Dissertations / Theses on the topic 'Optical fibre gas sensor'
To see the other types of publications on this topic, follow the link: Optical fibre gas 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 fibre gas 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
Davies, Edward. "Optical fibre sensors with applications in gas and biological sensing." Thesis, Aston University, 2011. http://publications.aston.ac.uk/15800/.
Full textAbstract:
This thesis describes the study of various grating based optical fibre sensors for applications in refractive index sensing. The sensitivity of these sensors has been studied and in some cases enhanced using novel techniques. The major areas of development are as follows. The sensitivity of long period gratings (LPGs) to surrounding medium refractive index (SRI) for various periods was investigated. The most sensitive period of LPG was found to be around 160 µm and this was due to the core mode coupling to a single cladding mode but phase matching at two wavelength locations, creating two attenuation peaks, close to the waveguide dispersion turning point. Large angle tilted fibre gratings (TFGs) have similar behaviour to LPGs, in that they couple to the co-propagating cladding modes. The tilted structure of the index modulation within the core of the fibre gives rise to a polarisation dependency, differing the large angle TFG from a LPG. Since the large angle TFG couple to the cladding mode they are SRI sensitive, the sensitivity to SRI can be further increased through cladding etching using HF acid. The thinning of the cladding layer caused a reordering of the cladding modes and shifted to more SRI sensitive cladding modes as the investigation discovered. In a SRI range of 1.36 to 1.40 a sensitivity of 506.9 nm/URI was achieved for the etched large angle TFG, which is greater than the dual resonance LPG. UV inscribed LPGs were coated with sol-gel materials with high RIs. The high RI of the coating caused an increase in cladding mode effective index which in turn caused an increase in the LPG sensitivity to SRI. LPGs of various periods of LPG were coated with sol-gel TiO2 and the optimal thickness was found to vary for each period. By coating of the already highly SRI sensitive 160µm period LPG (which is a dual resonance) with a sol-gel TiO2, the SRI sensitivity was further increased with a peak value of 1458 nm/URI, which was an almost 3 fold increase compared to the uncoated LPG. LPGs were also inscribed using a femtosecond laser which produced a highly focused index change which was no uniform throughout the core of the optical fibre. The inscription technique gave rise to a large polarisation sensitivity and the ability to couple to multiple azimuthal cladding mode sets, not seen with uniform UV inscribed gratings. Through coupling of the core mode to multiple sets of cladding modes, attenuation peaks with opposite wavelength shifts for increasing SRI was observed. Through combining this opposite wavelength shifts, a SRI sensitivity was achieved greater than any single observed attenuations peak. The maximum SRI achieved was 1680 nm/URI for a femtosecond inscribed LPG of period 400 µm. Three different types of surface plasmon resonance (SPR) sensors with a multilayer metal top coating were investigated in D shape optical fibre. The sensors could be separated into two types, utilized a pre UV inscribed tilted Bragg grating and the other employed a post UV exposure to generate surface relief grating structure. This surface perturbation aided the out coupling of light from the core but also changed the sensing mechanism from SPR to localised surface plasmon resonance (LSPR). This greatly increased the SRI sensitivity, compared to the SPR sensors; with the gold coated top layer surface relief sensor producing the largest SRI sensitivity of 2111.5nm/URI was achieved. While, the platinum and silver coated top layer surface relief sensors also gave high SRI sensitivities but also the ability to produce resonances in air (not previously seen with the SPR sensors). These properties were employed in two applications. The silver and platinum surface relief devices were used as gas sensors and were shown to be capable of detecting the minute RI change of different gases. The calculated maximum sensitivities produced were 1882.1dB/URI and 1493.5nm/URI for silver and platinum, respectively. Using a DFB laser and power meter a cheap alternative approach was investigated which showed the ability of the sensors to distinguish between different gases and flow rates of those gases. The gold surface relief sensor was coated in a with a bio compound called an aptamer and it was able to detect various concentrations of a biological compound called Thrombin, ranging from 1mM to as low as 10fM. A solution of 2M NaCl was found to give the best stripping results for Thrombin from the aptamer and showed the reusability of the sensor. The association and disassociation constants were calculated to be 1.0638×106Ms-1 and 0.2482s-1, respectively, showing the high affinity of the Aptamer to thrombin. This supports existing working stating that aptamers could be alternative to enzymes for chemical detection and also helps to explain the low detection limit of the gold surface relief sensor.
2
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
3
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
4
Ibrahim, Sallehuddin. "Measurement of gas bubbles in a vertical water column using optical tomography." Thesis, Sheffield Hallam University, 2000. http://shura.shu.ac.uk/19852/.
Full textAbstract:
This thesis presents an investigation into the application of optical fibre sensors to a tomographic imaging system for use with gas/water mixtures. Several sensing techniques for measurement of two component flow using non-intrusive techniques are discussed and their relevance to tomographic applications considered. Optical systems are shown to be worthy of investigation. The interaction between a collimated beam of light and a spherical bubble is described. Modelling of different arrangements of projections of optical sensing arrays is carried out to predict the expected sensor output voltage profiles due to different flow regimes represented by four models. The four flow models investigated are: a single pixel flow, two pixels flow, half flow and full flow models. The response of the sensors is based on three models: optical path length, optical attenuation and a combination of optical attenuation model and signal conditioning. In the optical path length model, opaque solids or small bubbles, which are conveyed, may totally or partially interrupt the optical beams within the sensing volume. In the optical attenuation model, the Lambert-Beer's Law is applied to model optical attenuation due to the different optical densities of the fluids being conveyed. The combination of optical attenuation model and signal conditioning is designed to improve the visual contrast of the tomograms compared with those based on the optical attenuation model. Layergram back-projection (LYGBP) is used to reconstruct the image. A hybrid reconstruction algorithm combining knowledge of sensors reading zero flow with LYGBP is tested and shown to improve the image reconstruction. The combination of a two orthogonal and two rectilinear projections system based on optical fibres is used to obtain the concentration profiles and velocity of gas bubbles in a vertical column. The optical fibre lens is modelled to determine the relationships between fibre parameters and collimation of light into the receiver circuit. Modelling of the flow pipe is also carried out to investigate which method of mounting the fibres minimises refraction of the collimated light entering the pipe and the measurement cross-section. The preparation of the ends of the optical fibre and design of the electronics, which process the tomographic data, are described. Concentration profiles obtained from experiments on small bubbles and large bubbles flowing in a hydraulic conveyor are presented. Concentration profiles are generated using the hybrid reconstruction algorithm. The optical tomographic system is shown to be sensitive to small bubbles in water of diameter 1-10 mm and volumetric flow rates up to 1 1/min, and large bubbles in water of diameter 15-20 mm and volumetric flow rates up to 3 1/min. Velocity measurements are obtained directly from cross correlation of upstream and downstream sensors' signals as well as from upstream and downstream pixel concentration values. Suggestions for further work on optical tomographic measurements are made.
5
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
6
Shillig, Tyler. "Multi-point temperature sensing in gas turbines using fiber-based intrinsic Fabry-Perot interferometers." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/33612.
Full textAbstract:
Due to their compact size, sensitivity, and ability to be multiplexed, intrinsic Fabry-Perot interferometers (IFPIs) are excellent candidates for almost any multi-point temperature or strain application, and it is well-known that using a single-mode lead-in fiber, a multi-mode fiber section as the Fabry-Perot cavity, and an additional single-mode fiber as the tail results in a structure that generates strong interference fringes while remaining robust. Though the basic principles behind these sensors are understood, to the best of the authorâ s knowledge there hasnâ t been a thorough investigation into the design and fabrication of a chain of multiplexed IFPI sensors for industrial use in an environment where serious issues associated with the size of the test coupon, sensor placement, and mechanical reinforcement of the fiber could arise. This thesis details the preparation and results of this investigation. It turns out that fabricating a sensor chain with appropriate sensor spacing and excellent temperature response characteristics proved a significant challenge, and issues addressed include inter-sensor interference, high-temperature mechanical reinforcement for bare fiber sections, and high bending losses. After overcoming these problems, a final sensor chain was fabricated and characterized. This chain was then subjected to a battery of tests at the National Energy Technology Laboratory (NETL), where four multiplexed sensors were installed on a 2â x2â coupon in a simulated gas turbine environment. Final results are presented and analyzed. The work that went into developing this chain lays the foundation for future efforts in developing quasi-distributed temperature sensors by identifying potential obstacles and fundamental limitations for certain approaches.Master of Science
7
Allsop, Thomas David Paul. "A fibre optical strain sensor." Thesis, University of Plymouth, 1999. http://hdl.handle.net/10026.1/2779.
Full textAbstract:
Strain-sensing elements, fabricated in standard communications-grade single mode optical fibre, are increasingly being considered for application in structural health monitoring. The reason for this is the numerous advantages demonstrated by these devices compared with traditional indicators. This thesis describes work carried out on optical sensors at the University of Plymouth. The aim of this work was to achieve an optical fibre strain sensing system capable of measuring absolute strain with good resolution and having wide dynamic range, without bulky optical equipment and not susceptible to misalignment due to handling. Earlier work was devoted to study on an intrinsic Fabry-Perot interferometric sensor and an optical phase-shift detection technique. The sensing element investigated relied on the end face of an optical fibre as one mirror and the second mirror being a layer of Titanium Dioxide (TO2). Although some results are included, it was soon realised that this sensor had a number of problems, particularly with fabrication. As no simple solution presented itself, consideration was given to a sensor that made use of the change in reflectance of an intra-core fibre Bragg grating when the grating was subjected to strain. The bulk of work described in this thesis is concerned with this type of sensing element. The grating structure is inherently flexible and a number of structural formats were studied and investigated. The first and simplest grating considered was two linearly chirped Bragg gratings used in a Fabry-Perot configuration (a grating resonator). The sensor was tested using the sensing detection system and although the fabrication problems were overcome absolute strain measurement was unattainable. To achieve this end, a theoretical study of a number of grating structures was carried out using the T-matrix Formalism. Confidence in using this approach was gained by comparing the spectral behaviour of a proposed grating with results, which were given by another theoretical model for the same proposed grating. The outcome of this study was that two structures in particular showed promise with regard to absolutism (the measure of true strain) and linearity. Discussions held with the department of Applied Physics at Aston University about fabrication resulted in one of the proposed designs being abandoned due to difficulties of fabrication. The second structure showed more promise and fabrication attempts were put in hand. This grating is linearly-chirped with a Top-hat function and a sinusoidal perturbation as a taper function of the refractive index modulation. Experiments were performed, data were acquired and system performance for this sensor is presented. The thesis concludes that using such a fibre Bragg grating as the sensing element of a strain sensing system enables it to measure absolute strain without using bulky optical equipment. At present, the resolution of strain is limited by the quality of the grating being fabricated (anomalies on profile), this should improve once the fabrication technique is refined.
8
Ludden, Brendan Patrick. "A distributed optical fibre sensor." Thesis, University of Cambridge, 1997. https://www.repository.cam.ac.uk/handle/1810/272327.
Full text
9
Moss, Steven E. "Wavelength division multiplexed optical fibre sensor networks." Thesis, Manchester Metropolitan University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334635.
Full text
10
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
11
Su, Xu. "Design and Evaluation of Off-centered Core Fiber for Gas Sensing." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/99348.
Full textAbstract:
Gas Sensing Has Become a Very Important and Attractive Technique Because of Its Various Applications, Such as in the Increasingly Concerning Case of Environmental Issues, Automobile Emission Detection, Natural Gas Leakage Detection, Etc. It Also Has Significant Applications in Industries, Such as Safety and Health Monitoring in Underground Mines. Among Those Sensing Areas, Fiber-optic Sensors Have Drawn Considerable Attention Because of Its Small Size, Light Weight, High Sensitivity, and Remote Sensing Capability. However, Current Fiber-optic Gas Sensing Techniques Have Several Limitations on Their Potential for Multiplexed or Distributed Sensing Due to Difficulties Such as High Complexity or Large Loss.
To Accomplish the Goal for Multiplexed Gas Sensing, an Off-centered Core Fiber Design Is Investigated. The Eccentric Core Can Reduce Attenuation, Keep Mechanical Strength, and Lower Fabrication Cost. To Verify the Feasibility of the Design, Fiber Field Distribution Is First Studied in Simulation, Which Will Be Discussed in Detail in Chapter 2. Then Two Fiber Samples with a Length of 10 Cm and 40 Cm Are Prepared and Placed in a Custom Methane Sensing System for Gas Absorption Testing, Which Is Detailed in Chapter 3. From Etching Analysis, Localized Surface Defects Are Found as the Main Reason for Power Loss. Performance Such as Detection Resolution and Sensitivity Are Investigated. In Chapter 4, Theoretical Evaluations Have Been Conducted for Multiplexed Sensors Performances Using the Off-centered Core Fiber to Study the Impact Fiber Parameters on Sensing System Design. The Conclusion and Summary Are Presented in Chapter 5.Master of Science
Gas Sensing Has Become a Very Important and Attractive Technique Because of Its Various Applications, Such as in the Increasingly Concerning Case of Environmental Issues, Automobile Emission Detection, Natural Gas Leakage Detection, Etc. It Also Has Significant Applications in Industries, Such as Safety and Health Monitoring in Underground Mines. Among Those Sensing Areas, Fiber-optic Sensors Have Drawn Considerable Attention Because of Its Small Size, Light Weight, High Sensitivity, and Remote Sensing Capability. However, Current Fiber-optic Gas Sensing Techniques Have Several Limitations on Their Potential for Long Distance Distributed Sensing Due to Difficulties Such as High Fabrication Complexity. In This Work, a Fiber-optic Gas Sensor with Special Structure Was Designed. The Sensor Can Reduce Attenuation, Keep Mechanical Strength, and Lower Fabrication Cost. To Verify the Feasibility of the Design, Theory Analysis and Simulation Were Conducted, Which Will Be Discussed in Detail in Chapter 2. Then Two Samples with a Length of 10 Cm and 40 Cm Were Prepared and Placed in a Custom Methane Sensing System for Testing. And Their Performance Such as Sensitivity Is Investigated. In Chapter 4, Theoretical Evaluations Have Been Conducted for Multiplexed Sensors Performances Evaluation to Study the Impact Fiber Parameters on Sensing System Design. The Conclusion and Summary Are Presented in Chapter 5.
12
Laufer, Jan. "Photothermal determination of optical coefficients using an optical fibre sensor." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.394370.
Full text
13
Merchant, David Frank. "Optical fibre fluorimeter for online measurement." Thesis, Liverpool John Moores University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313161.
Full text
14
Wang, Dong Ning. "White light interferometric sensor systems." Thesis, City University London, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283188.
Full text
15
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.
16
Murtaza, Ghulam. "Dual wavelength referenced intensity modulated optical fibre sensor system." Thesis, Manchester Metropolitan University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358834.
Full text
17
Glomon, Lhusak. "Source based chromatic methodology for optical fibre sensor systems." Thesis, University of Liverpool, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400231.
Full text
18
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
19
Wong, Yuen Mei. "Optimising the plastic optical fibre evanescent field biofilm sensor." Thesis, Liverpool John Moores University, 2008. http://researchonline.ljmu.ac.uk/5906/.
Full textAbstract:
This thesis describes the development, characterisation and application of large diameter multimode plastic optical fibre (POF) sensors using evanescent field modulation. The exposed polymethylmethacrylate (PMMA) core of the POF fibre forms the sensor interface that detects refractive index changes of a measurand acting as the cladding. When a liquid measurand is used, the sensor can detect changes in refractive index, absorption and suspended particulates. It is this simple mechanism by which the evanescent field POF sensor operates. The evanescent field POF sensor has been characterised for refractive index of surrounding liquid from 1.33 to 1.49. The sensor demonstrated accuracy of ± 7x 10-3 refractive index units below 1.4 and ±2x 10-3 refractive index units above 1.4. Components have been selected and designed for this project to ruggedise the sensor, to make the sensor more self-contained and cheaper. The original design of the test conditions did not allow for optimum deployment of the sensor as it stripped out the very modes of light that were required for sensing purposes. The system was also operating under pressure, not reflecting the real conditions under which the sensor would be operating. The re-design of test conditions holds the sensor without straining the POF and operates under normal atmospheric pressure. The POF sensor was demonstrated reacting to a real measurand eg biofilm in which initial growth affects the optical properties at the core cladding interface by refractive index modulation. This sensor was capable of measuring biofouling and scaling at water interfaces. The sensor was trialled in a European Commission funded project (CLOOPT) to study biofouling and scaling in closed loop water systems such as heat exchangers in the cooling tower of an electric power plant, and as an interface sensor for water quality monitoring (AQUA-STEW) involving biofilm removal and surface cleansing with a new application for contact lens protein removal systems. Tapering multimode POF was a desirable goal as this increases the proportion of light coupled into the core available for sensing purposes, to achieve a more sensitive evanescent field POF sensor. Optically clear and consistent smooth tapering of ends and mid-lengths of POF fibre were achieved through chemical removal of material. The tapered POF sensor was characterised with a range of refractive indices, and it exhibited two distinct regions; the water/alcohol region below 1.4 refractive index units, and the oil region above 1.4 suggesting the sensor's use as an oil-in-water, or water-in-oil sensor. From 95% confidence limits, the accuracy of the POF was ±O.006 refractive index units (to 2 standard deviations) for fluids of refractive indices above 1.4. Tapered POF is sensitive to refractive index providing a cheap, easy to handle and rugged throwaway sensor for water and beverage process and quality monitoring.
20
Abokhamis, Mousavi Seyed Mohammad. "Exploring optical nonlinearity in gas-filled hollow core fibre." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/428037/.
Full textAbstract:
The growing need for novel light sources in variety applications increases the demand for laser sources operating in many different range of spectrum. Despite the success in development of mid-infrared (mid-IR) lasers, which are essential in many applications such as: environmental science, bio-science and physics, there are still lack of reliable lasers in this range with existing fibre laser technology compatibility. Meanwhile the nonlinearity in gases has been explored extensively from the very beginning of nonlinear optics, however, new developments in pulsed lasers and fibre design provide opportunities for more applications. The introduction of Hollow Core Photonic Crystal Fibres (HC-PCF) has revolutionised the area of nonlinearity in gaseous media by offering a single-mode confined light beam for very long distances. In this thesis, the focus was on mid-IR pulse generation by Raman frequency conversion in a gas-filled HC-PCF. Due to reliable performance and compatibility of fibre lasers with HC-PCFs, and towards fully fiberized source, an erbium-doped fibre laser (1.55 μm) has been selected as the pump for this project. In order to reach as far as possible into the mid-IR region, hydrogen has been selected as the filling gas of fibre, due to its large frequency shift and high Raman gain. The large frequency shift and mid-IR operating range required a new fibre design with a broadband transmission window and relatively low loss in mid-IR. After studying conventional HC-PCF structures, the recently proposed Nested Anti-resonant Nodeless Fibre (NANF) has been selected as the most suitable option for the purpose of this thesis [71]. Two NANFs, made of silica and tellurite, have been designed and optimized through the use of the developed Finite Element Method (FEM) toolbox in this thesis for operating wavelengths at pump (1.55 μm) and 1st Stokes (4.35 μm). A novel design has also been introduced in NANFs which shows polarization maintaining feature as good as the latest state-of-the-art HC-PBGF type [77]. The proposed design also shows polarizing capability in addition to its polarization maintaining by presenting a large loss ratio (~30 dB) between different polarizations of propagating light through it. The pulse propagation throughout the hydrogen-filled NANFs has been investigated by modelling the Raman response of hydrogen and numerically solving the Generalized Nonlinear Schrödinger Equation (GNLSE). Simulations show promising results for frequency conversion towards mid-IR and the possibility of Raman lasers in this region by considering different gas and using the readily available air in HC fibres. Furthermore, in this work, the nonlinear dynamics of atmospheric air-filled HC fibres have been studied, ranging from Raman down conversion process to a high spectral power density supercontinuum spanning from 850 to 1600 nm. A semi-quantum model for air has been adopted and integrated into the GNLSE, which surpasses the limitations of simple model. Using the adopted model, the experimental results have been reproduced without any extra computational cost. A rigorous study has been performed on nonlinear dynamics of pulse propagation in air-filled HC fibres and the origin of many nonlinear phenomenon are identified.
21
Love, Adrian. "Hollow core optical fibre based gas discharge laser systems." Thesis, University of Bath, 2018. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760983.
Full textAbstract:
The humble electrically pumped gas laser has undergone little development in its fifty year life span due to the lack of an effective method to confine light within a hollow waveguide of any appreciable length in which an electrical discharge could be contained. New technologies in the field of anti-resonant guiding hollow core fibres present an opportunity to re-invent the gas laser. A recent breakthrough in the field demonstrated that DC pumped glow discharges of a helium and xenon gas mixture could not only be sustained in such a fibre, but also exhibited signs of gain on a number of mid-IR neutral xenon laser lines. The research presented in this thesis is a continuation of that project. The system was redesigned to incorporate two mirrors so that a cavity could be constructed. The previously hinted at gain on the 3:51 μm xenon line was confirmed through a series of CW measurements of the cavity, as was a polarisation of the laser due to a polarisation dependent output coupler. Further observation of the discharges revealed that they were of a pulsed nature, and that the mid-IR laser light was present in the discharge afterglow. A response to the cavity mirrors was observed in this afterglow pulse on the 3:11 and 3:36 μm xenon lines in addition to the 3:51 μm line previously seen. Through fast detection a modulation of the output power due to cavity mode beating effects was detected. The high gain and narrow bandwidth of the xenon laser lines resulted in a frequency pulling effect, and the mode separation in the 'hot' laser cavity was measured to be lower than in the 'cold' cavity. It was observed through pressure optimisation experiments in helium-xenon that higher output powers could be achieved by using lower partial pressures of xenon. This was exploited with neon-xenon mixtures, where the lower ionisation potential of neon allowed a lower pressure of xenon. Discharges were also achieved in helium-neon and argon gas mixtures.
22
Hu, Yiqun. "Digital Spatial Domain Multiplexing technique for optical fibre sensor arrays." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245041.
Full text
23
Zhang, Feng Hong. "A novel optical fibre sensor based on inter-fibre distributed coupling for particle concentration measurement." Thesis, Liverpool John Moores University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361510.
Full text
24
Dowker, Kenneth Paul. "Long period fibre grating as gas sensor for environmental pollution monitoring." Thesis, Sheffield Hallam University, 2003. http://shura.shu.ac.uk/19578/.
Full textAbstract:
The principle objective of the work presented in this thesis is to investigate and demonstrate the possibility of utilising the inherent properties of long-period gratings (LPGs) to detect the existence and concentration of a given gas in the region immediately surrounding the fibre cladding. The principle and the viability of using LPGs for sensor applications is supported by the preliminary results reported here. However, the sensitivity of the sensor requires further improvement before it can in any way challenge the existing sensors in this field. The operational characteristics and limitations of existing optical sensors are reviewed and the advantages of a LPG based optical sensor highlighted. Thorough explanations of the theory and principles of light propagation, mode formation, and mode coupling in optical fibres are presented. Computer simulations predicting the optical effects due to changes in ambient indices from theoretical conditions are successfully derived, confirming the results obtained by experimental investigation. Various established coating methods are investigated and utilised in the application of optically sensitive compounds adsorbed onto the cladding with different levels of success, the poly-electrolyte self assembly (PESA) and evaporation methods proving most suitable. A novel method of monitoring the build up of PESA layers in-situ using surface plasmon resonance (SPR) methods is introduced. The coating chemicals used in this investigation showed some optical sensitivity at the optimum wavelengths used in optical fibres to the various gases being monitored, in most cases causing a detectable change in the optical characteristics of the modes in the LPG.This study has shown the possibility of using a suitably prepared LPG as a gas sensor. The LPG is coated with a chemical whose refractive index is changed by absorption of a given gas and thus the change in the coupling wavelengths being caused by the existence of the gas. Maximum shifts in coupling wavelength of +/-1.5 nm for relatively high gas concentrations are observed. The possibility of using a coating material which absorbs water, or surrounding the LPG with a suitable liquid is also demonstrated, the refractive index of the coating or liquid and thus the coupling wavelength shift being affected by the reaction of the gas. The possibility of using a single temperature immune LPG for ambient index sensing by observing different coupling wavelengths in the same grating is also reported.
25
Wang, Qi. "Studies of multimode fibre linked white light interferometric sensor systems." Thesis, City University London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389649.
Full text
26
Shen, Yonghang. "Characterization of optical fibre sensor systems for applications at high temperatures." Thesis, City University London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.421643.
Full text
27
Radi, Haidar M. "Frequency hopping spread spectrum multiplexing for interferometric optical fibre sensor networks." Thesis, Manchester Metropolitan University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387483.
Full text
28
Masoudi, Ali. "Design and application of a distributed optical fibre dynamic strain sensor." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/375125/.
Full textAbstract:
Over the past two decades, distributed optical fibre sensors (DOFS) based on Brillouin and Raman scattering have been extensively studied. As a result, a wide range of distributed temperature and strain sensors with different sensing range and accuracy levels have been developed. However, due to the weak nature of Brillouin and Raman scattering, most of the research in this field has been focused on DC or quasi-DC measurement of temperature and strain. On the other hand, the Rayleigh-based DOFS which have been previously proposed are only able to detect dynamic disturbances along the sensing fibre. In this thesis, a new sensing technique has been developed which is capable of quantifying and tracking multiple dynamic perturbations along the sensing fibre, simultaneously. The sensing mechanism of the proposed technique relies on the phase of the Rayleigh backscattered light. For any given segment along the fibre, the difference in the phase of the backscattered light radiating from the two ends of that segment changes as a function of the external perturbations at that segment. Therefore, dynamic vibration along the sensing fibre can be extracted by comparing the phase of the backscattered light from two different sections of the sensing fibre. By implementing this technique using an imbalanced Mach-Zehnder Interferometer (IMZI), a distributed sensor was developed that was capable of quantifying dynamic perturbations within the frequency range of 200Hz ~5kHz along a 1km sensing fibre. Furthermore, the same principle was used to develop a distributed magnetic field sensor. By coupling an optical fibre to a magnetostrictive wire and by using this combination as a magnetic field to strain transducer, a distributed magnetic field sensor was formed with magnetic intensity range of 1Gs~ 8Gs and frequency range of 50Hz ~5kHz. In addition, the IMZI arrangement was used as a frequency-to-intensity convertor to develop a distributed dynamic strain sensor based on Brillouin scattering. The proposed sensor exhibited a strain range of 400µέ 4mέ and a sensing range of 2km.
29
Liu, Chen. "Advanced optical fibre grating sensors for biochemical applications." Thesis, Bangor University, 2019. https://research.bangor.ac.uk/portal/en/theses/advanced-optical-fibre-grating-sensors-for-biochemical-applications(29757d94-bfe1-4d75-a4db-8563be1a056f).html.
Full textAbstract:
This thesis describes a detailed study of advanced fibre optic sensors and their applications for label-free biochemical detection. The major contributions presented in this thesis are summarised below. A self-assembly based in-situ layer-by-layer (i-LbL) or multilayer deposition technique has been developed to deposit the 2D material nanosheets on cylindrical fibre devices. This deposition technique is based on the chemical bonding associated with the physical adsorption, securing high-quality 2D materials coating on specific fibre cylindrical surface with strong adhesion as well as a prospective thickness control. Then a " Photonic-nano-bio configuration", which is bioprobes immobilised 2D-(nano)material deposited fibre grating, was built. 2D material overlay provides a remarkable analytical platform for bio-affinity binding interface due to its exceptional optical and biochemical properties. EDC (1-ethyl-3-(3-dimethylaminopropyl)carbodiimide) and NHS (NHydroxysuccinimide) were used to immobilise bioprobes. This kind of configuration is considered to have many advantages such as: enhanced RI sensitivity, enrich immobilisation sites, improved binding efficiency, selective detection. Followed by this configuration, several label-free biosensors were developed. For example, graphene oxide coated dual-peak long period grating (GO-dLPG) based immunosensor has been implemented for ultrasensitive detection of antibody/antigen interaction. The GO-LPG based biosensor has been developed for label-free haemoglobin detection. Apart from biosensors, the black phosphorus (BP) integrated tilted fibre grating (TFG) has been proposed, for the first time, as BP-fibre optic chemical sensor for heavy metal (Pb2+ ions) detection, demonstrating ultrahigh sensitivity, lower limit of detection and wider concentration range. Ultrafast laser micromachining technology has been employed to fabricate long period grating (LPG) and microstructures on optical fibre. The ultrafast laser micromachined polymer optical fibre Bragg grating (POFBG) has been developed for humidity sensing, showing the significant improvement with the reduced response time.
30
Azim-Araghi, Mohammad Esmaeil. "Electrical, optical and gas sensor properties of chloroaluminium (ClAlPc)." Thesis, Lancaster University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387649.
Full text
31
Lewin, A. C. "An investigation of optical fibre interferometric vibration and rotation measurement techniques." Thesis, University of Kent, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383750.
Full text
32
Fouchal, Farid. "Composite cure assessment using spectral analysis (via an embedded optical fibre sensor)." Thesis, De Montfort University, 2001. http://hdl.handle.net/2086/4302.
Full text
33
Marshall, Raymond Hugh. "A study of optical-fibre electronically-scanned white light interferometric sensor systems." Thesis, City University London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266372.
Full text
34
Cheevers, Kevin. "Optical Fibre-Based Hydrophone and Critical Ignition in Detonation Cells." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42793.
Full textAbstract:
This thesis is composed of two distinct parts. The first part of this work addresses the problem of critical ignition behind a decaying shock wave in the context of cellular detonations. Low-pressure (4.1 kPa) shock tube experiments were performed in a thin rectangular channel using the highly-unstable mixture of CH4 + 2O2 and the weakly-unstable mixture of 2H2 + O2 + 7Ar, with Schlieren visualization of the flow field. The dynamics of the lead shock in a detonation cell was reconstructed from measurements of the lead shock position and curvature. The post-shock state and the expansion rate along the path of a Lagrangian particle crossing the lead shock at any given point in the cell cycle were evaluated with the shock jump and shock change equations. The chemical evolution behind the shock was then integrated using a detailed chemistry model. Quenching of the post-shock reaction zone was found within the first half of the detonation cell for both mixtures, with quenching occurring earlier in the highly unstable mixture. Simplified models derived from 1-step and 2-step chemistry models very accurately predict the quenching of the post-shock reactions and the evolution of the ignition delay through the cell.
The second part describes the assembly and characterization of a fibre-optic probe hydrophone (FOPH) for the measurement of shock waves associated with blast-induced neuro-trauma. Compared to traditional polyvinylidene difluoride (PVDF) hydrophones, the assembled FOPH has a higher bandwidth and smaller active diameter, which are comparable to the characteristic time and thickness of shock waves associated with blast-induced neuro-trauma. However, the sensitivity of FOPHs are substantially lower than traditional hydrophones. We assemble a FOPH and provide detailed calculations and measurements of its sensitivity (0.66 mV/MPa) , noise floor, and spatial resolution. The 150 MHz bandwidth, limited by the photodetector, is sufficient for resolving shock waves with over-pressures of up to 174 kPa with 3 measurement points. Experimental measurements of the system noise gives a floor of 260 Pa/√Hz . A detailed noise analysis finds that the system is limited by photodetector noise (215 Pa/√Hz), which is 4x the fundamental shot noise limit, closely followed by a laser noise of 150 Pa/√Hz. We conclude that the system noise floor is insufficient for resolved measurements of the post-shock pressure in the range associated with blast-induced neuro-trauma. From our noise analysis, we quantify the sensitivity enhancement required for resolving this regime, and we conclude that sensitivity-enhancing fibre-coatings could provide a sufficient increase in sensitivity.
35
Bashour, Rami. "High voltage optical fibre sensor for use in wire relay electrical protection systems." Thesis, University of Derby, 2016. http://hdl.handle.net/10545/621343.
Full textAbstract:
The last few decades have a wide spread use of optical fibre sensors in many applications. Optical fibre sensors have significant benefits over existing conventional sensors such as; high immunity to electromagnetic interference, the ability to transmit signal over long distance at high bandwidth, high resolution, usage in hazardous environments and no need for isolation when working at high voltages. The measurement of high voltages is essential for electrical power systems as it is used as a source of electrical information for Relay Protection Systems (RPS) and load management systems. Electrical Power Systems need to be protected from faults. Faults can range from short circuits, voltage dips, surges, transients etc. The Optical High Voltage sensor developed is based on the principle that the Lead Zirconate Titanate (PZT) electrostriction displacement changes when a voltage is applied to it. The displacement causes the fibre (FBG) which is bonded to the PZT material to have a resultant change in the wavelength. An optical fibre sensor prototype has been developed and evaluated that measures up to 250 V DC. Simulation using ANSYS software has been used to demonstrate the operational capability of the sensor up to 300kV AC. This sensor overcomes some of the challenges of conventional sensors issues like electromagnetic interference, signal transmission, resolution etc. R BASHOUR 2 A novel optical fibre high voltage based on the Kerr effect has been demonstrated. The The Kerr effect was determined using Optsim (R-Soft) software and Maxwell software was used to model an optical Kerr Cell. Maxwell software is an electromagnetic/electric field software used for simulating, analysing, designing 2D and 3D electromagnetic materials and devices. It uses highly accurate Finite Element techniques to solve time varying, static, frequency domain electric and electromagnetic fields. A Relay Protection System on electrical networks was discussed in detail. Keywords: Fibre Bragg Grating, Fibre Optics Sensors, Piezoelectricity, Kerr effect, Relay Protection Systems.
36
Zeakes, Jason S. "Extrinsic Fabry-Perot Interferometric hydrogen gas sensor." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06162009-063525/.
Full text
37
Cusworth, S. D. "An extrinsic optical fibre sensor system for the measurement of pressure and temperature." Thesis, Manchester Metropolitan University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370938.
Full text
38
Hayes, Simon Antony. "Development of a reinforcing fibre light-guide for use as a damage sensor within composite structures." Thesis, Brunel University, 1995. http://bura.brunel.ac.uk/handle/2438/7119.
Full textAbstract:
This study presents the results of an investigation to develop a novel sensor which would give a direct indication of the extent of impact damage in a composite. This was achieved by using glass reinforcing fibres to produce a light-guide, which was embedded within a composite laminate. The laminate was then subjected to impact events or bending stresses of sufficient magnitude to cause damage. The impact energies used in this study varied between 2 and 10 Joules, and the indentation depths varied between 0.125 and 1 mm, allowing damage propagation to be monitored. The fall-off in the transmitted light was used to monitor the level of damage, along with C-scanning and sectioning to provide reference data. The use of reinforcing fibres to produce the sensor meant that the strains required to cause failure in the fibres was realistically close to those of the composite constituents. Changes in the transmission characteristics of the sensor were found to correspond to real failure events occurring during impact.
39
Zheng, Gang. "Development of advanced birefringent fibre force sensor systems based on frequency modulation continuous wave (FMCW) technology." Thesis, Glasgow Caledonian University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337411.
Full text
40
Zhang, Jian. "Zeolite Thin Film-Fiber Integrated Optical Sensors for Highly Sensitive Detection of Chemicals in Gas and Liquid Phases." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1195680520.
Full text
41
DonlagicÌ, Denis. "Microbend sensor structure based on selective excitation and filtering of the modes in graded index optical fibres." Thesis, University of Strathclyde, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248635.
Full text
42
Tu, Minh Hieu. "Investigation of metal nanomaterials as a sensing element in LSPR-based optical fibre sensor development." Thesis, City University London, 2014. http://openaccess.city.ac.uk/5919/.
Full textAbstract:
This thesis aims to explore and demonstrate the potential of using optical fibres both as a waveguide material and a transducer for wide sensing applications, based on a comprehensive review of the localised surface plasmon resonance (LSPR) phenomenon, which occurs at a nanoscale level when light interacts with metallic nanoparticles at a resonance wavelength. The LSPR effect of metallic nanomaterials has shown a strong dependence on the local surrounding environment. A small change for example in the refractive index or in the solution concentration can result in a variation in the LSPR spectrum. Based on this underpinning sensing mechanism, a portable system using an optical fibre coated with gold nanoparticles (AuNPs) as a sensing probe has been developed and tested for the refractive index measurement. Coupled with this, a systematic approach has been developed and applied in this work to optimize the performance of the developed system by considering several key factors, such as the size of nanoparticles produced, pH, coating time and coating temperature. The above optimised probes coated with gold-nanoparticles are further cross-compared with those optimized but coated with gold nanorods with a high aspect ratio. Both types of probes are also prepared for a specific biosensing application based on the antibody-antigen interaction to create wavelength-based sensors for the detection of anti-human IgG. Both probes have exhibited excellent refractive index (RI) sensitivity, showing ~914 nm/RIU (refractive index unit) for the probe coated with gold nanoparticles and ~601 nm/RIU for the one coated with gold nanorods. When using the modified probes for the detection of anti-human IgG, both probes are able to achieve a good LOD (limit of detection) at 1.6 nM. Based on the above cross-comparison, further research has been undertaken to explore the potential of nanoparticles of the alloy of gold and silver, with an aim to combine the robustness of gold and the excellent LSPR effect of silver. To do so, various alloy particles with varied gold/silver ratio and sizes have been prepared and tested for their respective refractive index sensitivities. The probe coated with alloy particles with bigger size and higher silver content has shown better performance in RI sensing. The work has shown a clear relationship between the size of alloys, the content ratio of alloys and RI sensitivity. Research has also been undertaken in this thesis to explore the excellent LSPR effect of hollow nanoparticles resulting from the enhanced coupling between the interior and exterior of the hollow particles. Gold hollow nanocages have been successfully synthesised and tested with different hollowness and a LSPR sensor coated with gold nanocages has shown an excellent sensitivity as high as ~1933 nm/RIU, which is more than 3 times higher than that coated with AuNPs. This result has confirmed that a significant improvement in sensitivity can be made possible for further biosensing as well as chemical sensing applications.
43
Azzi, Victor, and Victor Azzi. ""Sensor-in-fibre" optical probes for molecular sensing in the gastrointestinal tract of murine models." Master's thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/37631.
Full textAbstract:
L’obésité et les maladies cardiométaboliques sont des problèmes de santé publique dans les populations nordiques du Canada ainsi qu’à travers le monde. Il est actuellement proposé que l’augmentation de ces désordres est en partie causée par divers facteurs environnementaux qui génèrent des changements importants du microbiote intestinal. Cette communauté microbienne qui peuple notre tractus gastrointestinal joue un rôle clé dans le métabolisme de nutriments, mais peut aussi avoir des effets néfastes lorsque son équilibre avec l’hôte est perturbé. Cette compréhension a mis en évidence le manque d’outils prédictifs permettant un diagnostic rapide et efficace dans le domaine biomédical. L’analyse actuelle du microbiote est réalisée à posteriori au niveau des selles, ce qui requiert du personnel hautement qualifié de même que des procédures longues et dispendieuses. L’objectif de ce projet est de concevoir un capteur optique qui, une fois implanté dans l’intestin, permettra de détecter en temps réel des biomarqueurs clés produit par le microbiome intestinal. Dans le cadre d’une preuve de concept, une architecture fibrée simple permettant de mesurer quantitativement des variations de pH est démontrée. Contrairement aux capteurs fibrés traditionnels, la sonde optique de ce projet exploite l’onde évanescente générée sur la périphérie de l’interface pour exciter des nanomatériaux greffés dont les propriétés de fluorescence varient selon leur environnement chimique. Les mesures sont possibles grâce à un système optique mobile contrôlé par un logiciel convivial qui permet à un utilisateur nonexpert d’utiliser l’appareil. Les résultats confirment qu’avec un étalonnage préalable il est possible avec cette sonde modèle de prendre des mesures quantitatives du pH en temps réel in vitro. Les expériences préliminaires suggèrent que la sonde permet aussi de mesurer le pH en temps réel dans l’intestin in vivo.L’obésité et les maladies cardiométaboliques sont des problèmes de santé publique dans les populations nordiques du Canada ainsi qu’à travers le monde. Il est actuellement proposé que l’augmentation de ces désordres est en partie causée par divers facteurs environnementaux qui génèrent des changements importants du microbiote intestinal. Cette communauté microbienne qui peuple notre tractus gastrointestinal joue un rôle clé dans le métabolisme de nutriments, mais peut aussi avoir des effets néfastes lorsque son équilibre avec l’hôte est perturbé. Cette compréhension a mis en évidence le manque d’outils prédictifs permettant un diagnostic rapide et efficace dans le domaine biomédical. L’analyse actuelle du microbiote est réalisée à posteriori au niveau des selles, ce qui requiert du personnel hautement qualifié de même que des procédures longues et dispendieuses. L’objectif de ce projet est de concevoir un capteur optique qui, une fois implanté dans l’intestin, permettra de détecter en temps réel des biomarqueurs clés produit par le microbiome intestinal. Dans le cadre d’une preuve de concept, une architecture fibrée simple permettant de mesurer quantitativement des variations de pH est démontrée. Contrairement aux capteurs fibrés traditionnels, la sonde optique de ce projet exploite l’onde évanescente générée sur la périphérie de l’interface pour exciter des nanomatériaux greffés dont les propriétés de fluorescence varient selon leur environnement chimique. Les mesures sont possibles grâce à un système optique mobile contrôlé par un logiciel convivial qui permet à un utilisateur nonexpert d’utiliser l’appareil. Les résultats confirment qu’avec un étalonnage préalable il est possible avec cette sonde modèle de prendre des mesures quantitatives du pH en temps réel in vitro. Les expériences préliminaires suggèrent que la sonde permet aussi de mesurer le pH en temps réel dans l’intestin in vivo.
Obesity and cardiometabolic diseases (CMD) are major public health issues among Canada’s northern population and throughout the world. It is believed that the exponential rise in CMD incidence is due to numerous environmental factors, which are driving important changes in the gut microbiome. This microbial community which populates our intestinal tract plays a key role in nutrient and energy metabolism, but can also drive pathogenic mechanisms when its interaction with the host is disrupted. This understanding has highlighted the lack of predictive tools and biomarkers for rapid and efficient diagnostic of various diseases within the medical field. Current analysis of the gut microbiota is mostly based on sequencing technologies to determine microbial composition and gene expression, while functional analyses are limited to surrogate markers of microbial activities through stool metabolites. The goal of this study is to develop a “Sensor-in-Fibre” probe with the capacity to detect key microbiome-derived molecules relevant to CMD pathogenesis in real time in vivo. The optical probe takes advantage of evanescent fields generated on its peripheral interface to excite species-selective surface-grafted sensing nanomaterials that have varying fluorescent properties based on the target molecules present in the surrounding environment. As a model system, FITC functionalized with (3-aminopropyl)triethoxysilane was grafted on the periphery of an optical fiber, leading to qualitative pH measurements revealed through fluorescence emission qualities. These measurements are possible due to the use of a mobile signal collection apparatus in conjunction with custom software made to enable a non-expert technician to use it. The experimental results demonstrate that, with the appropriate preparation, it is possible to quantitatively measure pH with this probe structure in vitro and preliminary studies suggest that the probe is also capable of measuring pH in vivo in real time.
Obesity and cardiometabolic diseases (CMD) are major public health issues among Canada’s northern population and throughout the world. It is believed that the exponential rise in CMD incidence is due to numerous environmental factors, which are driving important changes in the gut microbiome. This microbial community which populates our intestinal tract plays a key role in nutrient and energy metabolism, but can also drive pathogenic mechanisms when its interaction with the host is disrupted. This understanding has highlighted the lack of predictive tools and biomarkers for rapid and efficient diagnostic of various diseases within the medical field. Current analysis of the gut microbiota is mostly based on sequencing technologies to determine microbial composition and gene expression, while functional analyses are limited to surrogate markers of microbial activities through stool metabolites. The goal of this study is to develop a “Sensor-in-Fibre” probe with the capacity to detect key microbiome-derived molecules relevant to CMD pathogenesis in real time in vivo. The optical probe takes advantage of evanescent fields generated on its peripheral interface to excite species-selective surface-grafted sensing nanomaterials that have varying fluorescent properties based on the target molecules present in the surrounding environment. As a model system, FITC functionalized with (3-aminopropyl)triethoxysilane was grafted on the periphery of an optical fiber, leading to qualitative pH measurements revealed through fluorescence emission qualities. These measurements are possible due to the use of a mobile signal collection apparatus in conjunction with custom software made to enable a non-expert technician to use it. The experimental results demonstrate that, with the appropriate preparation, it is possible to quantitatively measure pH with this probe structure in vitro and preliminary studies suggest that the probe is also capable of measuring pH in vivo in real time.
Résumé en espagnol
Résumé en espagnol
44
Antelius, Mikael. "Wafer-scale Vacuum and Liquid Packaging Concepts for an Optical Thin-film Gas Sensor." Doctoral thesis, KTH, Mikro- och nanosystemteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-119839.
Full textAbstract:
This thesis treats the development of packaging and integration methods for the cost-efficient encapsulation and packaging of microelectromechanical (MEMS) devices. The packaging of MEMS devices is often more costly than the device itself, partly because the packaging can be crucial for the performance of the device. For devices which contain liquids or needs to be enclosed in a vacuum, the packaging can account for up to 80% of the total cost of the device. The first part of this thesis presents the integration scheme for an optical dye thin film NO2-gas sensor, designed using cost-efficient implementations of wafer-scale methods. This work includes design and fabrication of photonic subcomponents in addition to the main effort of integration and packaging of the dye-film. A specific proof of concept target was for NO2 monitoring in a car tunnel. The second part of this thesis deals with the wafer-scale packaging methods developed for the sensing device. The developed packaging method, based on low-temperature plastic deformation of gold sealing structures, is further demonstrated as a generic method for other hermetic liquid and vacuum packaging applications. In the developed packaging methods, the mechanically squeezed gold sealing material is both electroplated microstruc- tures and wire bonded stud bumps. The electroplated rings act like a more hermetic version of rubber sealing rings while compressed in conjunction with a cavity forming wafer bonding process. The stud bump sealing processes is on the other hand applied on completed cavities with narrow access ports, to seal either a vacuum or liquid inside the cavities at room temperature. Additionally, the resulting hermeticity of primarily the vacuum sealing methods is thoroughly investigated. Two of the sealing methods presented require permanent mechanical fixation in order to complete the packaging process. Two solutions to this problem are presented in this thesis. First, a more traditional wafer bonding method using tin-soldering is demonstrated. Second, a novel full-wafer epoxy underfill-process using a microfluidic distribution network is demonstrated using a room temperature process.QC 20130325
45
Sargeant, Ramon Bradley. "A multi-axial optical fibre and linear polarizer based force and torque sensor for dexterous robotic fingertips." Thesis, King's College London (University of London), 2014. http://kclpure.kcl.ac.uk/portal/en/theses/a-multiaxial-optical-fibre-and-linear-polarizer-based-force-and-torque-sensor-for-dexterous-robotic-fingertips(a9c419a3-901e-4a56-9b02-00648539d17e).html.
Full textAbstract:
As robots play a more pervasive role in our everyday activities more and more research emphasis is being placed on having robots interact directly with humans, whether in terms of taking care of the elderly, medical interventions or performing dangerous or hazardous tasks. Another trend is for robots to use existing human tools to perform desired actions since it is also not always possible or cost effective to design special tools for every robot. This trend has led to the development of anthropomorphic dexterous manipulators that can perform equally or better than the human hand. Thus the accelerating trend is not only to design a dexterous manipulator but to focus on its ability to grasp and manipulate different and sometimes unknown objects. One of the most researched types of grasp is the precision grasp which accounts for over 80 % of the grasps performed by humans on a daily basis. Precision grasps are grasps involving the fingertips and are generally used for tasks that require fine manipulation skills. Fingertip sensors are therefore important for dexterous manipulators since humans can identify salient properties of an object and formulate effective manipulation strategies solely by grasping the object. This PhD project focuses on developing fingertip sensors, specifically force and torque fingertip sensors that can be integrated into the fingertip of an existing dexterous manipulator and gather contact force and torque information during a grasping event. Another goal is to make the sensor magnetic resonant (MR) compatible so that it can be used in high magnetic environments, as in the case of medical, magnetic resonance imagining applications. To accomplish these goals two sensors were developed based on light intensity modulation and novel sensing structures. Optical sensing schemes were chosen because they are not susceptible to magnetic interference, the sensor and its light source can be separated by long distances without significant signal attenuation and the size and weight of the actual sensing element can be reduced since the processing electronics can be positioned far from the sensing structure. The first sensor developed, as part of this PhD work, was a 2-DOF sensor which used a combination of axially-aligned fibres and linear polarizers to modulate the light to measure the applied force and torque respectively. The use of linear polarizers as the main sensing technique for force and torque sensing is a new area of research since linear polarizers have a defined response curve and can be easily cut into any desired shape and size. The experiments conducted with the 2-DOF sensor showed that the linear polarizer response was superior to traditional axially-aligned and reflective techniques and it was tolerant of small deviations and twists in the sensing structure. The second sensor improved on the first sensor by increasing the number of degrees of freedom from two to six by using a parallel-type 3-UPS (Universal Prismatic Spherical) sensing structure to allow measuring six degrees of movement. All of the joints of the sensing structure were made of nitinol flexures to reduce friction and all of the links were made of plastic and bonded together to produce a flexible but light and strong structure. Another improvement was that all of the optical modulation sensors on the sensing structure were based on linear polarizers thereby reducing the possibility of misalignment errors caused by the transmitting and receiving fibres moving out of axial alignment. The new sensor therefore satisfies the design requirements and the experiments conducted showed that Light Intensity Modulation (LIM) using linear polarizers and an appropriate sensing structure can produce an accurate and versatile force and torque sensor.
46
Lakkis, Sari. "New Gas Sensor for Exhaust Emissions of Internal Combustion Engines." Thesis, Versailles-St Quentin en Yvelines, 2014. http://www.theses.fr/2014VERS0064/document.
Full textAbstract:
L’analyse des gaz d’échappement des moteurs à combustion interne a été traditionnellement réalisée en laboratoires en utilisant des analyseurs de gaz en vrac avec des équipements coûteux. Afin de créer un système capable de réaliser le travail de ces analyseurs, un capteur pouvant détecter plusieurs gaz simultanément est indispensable pour en mesurer la concentration. En effet, utiliser un capteur pour chaque gaz est couteux et peut amener à des procédures complexes d’analyse en raison des différentes technologies utilisées. De plus, l’utilisation de multiples capteurs donne lieu à une perte de ressources financières et humaines. Pour pallier ce problème, une approche alternative proposée dans cette thèse consiste à utiliser un seul capteur pour l’analyse simultanée des différents gaz. Cette approche contribue à réduire la complexité des analyses, la taille et la collecte de données des mesures de gaz mentionnés précédemment. Elle permet également la baisse du coût de l’ensemble du système des mesures.Cette thèse présente la conception, la méthodologie et le développement d’une nouvelle approche pour la mesure de la concentration de gaz utilisant le traitement d’images numériques à travers la modélisation du mélange des couleurs d’émission de lumière dans le tube de décharge de gaz. L’application du modèle inverse permet d’obtenir le pourcentage de chaque gaz dans un mélange contenant jusqu'à quatre gaz connaissant la couleur d’émission du mélange et la couleur d’émission de chaque gaz. Nous discutons aussi le potentiel de certaines méthodes quant à leurs propriétés de miniaturisation et leurs limites. Une comparaison entre les différents capteurs miniaturisés est réalisée en termes suivant la sensibilité, la sélectivité, le coût et d’autres conditions. Pour atteindre les objectifs de recherche, les problèmes techniques rencontrés tels que la modélisation de mélange des couleurs, l’étalonnage de capteurs pour l’acquisition d’images, et le traitement des erreurs de mesures ont été identifiés et des solutions ont été proposéesGases represent one of the most important key measurands in many industrial and domestic activities. The need to detect single gas or a group of gases at the same time varies from one application to another. One of the most important applications of gas sensing is in the concentration measurement of exhaust emissions in internal combustion engines. The variety of gases emitted by these engines and the necessity for a precise measurement of their concentrations are the major incentives for researchers to develop gas sensors that are not only limited to a certain type of gases but to a variety of gases. The most interest gases include CO, NO, NO2, NH4, SO2, CO2, CH4 and other hydrocarbons. These gases can be harmful to human health if present beyond a certain concentration. The analysis of exhaust emissions of internal combustion engines has traditionally been achieved in laboratories using bulk gas analyzers and costly equipments. In order to create a system which can do the work of these analyzers, a sensor that can measure the concentration of multiple gases at the same time is needed. Instead of using a sensor for each gas which is costly and introduce another complexity to the analysis procedure due to the different technologies that are used in the detection of different types of gases. This directly translates into loss of financial and human resources that could otherwise be productively used. In an effort to remedy this situation, this dissertation proposes an alternate approach that uses one sensor to analyze multiple gases simultaneously. This has a significant potential in reducing the aforementioned complexity, size and data collection tasks, and at the same time can lower the cost of the overall system.This dissertation presents the design, methodology, and development of a new method for gas concentration measurement using digital image processing through modeling the color mixing of light emissions in gas discharge tube. The application of the inverse model allows us to get the percentages of each gas in a mixture of up to four gases knowing already the color of emission of the whole mixture and the color of emission of each gas alone. It also discusses the miniaturization potential of some of the methods that are promising in the ability of their miniaturization but suffer from different problems. A comparison is also done among the miniaturized sensors in terms of different parameters like sensitivity, selectivity, cost and other terms. In achieving the research objectives, major technical challenges such as color mixing modeling, imaging sensor calibration, and measurements’ error handling have been successfully identified and addressed
47
Howie, Judith Ann Barnard. "An investigation into the use of fluorescent compounds as detecting materials in a fibre optic anaesthetic gas sensor." Thesis, University of the West of England, Bristol, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387333.
Full text
48
Mufti, Anwar Hassan Ali. "Development of a portable optical sensor for detection of micro-discharges in SFâ†6 switchgear systems." Thesis, University of Salford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239980.
Full text
49
Alfeeli, Bassam. "Miniature gas sensing device based on near-infrared spectroscopy." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/35911.
Full textAbstract:
The identification and quantification of atoms, molecules, or ions concentrations in gaseous samples are in great demand for medical, environmental, industrial, law enforcement and national security applications. These applications require in situ, high-resolution, non-destructive, sensitive, miniature, inexpensive, rapid detection, remotely accessed, real time and continuously operating chemical sensing devices. The aim of this work is to design a miniature optical sensing device that is capable of detecting and measuring chemical species, compatible with being integrated into a large variety of monitoring systems, and durable enough to be used under extreme conditions.
The miniature optical sensor has been realized by employing technologies from the optical communication industry and spectroscopic methods and techniques. Fused silica capillary tubing along with standard communication optical fibers have been utilized to make miniature gas sensor based on near-infrared spectroscopy for acetylene gas detection.
In this work, the basic principles of infrared spectroscopy are reviewed. Also, the principle of operation, fabrication, testing, and analysis of the proposed sensor are discussed in details.Master of Science
50
Malki, Abdelrafik. "Capteurs de vibrations mécaniques et de pression à fibre optique." Châtenay-Malabry, Ecole centrale de Paris, 1993. http://www.theses.fr/1993ECAP0582.
Full textAbstract:
L'utilisation des C. F. O. Couvre de plus en plus d'importants domaines de mesures. Cette thèse reprend dans la première partie l'état de l'art des C. F. O. Nous avons, dans la partie expérimentale effectué des mesures sur un capteur de vibration à fibre optique par effet de speckle, et avons montré au cours des expériences de l'amélioration du rapport signal signal sur bruit, dans le cas d'un filtrage spatial entre deux fibres multimodes différentes. La modélisation et la mise au point d'un capteur de vibrations, de type accéléromètre à fibre optique, par modulation d'intensité, fondé sur le micro-usinage de silicium ont été réalisées, ainsi qu'un prototype. Nous avons montré la faisabilité technologique d'un tel capteur. Celui-ci peut-être intégré dans un réseau à multiplexage chromatique. Le travail a consité également en la mise au point des interfaces optoélectroniques. Enfin un capteur de pression par couplage entre deux fibres a fait l'objet d'une étude théorique, et des mesures expérimentales. Grâce à la fusion des deux fibres optiques, on a amélioré la reproductibilité et la robustesse du capteur. Ceci ouvre ainsi la voie sur un grand nombre d'applications dans le domaine des composants optiques, tels que les coupleurs variables.