0009/MQ34107.pdf.
Full text
14
DeWolf, Scott. "Optical and mechanical behavior of the optical fiber infrasound sensor." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p1469578.
Full textAbstract:
Thesis (M.S.)--University of California, San Diego, 2009.Title from first page of PDF file (viewed October 22, 2009). Available via ProQuest Digital Dissertations. Includes bibliographical references (p. 46-48).
15
Kinney, Stuart. "The development of an optical position sensor." Virtual Press, 1998. http://liblink.bsu.edu/uhtbin/catkey/1115421.
Full textAbstract:
A theoretical study of an electrically passive, loss-compensated, optical position sensor is the goal of this project. Optical fiber sensors exploit light as the information carrier. Fiber-optic sensors consist of a constant light source launched into an optical fiber and transmitted to another point at which a measurement is made.In the proposed optical position sensor, a Light Emitting Diode (LED) produces a constant beam of light, which is channeled through an optical fiber to a Graded Index (GRIN) lens. This lens makes all the light rays parallel to one another, a process called collimation. The light then enters a polarizer which is a lens that further orders the light rays in a process called polarization.Then the light enters a chamber in which a doubly refracting (birefringent) crystal is situated. The crystal is a wedge, and thus has a varying thickness throughout its length. The light beam strikes the crystal, sending a spectrum, or spectral signature, that is distinct to the particular thickness of the crystal. That signature goes directly from the chamber housing the crystal into a lens called an analyzer which orders the light again through polarization. Then the light goes into another GRIN lens, and this GRIN lens focuses the light onto an optical fiber, which transmits the particular spectral signature of this light to an optical spectrum analyzer (OSA). The OSA uses a Photodiode Array to accept the incoming light, a device that takes in light and redistributes it to a monitor for display by the user. Such a device is called a detector. The thickness of the crystal that the light travels through is determined by the crystal's position.If the crystal rests on a platform which is connected to an object whose position must always be monitored, then the crystal will move as the object moves. The different spectral signatures shown on a monitor reveal different thicknesses of the crystal, which reveal different positions of the monitored object. The object whose position is measured is the measurand.The selected crystal is quartz. It has a 12.5-mm length, a width of 10.8-mm at its thinnest end, and a taper angle to the thickest end of only 0.008 degrees, which corresponds to a 0.17-micron difference between the two. This angle is called the polishing angle of the quartz. The quartz itself is called the active cell. The Photodiode Array Detector receives the spectral signature from the optical fiber, and that signature is projected on an OSA, which is software built-in to the computer. A mathematical program is used to evaluate the signature, and the position of the measurand is thereby revealed. How accurate the measurement is can be revealed by use of a control device. If the quartz crystal is moved by a measuring device, such as a micrometer, the distance that the crystal moved may be measured by the micrometer, as well as by the OSA. By comparing the two, the accuracy of the spectrograph, and the position it reveals, can be known.Department of Physics and Astronomy
16
Xiao, Hai. "Self-Calibrated Interferometric/Intensity-Based Fiber Optic Pressure Sensors." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/28845.
Full textAbstract:
To fulfill the objective of providing robust and reliable fiber optic pressure sensors capable of operating in harsh environments, this dissertation presents the detailed research work on the design, modeling, implementation, analysis, and performance evaluation of the novel fiber optic self-calibrated interferometric/intensity-based (SCIIB) pressure sensor system.
By self-referencing its two channels outputs, for the first time to our knowledge, the developed SCIIB technology can fully compensate for the fluctuation of source power and the variations of fiber losses. Based on the SCIIB principle, both multimode and single-mode fiber-based SCIIB sensor systems were designed and successfully implemented. To achieve all the potential advantages of the SCIIB technology, the novel controlled thermal bonding method was proposed, designed, and developed to fabricate high performance fiber optic Fabry-Perot sensor probes with excellent mechanical strength and temperature stability. Mathematical models of the sensor in response to the pressure and temperature are studied to provide a guideline for optimal design of the sensor probe. The solid and detailed noise analysis is also presented to provide a better understanding of the performance limitation of the SCIIB system. Based on the system noise analysis results, optimization measures are proposed to improve the system performance. Extensive experiments have also been conducted to systematically evaluate the performance of the instrumentation systems and the sensor probes. The major test results give us the confidence to believe that the development of the fiber optic SCIIB pressure sensor system provides a reliable pressure measurement tool capable of operating in high pressure, high temperature harsh environments.Ph. D.
17
Luanje, Appolinaire Tifang. "INTEGRATED OPTICAL FIBER RAMAN SENSOR FOR CRYOGENIC APPLICATION." MSSTATE, 2008. http://sun.library.msstate.edu/ETD-db/theses/available/etd-04042008-155057/.
Full textAbstract:
An integrated fiber optical Raman sensor was designed for real-time, non intrusive detection of liquid and gaseous mixtures at high pressure and high flow rates. The integrated sensor employs a high-power solid-state pumped Nd:YAG frequency doubled (532nm) laser (3W), a modified In Photonics Raman probe which has built-in Raman signal filter optics, and two high-resolution spectrometers and photomultiplier tubes (PMT) with selected bandpass filters to collect both N2 and O2 Raman signals. The detection unit was also integrated with Lab View software interfaced PMT modules for fast data acquisition.
18
Shreeve, Bryson J. "Magnetic Field Sensing with Slab Coupled Optical Fiber Sensors." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2774.
Full textAbstract:
This thesis reports an in-fiber magnetic field sensor that is able to detect magnetic fields as low as 2 A/m at a spatial resolution of 1 mm. The small sensor consists of a magneto-optic slab waveguide, bismuth-doped rare earth iron garnet (Bi-RIG) that is coupled to an optical fiber. By coupling light from the fiber to the slab waveguide, it becomes an in-fiber magnetic field sensor. This is due to the Magneto-Optic Kerr effect; a change in refractive index is proportional to the applied magnetic field. When an AC field is applied, an AC component in the output power can be detected by a spectrum analyzer. The novelties of Magneto-Optic Slab Coupled Optical Sensor (MO-SCOS) devices include their small compact nature and a dielectric structure allowing low electromagnetic interference. Due to their compact size they are capable of placement within devices to measure interior electromagnetic fields immeasurable by other sensors that are either too large for internal placement or disruptive of the internal fields due to metallic structure. This work also reports progress on EO SCOS development. The EO sensor has found application in new environments including the electromagnetic rail gun, and a dual-axis sensor.
19
Olson, Noah Gale 1969. "Mechanical and optical behavior of a novel optical fiber crack sensor and an interferometric strain sensor." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29259.
Full textAbstract:
Thesis (Ph. D .)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2002.Includes bibliographical references.
The proper interpretation of measurements from an optical fiber sensor requires a full understanding of its mechanical response to external action and the corresponding change in optical output. To quantify the mechanical behavior it is necessary to know the mechanical properties of the fiber coatings. A new method for measuring the coating stiffness directly on the fiber uses nano-indentation. Special sample preparation and testing procedures were developed for the measurement of very low modulus materials using the Nano Indenter II. Results are obtained for two different acrylate coated optical fibers, namely Corning SMF28 and 3M FS-SN-4228. These results are used in understanding the behavior of the novel crack sensor and of an interferometric strain sensor. A distributed crack sensor that does not require prior knowledge of crack location and employs a small number of fibers to monitor a large number of cracks is developed. The basic design of the sensor is a polymer sheet containing an inclined fiber that is coupled to a structure. The sensor principle is that cracking in the structural member leads to cracking in the polymer sheet which induces fiber bending leading to signal loss. Monitoring the backscattered signal provides crack opening size and location. A theoretical model for optical fiber loss prediction is developed based on a combination of mechanical and optical analyses.
(cont.) Model prediction is found to be in relatively close agreement with experimental results. Model simulation can hence be carried out to provide guidelines for designing crack sensors for various applications. The behavior of both coated and uncoated fibers for strain measurement applications is also examined. A theoretical assessment using a three-dimensional finite element model for both coated and uncoated optical fibers is presented. Results show that the coating stiffness can significantly affect the strain transfer from the member under load to the optical fiber. The three-dimensional finite element model can provide guidelines for the optimized design of strain sensors. A straightforward analytical solution shows good equivalence with the theoretical solution under certain conditions. Experiments using an interferometer were conducted to verify the results of the theoretical study and show good correspondence.
by Noah Gale Olson.
Ph.D .
20
Xu, Lina. "Optical fiber humidity sensor based on evanescent wave scattering." MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-07092004-112625/.
Full textAbstract:
An optical fiber humidity sensor has been devised using a porous sol-gel silica (PSGS) coating as a transducer. Evanescent wave scattering (EWS) in the PSGS coating. PSGS particles are highly hydrophilic and have a strong tendency to absorb water molecules from the surrounding environment. The absorbed water molecules form a thin layer on the inner surface of the pores inside the porous silica and enhance EWS, from which an indicatory signal can be obtained. The humidity sensor presented in this thesis has a fast response, is reversible, low cost, and has a broad dynamic relative humidity range from 3.6?0-6% to 100% or humidity range from 1.2ppm to 30000ppm. Because of its multiple advantages, including immunity to electromagnetic interference, resistance to corrosive environments, and high sensitivity, this humidity sensor has various applications. In soil moisture sensing, this humidity sensor can avoid the interference caused by compounds in soil water. For electrical transformer moisture sensing, this humidity sensor can avoid the effect of electromagnetic fields.
21
Qin, Zengguang. "Distributed Optical Fiber Vibration Sensor Based on Rayleigh Backscattering." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24105.
Full textAbstract:
This thesis includes studies of developing distributed optical fiber vibration sensor based on Rayleigh backscattering with broad frequency response range and high spatial resolution.
Distributed vibration sensor based on all-polarization-maintaining configurations of the phase-sensitive optical time domain reflectometry (OTDR) is developed to achieve high frequency response and spatial resolution. Signal fading and noise induced by polarization change can be mitigated via polarization-maintaining components. Pencil-break event is tested as a vibration source and the layout of the sensing fiber part is designed for real applications. The spatial resolution is 1m and the maximum distance between sensing fiber and vibration event is 18cm.
Wavelet denoising method is introduced to improve the performance of the distributed vibration sensor based on phase-sensitive OTDR in standard single-mode fiber. Noise can be reduced more effectively by thresholding the wavelet coefficient. Sub-meter spatial resolution is obtained with a detectable frequency up to 8 kHz.
A new distributed vibration sensor based on time-division multiplexing (TDM) scheme is also studied. A special probe waveform including a narrow pules and a quasi-continuous wave can combine the conventional phase-sensitive OTDR system and polarization diversity scheme together in one single-mode fiber without crosstalk. Position and frequency of the vibration can be determined by these two detection systems consecutively in different time slots. Vibration event up to 0.6 MHz is detected with 1m spatial resolution along a 680m single-mode sensing fiber.
Continuous wavelet transform (CWT) is investigated to study the non-stationary vibration events measured by our phase OTDR system. The CWT approach can access both frequency and time information of the vibration event simultaneously. Distributed vibration measurements of 500Hz and 500Hz to 1 kHz sweep events over 20 cm fiber length are demonstrated using a single-mode fiber.
Optical frequency-domain reflectometry (OFDR) for vibration sensing is proposed for the first time. The local Rayleigh backscatter spectrum shift in time sequence could be used to determine dynamic strain information at a specific position of the vibrated state with respect to that of the non-vibrated state. Measurable frequency range of 0-32 Hz with the spatial resolution of 10 cm is demonstrated along a 17 m fiber.
22
ROSAS, BRUNO PEREIRA. "OPTICAL FIBER SENSOR DISCRIMINATOR FOR JACKETED TANKS LEAKAGE DETECTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=4280@1.
Full textAbstract:
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOAGÊNCIA NACIONAL DE PETRÓLEO
A contaminação do solo nos postos de serviço é um risco ambiental associado à atividade de distribuição de derivados de petróleo que precisa ser controlado. O aumento deste risco está diretamente ligado à idade dos tanques e tubulações e à baixa qualidade na operação dos postos. Tais problemas vêm sendo minimizados ao longo das duas ultimas décadas graças à utilização de equipamentos mais modernos e das crescentes exigências ambientais. Nesta tese foi desenvolvido e testado em laboratório um equipamento de controle ambiental, baseado em tecnologia de sensores a fibra óptica, para a detecção de vazamentos em tanques jaquetados (dupla parede). A detecção de vazamentos neste tipo de tanque tornou-se uma exigência dos órgãos de proteção ambiental. O uso de tanques jaquetados com sistema de detecção permite que seja evitado o contato dos fluidos combustíveis com o solo, pois, uma vez rompida a parede interna de aço carbono do tanque, o sistema acusa a presença de hidrocarbonetos no interstício do tanque. Outrossim, a discriminação do fluido quando ocorrido o vazamento é importante para que se possa detectar mais facilmente se o rompimento se deu na parede interna ou externa do tanque, possibilitando um rápido diagnóstico e a conseqüente tomada de medidas corretivas do problema. Com a evolução legislativa no campo ambiental e o foco do Poder Público na garantia de uma maior qualidade de vida, o País está passando por um momento de transição onde, em um curto espaço de tempo, quase que 70 por cento dos tanques em operação deverão ser substituídos. Dessa feita, o equipamento para monitoramento ambiental desenvolvido nesta tese visa também tornar economicamente possível a substituição do atual parque de tanques por novos, já com sensores ópticos incorporados.
Soil contamination due to leakage of hydrocarbon fuels from tanks in service stations is an environmental risk associated with the distribution segment of the petroleum industry. Such risk is closely related to ageing tanks and piping systems, as well as to the lack of quality assurance practices in service stations. This problem is being reduced during the last two decades, mainly due to use of modern equipment that must adhere to more rigid environmental legislation. In this thesis, an optical fiber sensor, able to discriminate different liquids, has been developed as a part of a leakage detection system employed to monitor jacketed tanks used to store alcohol or hydrocarbon or fuels. Leakage detection in this type of storage tanks plays an important role to minimize problems due to soil contamination and is now required according to new environmental legislation. If fuel leaks through the carbon steel wall of jacketed tanks it will be contained, within an interstitial space, by the outer, fiber reinforced, polymeric wall of the tank. Presence of fluid in the interstitial space is monitored by the optical fiber sensor, which sends a warning to the service station operator, which immediately has to start maintenance procedures. The capability of discriminating different fuels will allow the operator to quickly identify from which tank compartment the leakage has originated, or, if water coming from the soil has been detected, that the outer wall of the tank has been damaged and needs to be repaired.
23
Garrett, Tracey Lynette. "Optical fiber sensor methods for nondestructive evaluation of bridges." Master's thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-03302010-020536/.
Full text
24
Cameron, Alexander John. "A Bayesian approach to optimal sensor placement." Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:ad201132-d418-4ee4-a9d5-3d79bd4876a7.
Full textAbstract:
By "intelligently" locating a sensor with respect to its environment it is possible to minimize the number of sensing operations required to perform many tasks. This is particularly important for sensing media which provide only "sparse" data, such as tactile sensors and sonar. In this thesis, a system is described which uses the principles of statistical decision theory to determine the optimal sensing locations to perform recognition and localization operations. The system uses a Bayesian approach to utilize any prior object information (including object models or previously-acquired sensory data) in choosing the sensing locations.
25
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
26
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
27
Ren, Yundong. "Specially Shaped Optical Fiber Probes: Understanding and Their Applications in Integrated Photonics, Sensing, and Microfluidics." Digital WPI, 2019. https://digitalcommons.wpi.edu/etd-dissertations/569.
Full textAbstract:
Thanks to their capability of transmitting light with low loss, optical fibers have found a wide range of applications in illumination, imaging, and telecommunication. However, since the light guided in a regular optical fiber is well confined in the core and effectively isolated from the environment, the fiber does not allow the interactions between the light and matters around it, which are critical for many sensing and actuation applications. Specially shaped optical fibers endow the guided light in optical fibers with the capability of interacting with the environment by modifying part of the fiber into a special shape, while still preserving the regular fiber’s benefit of low-loss light delivering. However, the existing specially shaped fibers have the following limitations: 1) limited light coupling efficiency between the regular optical fiber and the specially shaped optical fiber, 2) lack special shape designs that can facilitate the light-matter interactions, 3) inadequate material selections for different applications, 4) the existing fabrication setups for the specially shaped fibers have poor accessibility, repeatability, and controllability. The overall goal of this dissertation is to further the fundamental understanding of specially shaped fibers and to develop novel specially shaped fibers for different applications. In addition, the final part of this dissertation work proposed a microfluidic platform that can potentially improve the light-matter interactions of the specially shaped fibers in fluidic environments. The contributions of this dissertation work are summarized as follows: 1) An enhanced fiber tapering system for highly repeatable adiabatic tapered fiber fabrications. An enhanced fiber tapering system based on a novel heat source and an innovative monitoring method have been developed. The novel heat source is a low-cost ceramic housed electric furnace (CHEF). The innovative monitoring method is based on the frequency-domain optical transmission signal from the fiber that is being tapered. The enhanced fiber tapering system can allow highly repeatable fabrication of adiabatically tapered fibers. 2) A lossy mode resonance (LMR) sensor enabled by SnO2 coating on a novel specially shaped fiber design has been developed. The developed LMR sensor has a D-shape fiber tip with SnO2 coating. It has the capability of relative humidity and moisture sensing. The fiber-tip form factor can allow the sensor to be used like a probe and be inserted into/removed from a tight space. 3) Specially shaped tapered fibers with novel designs have been developed for integrated photonic and microfluidic applications. Two novel specially tapered fibers, the tapered fiber loop and the tapered fiber helix have been developed. The tapered fiber loop developed in this work has two superiority that differentiated itself from previous works: a) the mechanical stability of the tapered fiber loop in this work is significantly better. b) the tapered fiber loops in this work can achieve a diameter as small as 15 ?m while still have a high intrinsic optical quality factor of 32,500. The tapered fiber helix developed in this work has a 3D structure that allows it to efficiently deliver light to locations out of the plane defined by its two regular fiber arms. Applications of the tapered fiber helices in both integrated photonic device characterizations and microparticle manipulations have been demonstrated. 4) Developed an acrylic-tape hybrid microfluidic platform that can allow function reconfiguration and optical fiber integration. A low-cost, versatile microfluidic platform based on reconfigurable acrylic-tape hybrid microfluidic devices has been developed. To the best of the author’s knowledge, this is the first time that the fabrication method of sealing the acrylic channel with a reconfigurable functional tape has been demonstrated. The tape-sealing method is compatible with specially shaped fiber integrations.
28
Ren, Meiqi. "Distributed Optical Fiber Vibration Sensor Based on Phase-Sensitive Optical Time Domain Reflectometry." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34400.
Full textAbstract:
In this thesis, the work focuses on developing distributed optical fiber vibration sensors based on phase-sensitive optical time domain reflectometry (Φ-OTDR). Three works have been accomplished to improve the performances of Φ-OTDR for distributed vibration sensing. Firstly, Φ-OTDR based on a polarization diversity scheme is demonstrated to mitigate the polarization mismatch effect occurring in traditional systems. A theoretical analysis is performed in different polarization cases corresponding to coherent and polarization diversity detection. Φ-OTDR based polarization diversity shows a great potential in the multi-events sensing application. Two vibration events are simultaneously detected and their signal to noise ratios are improved by 10.9 dB and 8.65 dB, respectively, compared to the results obtained by a conventional coherent scheme.
Intensity fluctuation in a phase-sensitive optical-time domain reflectometry (Φ-OTDR) system caused by stochastic characteristics of Rayleigh backscattering has limited relative vibration strength measurement, which is proportional to dynamic strain. A trace-to-trace correlation coefficient is thus proposed to quantify the Φ-OTDR system stability and a novel approach of measuring the dynamic strain induced by various driving voltages of lead zicronate titanate (PZT) is demonstrated. Piezoelectric vibration signals are evaluated through analyzing peak values of the fast Fourier transform spectra at fundamental frequency and high-order harmonics based on Bessel functions. Experimental results show high correlation coefficients and good stability of our Φ-OTDR system, as well as the small measurement uncertainty of measured peak values.
To reduce the intra-band noise caused by the finite extinction ratio of optical pulses, Φ-OTDR based on high extinction ratio generation is studied. Two methods are developed for achieving high extinction ratio of optical pulse generation. One of the approaches is to synchronize two cascaded electro-optic modulators to achieve high extinction ratio operation. The other one is to use the nonlinear optical fiber loop mirror as an optical switch to suppress the continuous wave portion of optical pulse. The sensing range of 1.8 km and 8.4 km with corresponding spatial resolution of 0.5 m and 2 m have been demonstrated based on cascaded two electro-optic modulators and nonlinear optical fiber loop mirror setup, respectively.
29
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.
30
Shute, Marcus William Sr. "Polarization-maintaining optical fiber as a sensor of shell vibrations." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/17915.
Full text
31
Hu, Xue-Mei. "An optical fiber sensor for the determination of hydrogen peroxide." Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-04042008-123345.
Full text
32
Overby, Alan Bland. "Dissolved Gas Analysis of Insulating Transformer Oil Using Optical Fiber." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/48598.
Full textAbstract:
The power industry relies on high voltage transformers as the backbone of power distribution
networks. High voltage transformers are designed to handle immense electrical loads in hostile
environments. Long term placement is desired, however by being under constant heavy load
transformers face mechanical, thermal, and electrical stresses which lead to failures of the
protection systems in place. The service life of a transformer is often limited by the life time of
its insulation system. Insulation failures most often develop from thermal faults, or hotspots, and
electrical faults, or partial discharges. Detecting hotspots and partial discharges to predict
transformer life times is imperative and much research is focused towards these topics. As these
protection systems fail they often generate gas or acoustic signals signifying a problem. Research
has already been performed discovering new ways integrate optical fiber sensors into high
voltage transformers. This thesis is a continuation of that research by attempting to improve
sensor sensitivity for hydrogen and acetylene gasses. Of note is the fabrication of new hydrogen
sensing fiber for operation around a larger absorption peak and also the improvement of the
acetylene sensor's light source stability. Also detailed is the manufacturing of a field testable
prototype and the non-sensitivity testing of several other gasses. The developed sensors are
capable but still could be improved with the use of more powerful and stable light sources.Master of Science
33
BANO, ANDON. "Optical Fiber Sensors for Water Quality Monitoring." Doctoral thesis, Politecnico di Torino, 2021. http://hdl.handle.net/11583/2903506.
Full text
34
Xu, Ying. "Detection of delamination in composites with fiber optic sensor /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202004%20XU.
Full textAbstract:
Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 194-209). Also available in electronic version. Access restricted to campus users.
35
Kahn, Mohammed Tariq Ekeramodien. "Development of a non-monochromatic lightwave sensor for applications in smart structures research." Thesis, Peninsula Technikon, 1998. http://hdl.handle.net/20.500.11838/888.
Full textAbstract:
Thesis (MTech (Electrical Engineering))--Peninsula Technikon, Cape Town, 1998The purpose of this study was to perform an investigation into advances in the field of opto-electronics and to develop a suitable lightwave sensor, for application in smart structures research. Included in the scope of this research was the theoretical development and analysis of an appropriate technology to lead to an implementation of such sensors. This project forms part of an overall plan to gain experience in optoelectronic (photonic) sensor design. In research done previously in smart structure monitoring, piezo-electric techniques with the usual electrical interconnections was used. In a highly distributed sensor system the problems of electromagnetic interference, the tribo-electric effect and noise could be problematic. In this research, opto electronic techniques were thoroughly researched and an improvement on laser based fibre-optic interferometers was made. A non monochromatic lightwave interferometer was developed from theory and a prototype tested. The results suggests that an interferometric sensor can be operated with a non monochromatic source by using a second interferometer to modulate the frequency spectrum of the light before it is detected by a photodetector. Various test and measurement circuits for improved photodetector performance were evaluated, as well as a study of signal processing techniques that would be of use for an upgrade of the project where specific feature detection and analysis using the sensor is envisaged. A specification for a computer based data acquisition system was developed to do initial tests. The project should continue, with the sensor head being improved and all the necessary signal processing routines programmed into a Labview based data acquisition system.
36
Abeysinghe, Don Chandana. "Novel MEMS Pressure and Temperature Sensors Fabricated on Optical Fibers." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin997987327.
Full text
37
Furness, Charles Zachary. "Parameter identification of a flexible beam using a modal domain optical fiber sensor." Thesis, Virginia Tech, 1990. http://hdl.handle.net/10919/42058.
Full textAbstract:
An optical fiber sensor is used for identification of a cantilevered beam under conditions of various concentrated mass loadings. A model of the sensor as well as the dynamic system is developed and used to test the reliability of the identification. Input/output data from an experiment is gathered and used in the identification. A survey of the existing areas of damage detection and parameter identification is included, along with suggestions for incorporating fiber optic sensors into existing techniques. The goal of this research was to show that the fiber sensor can be used for identification purposes, and that it is sensitive to parameter changes within the system (in this case concentrated mass changes).
Master of Science
38
Scott, Brian Lee. "Fabrication and Characterization of a Porous Clad Optical Fiber Gas Sensor." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/30906.
Full textAbstract:
An optical fiber has been developed that can be used as a chemical gas sensor. Fabrication of the optical fiber produces a fiber that has a solid core with a porous cladding. The porous cladding region is made from a spinodally phase separable glass where the secondary phase is removed through dilute acid leaching. A non-phase separable glass composition is used for the core region. The properties of the phase separable glass are dependent on the processing conditions and the thermal history of the glass after the porosity has been achieved. Investigation of how processing conditions affected the pore structure was conducted to determine what pore characteristics are achievable for the glass composition used. Phase separation temperature, removal of silica gel deposited in the pores, and the post fabrication heat treating were used as experimental processing conditions. A maximum useable average pore size of approximately 29 nm was achieved. Maximum pore volume in the experimental groups was 0.4399 cc/g. Most heat treatments of the porous glass caused consolidation of the pore structure, with some conditions producing pore coarsening.Master of Science
39
Holmberg, Patrik. "Laser processing of Silica based glass." Doctoral thesis, KTH, Laserfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173929.
Full textAbstract:
The main topic of this thesis work is photosensitivity and photo-structuring of optical fibers and bulk glass. Although research in the field of photosensitivity in glass and optical fibers has been ongoing for more than three decades, the underlying mechanisms are still not well understood. The objective was to gain a better understanding of the photo-response by studying photosensitivity from a thermodynamic perspective, as opposed to established research focusing on point defects and structural changes, and strain and stress in optical fibers. Optical fibers was mainly used for experimental studies for two reasons; first, photosensitivity in fibers is more pronounced and more elusive compared to its bulk counterpart, and secondly, fibers provide a simplified structure to study as they experimentally can be seen as one-dimensional.Initially, ablation experiments on bulk glass were performed using picosecond infrared pulses. With a design cross section of 40x40 μm, straight channels were fabricated on the top (facing incident light) and bottom side of the sample and the resulting geometries were analyzed. The results show a higher sensitivity to experimental parameters for bottom side ablation which was ascribed to material incubation effects. Moreover, on the top side, the resulting geometry has a V-shape, independent of experimental parameters, related to the numerical aperture of the focusing lens, which was ascribed to shadowing effects.After this work, the focus shifted towards optical fibers, UV-induced fiber Bragg gratings (FBGs) and thermal processing with conventional oven and with a CO2 laser as a source of radiant heat.First, a system for CO2 laser heating of optical fibers was constructed. For measuring the temperature of the processed fibers, a special type of FBG with high temperature stability, referred to as "Chemical Composition Grating" (CCG) was used. A thorough characterization and temperature calibration was performed and the results show the temperature dynamics with a temporal resolution of less than one millisecond. The temperature profile of the fiber and the laser beam intensity profile could be measured with a spatial resolution limited by the grating length and diameter of the fiber. Temperatures as high as ~ 1750 °C could be measured with corresponding heating and cooling rates of 10.500 K/s and 6.500 K/s.Subsequently, a thorough investigation of annealing and thermal regeneration of FBGs in standard telecommunication fibers was performed. The results show that thermal grating regeneration involves several mechanisms. For strong regeneration, an optimum annealing temperature near 900 C was found. Two different activation energies could be extracted from an Arrhenius of index modulation and Braggv iwavelength, having a crossing point also around 900 °C, indication a balance of two opposing mechanisms.Finally, the thermal dynamics and spectral evolution during formation of long period fiber gratings (LPGs) were investigated. The gratings were fabricated using the CO2 laser system by periodically grooving the fibers by thermal ablation. Transmission losses were reduced by carefully selecting the proper processing conditions. These parameters were identified by mapping groove depth and transmission loss to laser intensity and exposure time.Huvudtemana i denna avhandling är fotokänslighet och fotostrukturering av optiska fibrer och bulk glas. Trots att forskning inom fotokänslighet i glas och optiska fibrer har pågått under mer än tre decennier är de bakomliggande mekanismerna ännu inte klarlagda. Syftet var att få en bättre förståelse för fotoresponsen genom att studera fotokäsligheten ur ett termodynamiskt perspektiv, i motsats till etablerad forskning med fokus på punktdefekter och strukturförändringar, samt mekaniska spännings effekter i optiska fibrer. Optiska fibrer användes för flertalet av de experimentella studierna av två skäl; för det första är fotokänsligheten i fibrer större och dessutom vet man mindre om bakomliggande mekanismer jämfört med motsvarande bulk glas, och för det andra kan fibrer vara enklare att studera eftersom de experimentellt kan ses som en endimensionell struktur.Inledningsvis utfördes ablaherings experiment på bulk glas med en infraröd laser med pikosekund pulser. Raka kanaler med ett designtvärsnitt på 40x40 μm tillverkades på ovansidan (mot infallande ljus) och bottensidan av provet och de resulterande geometrierna analyserades. Resultaten visar en högre känslighet för variationer i experimentella parametrar vid ablahering på undersidan vilket kan förklaras av inkubations effekter i materialet. Dessutom är den resulterande geometrin på ovansidan V-formad, oavsett experimentella parametrar, vilket kunde relateras till den numeriska aperturen hos den fokuserande linsen, vilket förklaras av skuggningseffekter.Efter detta arbete flyttades fokus mot optiska fibrer, UV inducerade fiber Bragg gitter (FBG), och termisk bearbetning med konventionell ugn samt även med en CO2-laser som källa för strålningsvärme.Först konstruerades ett system för CO2-laservärmning av fibrer. För mätning av temperaturen hos bearbetade fibrer användes en speciell sorts FBG med hög temperaturstabilitet, kallade ”Chemical Composition Gratings” (CCG). En grundlig karaktärisering och temperaturkalibrering utfördes och temperaturdynamiken mättes med en tidsupplösning på under en millisekund. Temperaturprofilen i fibern, och laserns strålprofil, kunde mätas med en spatiell upplösning begränsad av gitterlängden och fiberns diameter. Temperaturer upp till ~1750 °C, vilket är högre än mjukpunktstemperaturen, kunde mätas med korresponderande uppvärmnings- och avsvalningshastighet på 10.500 K/s och 6.500 K/s.Därefter gjordes en omfattande undersökning av värmebearbetning och termisk regenerering av FBG:er i telekomfiber. Resultaten visar att termisk gitter-regenerering aktiveras av flera olika mekanismer. Värmebearbetning vid en temperatur omkring 900 °C resulterade i starka gitter efter en regenerering vid en temperatur på 1100 °C. Två olika aktiveringsenergier kunde extraheras från en Arrhenius plot avseende brytningsindexmodulation och Braggvåglängd, med en skärningspunkt tillika runt 900 °C, vilket indikerar en avvägning mellan två motverkande mekanismer vid denna temperatur.Slutligen undersöktes temperaturdynamiken och de spektrala egenskaperna under tillverkning av långperiodiga fibergitter (LPG). Gittren tillverkades med CO2-vi iilasersystemet genom att skapa en periodisk urgröpning medelst termisk ablahering. Transmissionsförluster kunde reduceras med noggrant valda processparametrar. Dessa parametrar identifierades genom mätningar av ablaherat djup och transmissionsförlust som funktion av laserintensitet och exponeringstid.
QC 20150924
40
Hill, William Cary. "Low Modal Volume Single Crystal Sapphire Optical Fiber." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/78792.
Full textAbstract:
This research provides the first known procedure for cleanly and consistently reducing the diameter of single-crystal sapphire optical fiber (SCSF) below the limits of standard production methods, including the first production of subwavelength-diameter optical fiber (SDF) composed of single-crystal sapphire. The first known demonstration of an air-clad single crystal sapphire optical fiber demonstrating single-mode behavior is also presented, and the single-mode cutoff wavelength and diameter are determined.
Theoretical models describing and predicting the optical behavior of low modal volume sapphire optical fibers are also presented. These models are built upon standard weakly-guiding optical fiber theory, which is found to be accurate once experimentally-determined properties of the SCSF are substituted for theoretical values.
Reduced modal dispersion is also observed in the form of decreased laser pulse broadening in reduced-diameter SCSF. The improvements in spatial resolution for distributed sensing systems such as Raman distributed temperature sensing are also predicted based on the measured decrease in pulse duration.
This research also provides an enhanced understanding of the etching behavior of sulfuric and phosphoric acids on sapphire surfaces, including the first reporting of etching rates and activation energies for a-plane sapphire surfaces. Morphological changes of sulfuric and phosphoric acids at and beyond the temperature ranges used in etching were also tested and discussed in detail, especially regarding their practical impact on observed etching behavior.
The demonstration of LMV single-crystal sapphire optical fibers enables the adaptation of numerous sensing schemes requiring low modal volume or single-mode behavior to be utilized in extreme environments.Ph. D.
41
Garcia, Mina Diego Felipe. "Bi-tapered Fiber Sensor Using a Supercontinuum Light Source for a Broad Spectral Range." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1492001857501804.
Full text
42
Hernandez, Felipe Bueno. "Sensor de força utilizando Fiber taper." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18149/tde-27072016-074912/.
Full textAbstract:
Este trabalho teve por objetivo desenvolver e caracterizar um sensor de força utilizando uma fibra óptica modificada pelo processo conhecido como Fiber tapering. A fibra quando modificada deixa exposto o campo evanescente, o que a torna sensível a influências externas, e a luz guiada na fibra pode vir a sofrer reflexão interna total frustrada ao entrar em contato com materiais. Ao envolver a região modificada por um material elastomérico, a área de contato e consequentemente a atenuação torna-se uma função da intensidade da força aplicada, possibilitando então relacionar a força a atenuação da luz. Baseando-se nesse efeito, foi criado um sensor de dimensões reduzidas, de rápida resposta, linear, altamente sensível e de boa repetibilidade. Foi criado também um circuito eletrônico utilizando amplificadores operacionais para a aquisição e processamento do sinal proveniente da fibra e selecionado um sensor comercial comum para a realização de experimentos e comparações. Ambos os sensores foram posicionados sobre uma balança de precisão e submetidos a diversos esforços obtendo-se dados sobre a resposta estática. Em seguida utilizando um shaker eletrodinâmico foram medidos os tempos de resposta a uma entrada degrau, e realizando esforços repetitivos foram analisados os desvios das medidas lidas pelos sensores.The aim of this research was to develop and characterize a force sensor using a modified optical fiber by a process known as Fiber tapering. The modified fiber leaves the evanescent field exposed and prone to external influences and the guided light may suffer frustration of total internal reflection upon contact with materials. When covering the modified fiber section with an elastomeric material, the contact area and therefore the attenuation becomes a function of the applied pressure, making it possible to relate force to attenuation in light intensity. Based on this effect, a small sensor was created, having a quick response time, with high linearity, high sensitivity and good repeatability. Along with the sensor, an electronic circuit using operational amplifiers was designed for acquisition and processing of the signal obtained from the optical fiber. In addition, in order to perform experiments and comparisons, a standard force sensor was chosen. Both sensors were placed over a precision weighing scale and had different intensities of force applied on them, and after that, data regarding static measurements was gathered. The response time was obtained using an electrodynamic shaker and applying a step input. Furthermore, data was gathered about the deviations on the measurements by performing a repetitive set of compressions.
43
Wojcik, Aleksander Karol. "Signal statistics of phase dependent optical time domain reflectometry." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4873.
Full textAbstract:
The statistics of the phase dependent optical time-domain reflectometer have
been analyzed. The optical fiber is modeled by the use of a discrete set of reflectors
positioned randomly along the fiber. The statistics of the reflected light from
a traveling pulse are derived. The statistics of the signal are used to calculate the
characteristics of shot noise in the photodetector, and the probability that noise of
certain intensity will occur. An estimation of the backscattered power is made by calculating
the fraction of the backscattered power that is captured in a guiding mode.
Upper power limits are calculated by considering nonlinear optical effects. An estimation
of noise from thermally excited sound waves, amplified by Brillouin scattering,
is derived. This noise considers the parameters of a photodetector, giving a model
for the noise in the measurable photocurrent. Two models are used to describe the
fading probability of the signal. The first model, based on the Fabry-Perot interferometer
with a random phase perturbation in the middle, is used to calculate the
probability that the whole signal vanishes for any value of phase perturbation. The
second model, by calculating the correlation between two signals, one perturbed and
one unperturbed, predicts the fading of the signal of interest. The present work gives
the theoretical basis for the phase dependant Optical Time Domain Reflectometry,
allowing its optimization and setting the fundamental limitations to the performance of the system.
44
Johnson, Eric K. "Low Loss Hybrid Waveguide Electric Field Sensor Based on Optical D-fiber." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2153.pdf.
Full text
45
Tipparaju, Venkata Satya Sai Sarma. "An active core fiber optic gas sensor using a photonic crystal hollow core fiber as a transducer." Master's thesis, Mississippi State : Mississippi State University, 2007. http://sun.library.msstate.edu/ETD-db/theses/available/etd-06262007-164352/.
Full text
46
Marshall, Heather K. "Design of a biomimetic acoustic sensor." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/16085.
Full text
47
"Some applications of optical fibre sensor." Chinese University of Hong Kong, 1989. http://library.cuhk.edu.hk/record=b5886613.
Full text
48
Yu-lin, Fang, and 方友霖. "Polarization optical fiber sensor." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/k5r32j.
Full textAbstract:
博士國立高雄科技大學
機械工程系
107
This study proposes a multi-functional lab and used the principles of polarization light, long period fiber grating (LPFG) along with inductive couple plasma-Etcher to develop a POL-NLPFG lab on fiber sensor for strain. Using the POL-NLPFG sensors to detect the variations of the longitudinal loading. According to the results of the experiments, finding that the longitudinal loading are strengthen, the phenomenon of the transmission loss agrees with the coupled-mode theory and the dips of transmission loss performance a function of cosine. The sensor that execute the experiment of the axial loading test for more times to ensure the feasibility and reproducibility of the proposed optical fiber sensors. An Polarization u-shaped optical sensor that used alkylation technology to immobilize MiRNA-133a had be used to detect Mahlavu at concentrations 0.133 ng/ml-0.064 ng/ml was added to test the sensor. The results showed that the highest Mahlavu sensitivity of the Polarization U-shaped optical sensor spectral wavelength was-633.94 nm/% and linearity was 0.998. The results of the experiments indicated that the Polarization U-shaped optical sensor refractive index changed as Mahlavu concentrations increased, altering the coupling coefficient and causing linear changes in wavelength or transmission loss. These experiments verified that the Polarization U-shaped sensors developed in this study can be used as multi-functional lab on fiber sensing elements.
49
CHEN, JUN-YI, and 陳俊逸. "Improved Optical Fiber pH Sensor." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/pyzzk5.
Full textAbstract:
碩士銘傳大學
電子工程學系碩士班
104
PH value is used to specify the acidity or basicity of an aqueous solution because many biological and chemical reactions depend on suitable pH value. PH sensors are widely used in chemical plants, laboratories and hospitals, so a fiber optic pH sensor is proposed to measure the pH value of an aqueous solution. With the help of an acid-base indicator, an aqueous solution with different pH value has different absorption of light. Detecting the optical power of an aqueous solution, the pH value can be assessed. However, according to previous researches, the measurement range of pH value is limited just by using one acid-base indicator. The paper further proposed an improved method by using two more mixed acid-base indicators to enlarge measurement range of pH value. A mixed indicator of a methyl orange indicator and a phenol red indicator is successfully used to verify the research, while the wavelength of detecting light is 522 nm. The change in pH value is 8.22 nW / pH within pH 1~7.
50
"Numerical modelling of a Raman-Rayleigh distributed temperature fiber sensor implementing correlation techniques." Thesis, 2015. http://hdl.handle.net/10210/13831.
Full textAbstract:
M.Ing. (Electrical and Electronic Engineering)A distributed temperature fiber sensor based on the ratio of the Raman anti-Stokes to Rayleigh backscattered light components is studied. The aim of the study is to propose a method of quantifying the noise exhibited in the Rayleigh backscattered signal and further propose correlation coding techniques to reduce the noise in the Rayleigh and Raman backscattered signals. The noise in the Rayleigh backscattered signal is referred to as “interferometric noise”. When Rayleigh scattering along the length of an optical fiber occurs, some of the scattered light travels in a direction opposite to the direction of propagation, and is called backscattered light. When the coherence length of the optical source permits interactions between the Rayleigh backscattered light, there is a possibility for the interacting backscattered light, within a distance that is half the coherence length, to interfere with each other. Furthermore, when the sensing optical fiber is greater than the coherence length of the optical source, there will be several interference sections along the length of the sensing fiber causing the intensity of the Rayleigh backscattered light at the photo-detectors to vary randomly. The intensity variation gives the Rayleigh backscattered signal a jagged appearance indicating the presence of interferometric noise. The longer the coherence length of the optical sources, the larger the intensity variations in the backscattered light, that is, the more the interferometric noise exhibited. The more the interferometric noise in the Rayleigh backscattered signal, the poorer the temperature accuracy of the distributed temperature sensor based on the ratio of the Raman anti Stokes to Rayleigh backscattered components. To quantify the interferometric noise affecting the Rayleigh backscattered signal, a mathematical model based on well-known scattering and interferometry theories is developed. Using the developed mathematical noise model, noise powers of approximately -52dBm and -40dBm for coherence lengths of 4m and 24m are respectively obtained...