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1
Yeung, Anson Chi-Ming Electrical Engineering & Telecommunications Faculty of Engineering UNSW. "Polymer segmented cladding fibres: cross fibre modelling, design, fabrication and experiment." Publisher:University of New South Wales. Electrical Engineering & Telecommunications, 2009. http://handle.unsw.edu.au/1959.4/43656.
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This thesis presents the first research on polymer-segmented-cladding-fibre (PSCF), an emerging class of microstructured- optical-fibres (MOFs), which allows single-mode operation with ultra-large-core area. This research covers the modelling, design, fabrication and experiment of the polymer optical cross-fibre (4-period-SCF) whose cross-sectional view resembles a cross. A new wedge waveguide model has been formulated and applied to demonstrate that for any given parameters, the cross fibre gives the same performance for single-mode operation as the N-period-SCFs (for N = 2, 6 and 8). These fibres behave identically if the high-index segment angle, θ1, is the same and the low-index segment angular width, θ2, is sufficiently large for negligible adjacent mode coupling effects. This remarkable finding has significant ramifications for SCF fabrication, design and performance. Theoretical predictions confirmed by experiments demonstrated that a cross-fibre is all that needed to fabricate a large-core single-mode-fibre with no geometry-induced birefringence. The high-index outer ring effects on the cross fibre single-mode performance have been systematically investigated for the first time. The study reveals that the ring index value higher than its core index has very strong effects on single-mode performance. Within a narrow range of θ1, the minimum fibre length required for single-mode operation is reduced but outside this angle range, longer single-mode length is required. Furthermore, the fibre can be anti-guiding if θ1 exceeds the cutoff angle. Incorporating the fabrication constraints, the optimal cross-fibre design with high-index ring is achieved by optimising the relative index difference, high-index segment angle and core-cladding diameter ratio. Two preform-making techniques developed for the cross-fibres fabrication include the cladding-segment-in-tube method and the core-cladding-segment-in-tube method. The innovative approach in these methods overcomes the problems of bubble formation and fractures, which are related to the fibre structure complexity and the polymer intrinsic properties and their processing. It enables the successful drawing of single-mode fibres. This thesis reports the first experimental demonstration of single-mode operation of large-core cross-fibre. Three experimental studies with different cross-fibre designs have demonstrated (i) large-core single-mode operation, (ii) high-index ring effects on fibre performance and (iii) cross-fibre optimal design trial. Apart from this, the 8-period-SCF fibre performance has been demonstrated experimentally.
2
Chamberlin, Rod. "Dispersion decreasing fibre : fabrication and modelling." Thesis, University of Southampton, 1995. https://eprints.soton.ac.uk/399114/.
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In this thesis the design and fabrication of dispersion decreasing fibres has been investigated. Such novel fibres have a number of novel uses in pulse train generation and loss compensation. The use of fibre diameter control for the production of dispersion decreasing fibres has been investigated. This has proved to be a good technique, and has facilitated the production of a number of useful fibres. A fibre suitable for the generation of 40GHz trains of optical pulses has been produced. This fibre has successfully been used for the generation of optical pulse trains at this data rate. Modelling has been performed to predict the likely propagation characteristics of these pulses. This indicates that propagation with this source is limited to 750km with an amplifier spacing of 30km. The use of dispersion decreasing fibres for loss compensation has been investigated through numerical simulation. The results indicate that there are a number of key high order effects which all affect such fibres. In order for such a dispersion decreasing fibre the initial dispersion must be as low as possible. Further the use of a dispersion flattened preform may also be advisable. Dispersion decreasing fibres have also been used to produce dark soliton trains. The pulses produced have good propagation characteristics over a number of soliton periods. and appear bandwidth limited. The behaviour of the source is shown to be in good agreement with numerical modelling results.
3
Sugden, Kate. "Fabrication and applications of fibre Bragg gratings." Thesis, Aston University, 1996. http://publications.aston.ac.uk/8094/.
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The consequences of fabricating Bragg gratings in various fibres, with or without hydrogen loading, and with varying laser power levels are explored. Three new techniques for fabricating chirped gratings are presented. Beams with dissimilar wavefront curvatures are interfered to give chirped gratings. With the same aim techniques of writing gratings on tapered fibres and on deformed fibres are also covered. With these techniques, a wide variety of gratings has been fabricated from the 'superbroad' (with bandwidths of up to 180 nm), small to medium bandwidth gratings with linear chirp profiles and quadratic chirped gratings. It is demonstrated that chirped grating can be concatenated to form all-fibre Fabry-Perot and Moiré resonators. These are further concatenated with chirped gratings to produce filters with narrow passbands and very broad stopbands. A number of other applications are also addressed. The use of chirped fibre gratings for dispersion compensation and femtosecond chirped pulse amplification is demonstrated. Chirped gratings are used as dispersive elements in modelocked fibre lasers producing ultrashort pulses. A chirped fibre grating Fabry-Perot transmission filter is used in a continuous wave laser that exhibits eleven simultaneously lasing wavelengths. Finally, the use of grating-coupler devices as variable reflectivity mirrors for laser optimisation and gain clamping is considered.
4
Athanasiou, Giorgos S. "The fabrication of chalcogenide glass fibre photonic components." Thesis, University of Nottingham, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606721.
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Photonics is revolutionising the way we live in a similar way to what electronics historically did. The main aim of this PhD project was to investigate and develop fabrication techniques leading to the realisation of mid-infrared photonic components based entirely on chalcogenide glass compositions which were prepared in-house, here at the University of Nottingham, Nottingham, UK. Chalcogenide glasses are based on the chalcogen elements of Group XVI of the Periodic Table and were chosen over conventional silica glass in the work described in this thesis for their significant advantages such as: a wide transmission window, for wavelengths of light from O .5 ~tm up to 25~tm depending on the glass composition, low phonon energies, high non-linearities and high refractive indices. The chalcogenide glass systems of As-Se, Ge-As-Se and Te-As-Se were synthesised and a new quenching technique was developed to prevent ampoule failures. In addition, the distillation of Te-As-Se system was optimised via the use of temperature monitoring. Two simulations were developed using commercial software; the first led to a large mode area, endlessly single mode microstructured optical fibre design and the second verified the photonic band gaps of a photonic band gap fibre from the literature. In particular, a methodology leading to the automation of chalcogenide glass cane drawing, a hot-collapse rig for investigating hot-collapsing of a tube onto a rod and a stacking mechanism for stacking chalcogenide glass canes have all been established as part of fabrication route that has been d~veloped towards the realisation of a chalcogenide glass all-solid core microstructured optical fibre (MOF) comprising 37 core/clad canes based on the design parameters simulated. Furthermore, a robust method for obtaining for the first time multimode optical couplers based on core-clad chalcogenide glass fibre using the method of fibre sidepolishing has been demonstrated experimentally. A key feature is a novel and reproducible procedure developed for obtaining controlled side (D) polishing of chalcogenide glass fibre using an innovative polishing apparatus. These achievements are particularly noteworthy because chalcogenide glass fibre is "more toxic (requiring the use of fume extractors), requires inert atmosphere to prevent oxidation and complicated preparation methods, is difficult to handle and, due to the higher refractive indices, exhibits a higher degree of reflection at glass-air (~20%) interfaces than conventional silica glass fibre. Over the last few years, infrared rnicroscopy (IR) has gained interest and has been used to study cells and tissues for cancer diagnosis. The fabrication of IR-transmitting chalcogenide glass optical fibre tips has been investigated and tips exhibiting reproducible and controlled taper geometries have been demonstrated experimentally. f --- Additionally, methods for metal-coating the tips in a thermal evaporation chamber and cleaving the tips using a focused ion beam (FIB) have been successfully developed. Small diameter tips have been used as an IR probe in scanning near-field infrared microscopy (SNIM) and larger diameter tips for transflection spectroscopy in an attempt to obtain optical and topographical cell tissue data for cell IR fingerprint recognition of Chinese Hamster Ovary cells using synchrotron radiation by employing B22 Beamline of the Diamond Light Source, Oxford, UK. IR spectra was successfully collected and showed good indication of the amide I and amide II bands related with cell DNA.
5
Gillooly, Andrew M. "Advanced Fibre Bragg Grating fabrication systems and devices." Thesis, Aston University, 2005. http://publications.aston.ac.uk/8016/.
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This thesis address the creation of fibre Bragg grating based sensors and the fabrication systems which are used to manufacture them. The information is presented primarily with experimental evidence, backed up with the current theoretical concepts. The issues involved in fabricating high quality fibre Bragg gratings are systematically investigated. Sources of errors in the manufacturing processes are detected, analysed and reduced to allow higher quality gratings to be fabricated. The use of chirped Moiré gratings as distributed sensors is explored, the spatial resolution is increased beyond that of any previous work and the use of the gratings as distributed load sensors is also presented. Chirped fibre Bragg gratings are shown to be capable of operating as in-situ wear sensors, capable of accurately measuring the wear or erosion of the surface of a material. Two methods of measuring the wear are compared, giving a comparison between an expensive high resolution method and a cheap lower resolution method. The wear sensor is also shown to be capable of measuring the physical size and location of damage induced on the surface of a material. An array method is demonstrated to provide a high survivability such that the array may be damaged yet operate with minimal degradation in performance.
6
Yeow, May Ling. "Fabrication of poly(vinylidene fluoride) hollow fibre membranes." Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426179.
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7
Webb, Andrew. "Novel optical fibre fabrication techniques for Yb-doped high-power fibre lasers and sensing applications." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/349228/.
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The work presented in this thesis reports on four novel techniques for fabricating speciality silica preforms and optical fibres. The project aims were to conceive new fabrication methods by adapting conventional Modified Chemical Vapour Deposition (MCVD) and optical fibre drawing equipment, and to demonstrate fibre devices for ytterbium (Yb)-doped high-power fibre lasers (HPFL) and optical sensing applications. Firstly, a new in-situ solution doping technique is presented for fabricating actively-doped fibre-preforms of complex design. The fabrication and characterisation of several multilayered rare-earth (RE)-doped fibres suitable for HPFL applications are reported, including an Yb-doped (>18,000ppm, by weight) fibre with a low effective-NA, which incorporates a pedestal refractive index profile and a unique aluminosilcate (Al:Si) inner-cladding. The vapour-phase deposition of RE ions in fibre-preforms has also been demonstrated using a novel chemical-in-crucible process that is intended for use with precursors of low volatility. Modifications to the standard MCVD setup were made which allows the dopant source to be placed within the substrate glassware and in close proximity to the reaction zone. Preforms with dopant concentrations of up to 25,000 ppm (by weight) of Yb3+ ions have been attained using an organometallic precursor, whilst passive Al:Si preforms containing >16mol% of Al have been achieved using gaseous aluminium chloride. A straightforward fabrication technique for producing silica suspended-core holey fibre (SC-HF) is also presented. The drawn fibre exhibits a relatively low optical loss (of 0.3 dB.m-1 at λ = 1550nm), and the high air-filling fraction, which was predicted as ~30% (for a core size of 0.8μm), is believed to the highest reported value at the time the work was undertaken. The sensing capability of SC-HF has been demonstrated by constructing an all-fibre acetylene-filled gas cell. The final experimental chapter describes the first example of a novel flat fibre concept. Extended lengths of low-loss planar glass substrates were produced using MCVD and conventional fibre drawing equipment. In combination with direct UV-writing, multifunctional planar waveguiding devices can be fabricated that are mechanically flexible. The potential of the flat fibre platform for sensing applications is discussed. The reported fabrication techniques have been implemented through the successful demonstration of several fibre devices suitable for Yb-doped HPFLs and optical sensing applications. The developed techniques have future potential in industry and manufacturing, and it is anticipated that the work presented will enable fibres with novel properties and glass compositions to be researched.
8
Grigoleto, Hayashi Juliano. "Wire Array Infrared Metamaterial Fibres: Fabrication and Applications." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17790.
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Metamaterials are artificial composite materials that exhibit exotic properties due to their components and sub-wavelength structure. During the past decades, several new materials have emerged from this research field with exciting new optical properties and applications. However, the fabrication of certain meta-structures remains a challenge, particularly with low cost and in large volumes. Fibre drawing is an attractive alternative to overcome such problems, but currently fabrication constraints restrict the size of the metal/dielectric drawn structures, limiting their operation to THz frequencies. In this context, this thesis concerns the fabrication, characterization, and use of new soft-glass based wire array metamaterials fibres for applications in the infrared. Numerical modelling of wire array structures is presented to understand which material combinations and structural parameters are more appropriate for infrared metamaterial fibres. The co-drawing process used is described, focusing on the adaptations used to minimize fluctuation of the structure due to fluid dynamics. Metamaterial fibres with uniform structures containing wire diameter and spacing on the order of few hundreds of nm are produced, which are compatible with operation at mid-infrared frequencies. The fabrication of metamaterial fibre tapers with steep transitions, generating hyperlenses, is also demonstrated. Far field imaging is attempted and the challenges regarding subdiffraction imaging are discussed. Feasible alternatives for future far field super-resolution imaging are proposed based on our numerical modelling and the typical structural transitions fabricated. Since the operational range of our hyperlenses is not limited to the infrared, subdiffraction focusing of 1/176 of the operational wavelength is reported at THz frequencies, achieved by combining a polymer hyperlens with our new infrared hyperlens.
9
Cooper, Laurence James. "Fabrication of novel geometry fibre lasers for high power applications." Thesis, University of Southampton, 2005. https://eprints.soton.ac.uk/38958/.
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This thesis details my work on the development of fabrication techniques for high power doped fibre lasers, using novel fibre geometries, and their demonstration. The main methods for increasing output power were using helical cores, multiple cores and large cores. A method for fabricating helical core fibres was proposed and implemented. Core and cladding pumped devices were successfully constructed, and were then tested in collaboration. A cladding pumped helical core fibre laser improved the beam from a 30μm core from an M2 of 3.3 to < 1.4, with a maximum output power of 64W and slope efficiency of 84%. A ribbon fibre with multiple laser emitting cores was fabricated. The difficulties in the fabri- cation of such a fibre required extensive research, and arise from the large aspect ratio of the preform and fibre, and the low size reduction during fibre drawing. Through many steps a ten core ribbon fibre was fabricated, which was used, in collaboration, to achieve an output laser power of 250W, with a slope efficiency of 65%. Using a spectral beam combination technique, 5 cores were locked together. The output from a number of cores within a circular fibre with no combination is a method for attaining stable high powers with moderate beam quality. A three core fibre was fabricated, and showed an M2 of 5 and slope efficiency of 75%. This fibre was then tapered down from 150μm in order to improve the beam quality further, and for 125μm and 100μm tapers, the M2 values measured were improved to 4.3 and 3.5, respectively. An Yb-doped rod was fabricated, with a large core of 140μm diameter, and machined flats to break the cladding symmetry. The power attained was only 13.4W with a slope efficiency of 20%, due to surface imperfections. A fibre created with altered fabrication techniques showed no surface defects and showed over 90% transmission for 800nm light. Experiments performed by a colleague showed a slope efficiency of 69% and an M2 of 11, indicating that the fabrication method could create an effective cladding pumped rod laser.
10
Krishnamurthy, S. "Pre-stressed advanced fibre reinforced composites fabrication and mechanical performance." Thesis, Cranfield University, 2006. http://hdl.handle.net/1826/1039.
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Advanced composite materials have high strength-to-weight ratios, corrosion
resistance and durability and are extensively used in aerospace, energy and defence
industries. This research concentrates on minimising the process-induced residual
stresses, and improving the fibre alignment of composites by employing a fibre prestress
methodology. A novel flat-bed fibre prestress methodology for autoclave processing of composites was developed. This research investigates the effect of fibre prestress on 1)
residual stresses, 2) fibre alignment, 3) static tensile and compression properties and 4)
fatigue behaviour of composites.
Experimental results show that this prestress methodology, on a 16-ply unidirectional E-glass/
913 epoxy composite, reduces the residual strain of the composite from –600 µε to
approximately zero for a prestress of 108 MPa. The strains measured from optical fibre
sensors were in close agreement with those obtained using strain gauge. The results from
fibre alignment studies showed that fibre prestressing improved the fibre alignment from
20% of fibres aligned to 0 ° degree in non-prestressed composites to 75% of fibres aligned
to 0 ° degree in 108 MPa prestressed composites.
Findings have shown that prestressing is beneficial to the static compressive and tensile performance of composites. The results show that fibre prestressing improves the fatigue
life and resistance to stiffness degradation in the low stress level fatigue region. Also a change in static and fatigue damage mechanism was observed. The improvement in the static and fatigue properties is due to the reduction in residual stresses and fibre waviness.
Overall the fibre prestressing methodology enhances the performance of composites by
increasing the resistance to static and fatigue loading. The thesis also suggests that there is an existence of prestress limits to retain optimal material performance.
11
Machavaram, Venkata Rajanikanth. "Micro-machining techniques for the fabrication of fibre Fabry-Perot sensors." Thesis, Cranfield University, 2006. http://dspace.lib.cranfield.ac.uk/handle/1826/1210.
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Fabry-Perot optical fibre sensors have been used extensively for measuring a variety of parameters such as strain, temperature, pressure and vibration. Conventional extrinsic fibre Fabry-Perot sensors are associated with problems such as calibration of the gauge length of each individual sensor, their relatively large size compared to the diameter of optical fibre and a manual manufacturing method that leads to poor reproducibility. Therefore, new designs and fabrication techniques for producing fibre Fabry-Perot sensors are required to address the problems of extrinsic fibre Fabry-Perot sensors. This thesis investigates hydrofluoric acid etching and F2-laser micro-machining of optical fibres to produce intrinsic Fabry-Perot cavities. Chemical etching of single mode fused silica fibres produced cavities across the core of the fibres due to preferential etching of the doped-region. Scanning electron microscope, interferometric surface profiler and CCD spectrometer studies showed that the optical quality of the etched cavities was adequate to produce Fabry-Perot interference. Controlled fusion splicing of etched fibres produced intrinsic Fabry-Perot cavities. These sensors were surface-mounted on composite coupons and their response to applied strain was studied using low coherence interferometry. These sensors showed linear and repeatable response with the strain measured by the electrical resistance strain gauges. To carry out F2-laser micro-machining of fused silica and sapphire substrates, a micro-machining station was designed and constructed. This involved the design of illumination optics for 157 nm laser beam delivery, the design and construction of beam delivery chamber, target alignment and monitoring systems. Ablation of fused silica and sapphire disks was carried out to determine ablation parameters suitable for micro-machining high aspect ratio microstructures that have adequate optical quality to produce Fabry-Perot interference. Cavities were micro-machined through the diameter of SMF 28 and SM 800 fibres at different energy densities. CCD interrogation of these intrinsic fibre cavities ablated at an energy density of 25 x 10 4 Jm -2 produced Fabry-Perot interference fringes. The feasibility of micro-machining high aspect ratio cavities at the cleaved end-face of the fused silica fibres and through the diameter of sapphire fibres was demonstrated. A technique based on in-situ laser-induced fluorescence monitoring was developed to determine the alignment of optical fibres and ablation depth during ablation through the fibre diameter. Ablation of cavities through the diameter of fibre Bragg gratings showed that the heat-generated inside the cavity during ablation had no effect on the peak reflection and the integrity of core and cladding of the fibre. Finally, a pH-sensor, a chemical sensor based on multiple cavities ablated in multimode fibres and a feasible design for pressure sensor fabrication based on ablated cavity in a single mode fibre were demonstrated.
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Wong, Rebecca. "Advanced fibre optic long period grating sensors : design, fabrication and sensing." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/9153.
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This thesis describes the process and technique used to fabricate reproducible optical
fibre long period gratings (LPG) of various types. It explores how they can be
exploited for use as highly selective and sensitive sensors. A versatile method for
fabricating LPG sensors has been demonstrated. The single system has the capability
of fabricating LPGs of different configurations, such as uniform period, those
operating at the phase matching turning point (PMTP), as well as phase shifted
and chirped. LPGs were characterised for their sensitivities to temperature, axial
strain and surrounding refractive index. The gratings at the PMTP were found to
show higher sensitivities to external influences.
Novel sensing configurations that exploit the properties of LPGs were also constructed.
An LPG coated with a molecularly imprinted ceramic coating was demonstrated
to offer a selective method for porphyrin detection. A composite nanoscale
of a titanium oxide (TiO2) matrix and 5, 10, 15, 20 Tetrakis-(N-methyl-piridinium4-
yl)-21H, 23H-porphine tertakis (p-toluenesulfonate) [TMPyP] porphyrin template
film was deposited on the LPG via liquid phase deposition. Attempts to rebind porphyrins
to the matrix were carried out. The LPGs transmission spectrum exhibited
a higher sensitivity to the target TMPyP template than it did to other, structurally
similar porphyrins, showing high selectivity.
A continuously chirped long period grating (CCLPG) sensor for monitoring directional
flow and cure of an epoxy resin is also presented. The asymmetric properties
of the CCLPG were exploited to facilitate the measurement of the direction of the
flow. The CCLPG was also used to monitor changes in the refractive index of the
resin during its cure, showing close agreement with a fibre optic Fresnel refractometer.
13
Machavaram, V. R. "Micro-machining Techniques for the Fabrication of Fibre Fabry-Perot Sensors." Thesis, Cranfield University, 2006. http://hdl.handle.net/1826/1210.
Full textAbstract:
Fabry-Perot optical fibre sensors have been used extensively for measuring a variety of
parameters such as strain, temperature, pressure and vibration. Conventional extrinsic fibre Fabry-Perot sensors are associated with problems such as calibration of the gauge length of each individual sensor, their relatively large size compared to the diameter of optical fibre and a manual manufacturing method that leads to poor reproducibility.
Therefore, new designs and fabrication techniques for producing fibre Fabry-Perot
sensors are required to address the problems of extrinsic fibre Fabry-Perot sensors.
This thesis investigates hydrofluoric acid etching and F2-laser micro-machining of optical fibres to produce intrinsic Fabry-Perot cavities. Chemical etching of single mode fused silica fibres produced cavities across the core of the fibres due to preferential etching of the doped-region. Scanning electron microscope, interferometric surface profiler and
CCD spectrometer studies showed that the optical quality of the etched cavities was
adequate to produce Fabry-Perot interference. Controlled fusion splicing of etched fibres produced intrinsic Fabry-Perot cavities. These sensors were surface-mounted on composite coupons and their response to applied strain was studied using low coherence interferometry. These sensors showed linear and repeatable response with the strain measured by the electrical resistance strain gauges.
To carry out F2-laser micro-machining of fused silica and sapphire substrates, a micro-machining station was designed and constructed. This involved the design of illumination optics for 157 nm laser beam delivery, the design and construction of beam delivery chamber, target alignment and monitoring systems. Ablation of fused silica and sapphire disks was carried out to determine ablation parameters suitable for micro-machining high aspect ratio microstructures that have adequate optical quality to produce Fabry-Perot
interference. Cavities were micro-machined through the diameter of SMF 28 and SM 800
fibres at different energy densities. CCD interrogation of these intrinsic fibre cavities ablated at an energy density of 25 x 10 4 Jm -2 produced Fabry-Perot interference fringes.
The feasibility of micro-machining high aspect ratio cavities at the cleaved end-face of the fused silica fibres and through the diameter of sapphire fibres was demonstrated. A technique based on in-situ laser-induced fluorescence monitoring was developed to determine the alignment of optical fibres and ablation depth during ablation through the fibre diameter. Ablation of cavities through the diameter of fibre Bragg gratings showed that the heat-generated inside the cavity during ablation had no effect on the peak reflection and the integrity of core and cladding of the fibre. Finally, a pH-sensor, a chemical sensor based on multiple cavities ablated in multimode fibres and a feasible design for pressure sensor fabrication based on ablated cavity in a single mode fibre were demonstrated.
14
Ventura, Michael James. "Fabrication and characterisation of three-dimensional passive and active photonic crystals." Swinburne Research Bank, 2008. http://hdl.handle.net/1959.3/35914.
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Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Micro-Photonics, 2008.Submitted for the degree of Doctor of Philosophy, Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, 2008. Typescript. Bibliography: p. 104-118.
15
Devautour, Mathieu. "Etude de fibres actives combinant large coeur et fort niveau de dopage pour l'émission unimodale." Limoges, 2009. https://aurore.unilim.fr/theses/nxfile/default/3fbe2a78-c8d8-4766-9a3b-c7914d7a01eb/blobholder:0/2009LIMO4051.pdf.
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Les lasers à fibre dopée aux ions de terre rare atteignent aujourdh'ui des puissances comparables à celle des lasers massifs. Ces lasers possèdent de nombreux avantages, tels une excellente dissipation thermique, une bonne qualité spatiale de faisceau, une compacité élevée et une très grande robustesse. La montée en puissance de ce type de laser est limitée aujourd'hui, par l'apparition d'effets non linéaires, aux niveaux de puissances actuels, qui perturbent le fonctionnement du laser et dégradent les qualités spatiales et spectrales des faisceaux émis. La plupart des recherches actuelles destinées à repousser ces limitations se concentrent sur l'accroissement de la taille du cœur de la fibre utilisée comme milieu à gain. Cette approche conduit généralement à limiter la concentration en dopant du milieu actif. Une voie alternative est explorée qui consiste à accroître simultanément la surface du cœur de la fibre et la concentration en terre rare du milieu actif. Dans un premier temps, une modélisation numérique complète des oscillateurs lasers continus à fibre dopée aux ions de terre rare est développée et validée expérimentalement. Dans un second temps une fibre combinant large cœur et fort niveau de dopage et offrant une émission unimodale par filtrage des modes d'ordre élevé à l'aide d'une gaine structurée est conçue. Ensuite, deux procédés de fabrication de fibre dopée aux ions de terre rare alternatifs au procédé MCVD sont développés. Le premier, consistant en une vitrification directe de poudre de silice, a permis d'obtenir un matériau de silice dopée à l'ytterbium extrêmement efficace et très homogène en terme d'indice de réfraction. Ce résultat permet d'envisager la fabrication de fibre à large cœur et fort niveau de dopage par ce procédé simple et peu coûteux. Le second, fonctionnant par assemblage étirage multiple, s'est révélé complexe et long à mettre en œuvre. Il n'a pas permis la fabrication d'une fibre offrant une émission unimodale. Cependant, le comportement homogène des matériaux structurés à une période voisine de la longueur d'onde de l'onde lumineuse a pu être vérifié expérimentalementRare earth doped fiber lasers have reached today output power similar to those obtained with others solid state laser. There are numerous assets to use this kind of laser like high efficiency, compactness, high spatial beam quality and excellent thermal properties. Increasing output power encounters today limitation related to the apparition of non linear effects, disturbing the laser behaviour and reducing spatial and spectral beam quality. Most of the researches on this matter focus on finding a way to increase core area of the fiber used as gain medium, leading to limitation on the concentration of rare earth in the active medium. An alternative way trying to increase simultaneously core area and rare earth concentration is explored here. First, full numerical modelisation of fiber laser is conducted and the modelisation is experimentally validated. Then active fiber combining large core and high rare earth concentration for singlemode laser emission working by high order modes filtering with layered cladding has been designed. Then two alternative fabrication process of active fiber alternative to MCVD are developed. The first one, which is direct vitrification of silica powder has produced ytterbium doped silica medium highly homogeneous for refractive index and exhibing high efficiency. This first result allows to consider the fabrication of large and highly doped core fiber with this fabrication process. The second, multi drawing process, has turn up to be long and complex process. It didn't allow to obtained singlemode fiber. Nevertheless, homogeneous behaviour of structured medium for pitch close to the wavelength has been experimentally verified
16
Ross, Steven. "Development of a novel gradient-force tapered fibre optical tweezers system for 3D optical trapping at near horizontal fibre insertion angles." Thesis, Liverpool John Moores University, 2015. http://researchonline.ljmu.ac.uk/4461/.
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The use of optical fibre as a mechanism for the delivery of the trapping laser beam to the sample chamber significantly reduces both the size and the build costs of “Optical Tweezers”. Furthermore, the use of fibre facilitates the decoupling of the optical trapping beam from the microscope optics, which provides further scope for the development of a portable optical trapping system, and the potential for uncomplicated integration with other advanced microscopy systems such as an atomic force microscope (AFM) for example. For use with an AFM, the optical fibre must be inserted at an angle of 10° with respect to the sample chamber floor. However, previous literature suggests that 3D optical trapping with a single fibre inserted at an angle ≤20° is not feasible. This thesis presents the design, development, build and test of a single beam optical fibre based gradient force optical tweezers system and its associated software. An investigation is conducted to ascertain why optical trapping, using single fibre systems, cannot be achieved at sub 20° insertion angles, the result of which formed the basis of a hypothesis that explains this limitation. This finding led to the development of tapered optical fibre tips that are cable of 3D optical trapping at an insertion angle of ≤10°. The optimised optical fibre tapers are presented and their ability to trap both organic and inanimate material in 3D at an insertion angle of 10° is demonstrated. The near-horizontal insertion angle introduced a maximum trapping range (MTR). The MTR of the tips is determined empirically, evaluated against simulated data, and found to be tuneable through taper optimisation. Optical trap characterisation has been undertaken in terms of the optical trapping forces acting on the trapping subjects. Finally, the fibre tapering devices ability to reproduce identical tapers, or not, using the same device parameters, was investigated and the results in terms of geometric profile and optical performance are presented.
17
Mou, Chengbo. "Fabrication and characterisation of 45º and Ex 45º : tilted fibre gratings and their applications in fibre lasers and sensors." Thesis, Aston University, 2012. http://publications.aston.ac.uk/19548/.
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In this thesis, I present the studies on fabrication, spectral and polarisation characterisation of fibre gratings with tilted structures at 45º and > 45º (namely 45º- TFGs and ex 45º-TFGs throughout this thesis) and a range of novel applications with these two types of grating. One of the major contributions made in this thesis is the systematic investigation of the grating structures, inscription analysis and spectral and polarisation properties of both types of TFGs. I have inscribed 45º-TFGs in standard telecom and polarisation maintaining (PM) fibres. Two wavelength regions of interest have been explored including 1.55 µm and 1.06 µm. Detailed analysis on fabrication and characterisation of 45º-TFGs on PM fibres have also been carried out for the first time. For ex 45º- TFGs, fabrication has been investigated only on low-cost standard telecom fibre. Furthermore, thermal responses have been measured and analysed showing that both types of TFG have low responsivity to temperature change. More importantly, their refractive index (RI) responses have been characterised to verify the high responsivity to surrounding medium. Based on the unique polarisation properties, both types of TFG have been applied in fibre laser systems to improve the laser performance, which forms another major contribution of the research presented in this thesis. The integration of a 45º-TFG to the Erbium doped fibre laser (EDFL) enables single polarisation laser output at a single wavelength. When combing with ex 45º-TFGs, the EDFL can be transformed to a multi-wavelength switchable laser with single polarisation output. Furthermore, by utilising the polarisation property of the TFGs, a 45º-TFG based mode locked fibre laser is implemented. This laser can produce laser pulses at femtosecond scale and is the first application of TFG in the field of nonlinear optics. Another important contribution from the studies is the development of TFG based passive and active optical sensor systems. An ex 45º-TFG has been successfully developed into a liquid level sensor showing high sensitivity to water based solvents. Strain and twist sensors have been demonstrated via a fibre laser system using both 45°- and ex 45º-TFG with capability identifying not just the twist rate but also the direction. The sensor systems have shown the added advantage of low cost signal demodulation. In addition, load sensor applications have been demonstrated using the 45º-TFG based single polarisation EDFL and the experimental results show good agreement with the theoretical simulation.
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Dockney, Michael Lee. "Fabrication of wavelength division multiplexed in-fibre Bragg grating arrays for structural monitoring applications." Thesis, Cranfield University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245338.
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Brochu, Guillaume. "Lasers à fibre Fabry-Perot distribués multilongueurs d'onde : modélisation, fabrication et caractérisation." Thesis, Université Laval, 2010. http://www.theses.ulaval.ca/2010/27585/27585.pdf.
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Chisholm, Karen E. "Fabrication and application of short and novel structure in-fibre Bragg gratings." Thesis, Aston University, 2000. http://publications.aston.ac.uk/7993/.
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This thesis presents details on progress made in the fabrication and application of short and novel structure fibre Bragg gratings. The basic theoretical concepts of in-fibre Bragg gratings and photosensitive mechanisms are introduced together with an overview of fabrication methods and applications presented to date. The fabrication of fibre Bragg gratings using a quadrupled Nd:YAG laser is presented and some of the issues of grating fabrication using a fabrication using a phasemask are investigated, including the variation of the separation of the fibre and phasemask, and other alignment issues. A new apodisation technique is presented, enabling the production of gratings with a wide range of spectral profiles. The technique is used to investigate the design and fabrication of length limited fibre Bragg gratings for use in telecommunication systems as filters. Application to devices designed for use in WDM systems is presented. The use of fibre Bragg gratings as high spatial resolution distributed sensors is investigated. Grating sensing arrays comprising very short apodised gratings are demonstrated and Chirped Moiré gratings are implemented as distributed sensors achieving high spatial resolution with miniature point sensing sub-elements. A novel grating sensing element designed to imitate an interferometer is also presented. Finally, the behaviour of gratings fabricated in Boron-Germania-co-doped fibre is investigated, revealing atypical behaviour of the Bragg wavelength during ageing.
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Droushiotis, Nicolas D. "Fabrication and characterization of hollow fibre micro-tubular solid oxide fuel cells." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9779.
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Despite three decades of development of solid oxide fuel cells (SOFCs) since the conception of the tubular Siemens–Westinghouse design, no practical alternatives to yttria-stabilized zirconia (YSZ) and gadolinia-doped ceria (CGO) electrolytes have been established. However, there have been considerable improvements in the performance of SOFCs, decreasing their specific overall costs, by decreasing operating temperatures, understanding their reaction kinetics, increasing specific surface areas of electrode / electrolyte / reactant three-phase boundaries, establishing new fabrication techniques and employing new geometric designs. So called micro-tubular SOFCs (MT-SOFCs) are one of the most promising geometric designs, though a misnomer, as tube diameters are normally several millimetres, significantly smaller than Siemens–Westinghouse SOFCs with 22 mm tube diameters. This three-year Ph. D. project was aiming to establish the feasibility of, and develop, a novel design of SOFC, fabricated using hollow fibres (HFs) with diameters of hundreds of micrometres, thereby increasing the specific surface area of electrodes, increasing the power output per unit volume/mass, facilitating sealing at high temperatures, and decreasing costs. Collaborators used a spinneret in phase inversion process to produce HFs with non-porous, gas-tight cores and porous outer layers ca. 50-100 μm thick; suspensions of YSZ or CGO particles were used to produce the precursor micro-tubes for electrolyte-supported structures. After sintering the HFs, Ni was deposited electrolessly onto their inner surfaces to form Ni-YSZ anodes, using aqueous nickel (II) solutions and (sodium) hypophosphite (H2PO2-) as the reducing agent. With YSZ electrolyte-supported structures, lanthanum strontium manganite (LSM)-YSZ particles were then coated onto outer surfaces of the HFs to form cathodes; these cells produced only 46-400 W m-2 at 800 oC, compared with ca. 800 W m-2 at 600 oC for CGO-supported cells. Anode-supported structures were also produced using non-conductive, porous NiO-YSZ HFs as anode precursors. YSZ particles were suspended in ethanol and electrophoretically deposited (EPD) onto the external surface of NiO-YSZ HFs, requiring electric fields of ca. 22 kV m-1 between a tubular Cu cathode, placed inside the porous HF precursor, and a tubular platinised titanium mesh anode; this implied they had an effective positive charge. The YSZ-coated NiO-YSZ fibres were then co-sintered at 1500 oC. Mixed (YSZ-LSM) and pure LSM cathode layers, for creating functional layers and enhanced current collector electrodes, were deposited using a paint brush and re-sintered at 1200 oC. The resulting anode-supported HF-MT-SOFCs delivered peak power density of 2 kW m-2 at 800 oC. Collaborators then used a triple orifice spinneret in the phase inversion process to co-extrude CGO/NiO-CGO dual layer-HFs, which were then co-sintered. Dispersions of CGO-LSCF particles were then painted or sprayed onto their outer surfaces, as "graded" LSCF-CGO porous cathode precursors that were then sintered at 1200 oC. HF-MT-SOFC fabrication was completed by winding a silver wire current collector spirally round the cathode. Similar arrangements were used for collecting the current from the HF lumen (anode). The use of functional cathode layers, higher porosity anodes, improved anode and cathode current collectors, and optimizing the thickness of the electrolyte layer and operating parameters, enabled maximum power densities of ca. 25 kW m-2 at ca. 600 oC, believed to be a record for a single MT-SOFC. The effects of electrolyte thickness (100-10 μm), cell length (10-50 mm), and anode morphologies / porosities were also determined. HF-MT-SOFCs were found to be stable to reduction/oxidation and thermal cycling for up to 8 days. Finally, a novel design for stacking individual HF-MT-SOFC in series (voltage scale up) and parallel (current scale up) was studied experimentally; 3 HF-MT-SOFCs in parallel delivered ca. 0.67 W (=3.4 kW m-2) at 7.5 kA m-2, 0.45 V and 600 oC.
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Chang, Yuan. "Fabrication and Application of Fibre Bragg Grating Sensors for Monitoring Structural Behaviour." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17597.
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Optical fibre sensors with fibre Bragg grating (FBG) are used widely because of their advantages such as electrical immunity and high sensitivity. The motivation for this thesis is to use the FBG sensors to measure strain gradient and to monitor crack growth, going through the procedures of fabrication and application of fibre FBG sensors for monitoring structural behaviour. The history and advances in FBG sensors are first studied through a literature review, and it highlights several major fabrication methods for the FBG. The FBG sensors used in this study were fabricated using an improved phase mask method. The strains in tensile and bending specimens were successfully measured using both the fabricated and commercial FBG sensors. ABAQUS software was used for simulation of different strain gradient. Spectrum distortion of reflected light was identified by calculating differences in intensity. Furthermore, the coupled mode theory and T-matrix methods were applied to develop an effective model to analyse grating patterns for FBG sensors under strains. Simulation analysis based on MATLAB was performed for the FBG sensors under different strain circumstances. Some strain conditions which were not convenient for the actual test were also analysed using MATLAB and provided a useful reference for studying the FBG sensors under complex strains. Finally, a self-fabricated FBG array was used to monitor mode I interlaminar crack growth in a double cantilever beam (DCB) specimen of glass fibre-reinforced polymer (GFRP) composite. The array with four sets of FBG sensors was attached to the side of cantilever beam of the DCB specimen, the result was analysed, indicating that the array sensor was sensitive to crack growth. This result proved that both the fabrication and the testing method were successful, and attaching FBG sensors on the material surface can be a convenient method for structural health monitoring.
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Kryze, Jana. "Méthode d'élaboration et propriétés mécaniques de composites duralumin / fibres ou particules céramiques, obtenus par métallurgie des poudres et filage." Châtenay-Malabry, Ecole centrale de Paris, 1995. http://www.theses.fr/1995ECAP0444.
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Nous avons mis au point un procédé de fabrication de composites à matrice métallique, dont nous avons montre l'efficacité pour divers renforts céramiques, fibres de carbone, fibres d'alumine saffil, ou particules de carbure de silicium. Nous avons comparé les comportements en traction monotone de ces composites en fonction du type de renfort. L'utilisation de modèles de calcul du type Mori-Tanaka nous a permis de mieux comprendre l'influence des divers paramètres microstructuraux tels que la fraction volumique ou l'orientation des renforts. Nous avons mis en parallèle les résultats d'essais en traction simple, l'observation au microscope de la structure initiale et de la structure endommagée du composite, et l'observation in-situ de l'évolution de l'endommagement. Un traitement thermomécanique de type T351, calqué sur celui de la matrice, permet de tirer parti à la fois du durcissement structural de la matrice et de l'écrouissage élevé induit par les renforts. Le composite renforce par fibres de carbone présente un allongement à la rupture très faible, que nous avons attribué a une faible résistance de l'interface fibre-matrice. Le composite renforcé par fibres d'alumine présente une interface fibre-matrice forte, grâce à la formation de cristaux de spinelles par réaction de l'alumine avec le magnésium de l'alliage. Ceci semble expliquer son bon allongement à rupture. Ce composite présente, en revanche, une réserve de contrainte quasi nulle après le début de la plasticité, et une contrainte à la rupture inferieure a celle de la matrice. Le composite renforcé par particules de carbure de silicium semble le meilleur compromis pour les applications a température ambiante. Un essai comparatif a 180°C montre cependant qu'en température, la limite d'élasticité du composite a renfort particules de sic chute davantage que celle du composite a renfort fibres de carbone
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Lyytik�inen, Katja Johanna. "Control of complex structural geometry in optical fibre drawing." University of Sydney. School of Physics and the Optical Fibre Technology Centre, 2004. http://hdl.handle.net/2123/597.
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Drawing of standard telecommunication-type optical fibres has been optimised in terms of optical and physical properties. Specialty fibres, however, typically have more complex dopant profiles. Designs with high dopant concentrations and multidoping are common, making control of the fabrication process particularly important. In photonic crystal fibres (PCF) the inclusion of air-structures imposes a new challenge for the drawing process. The aim of this study is to gain profound insight into the behaviour of complex optical fibre structures during the final fabrication step, fibre drawing. Two types of optical fibre, namely conventional silica fibres and PCFs, were studied. Germanium and fluorine diffusion during drawing was studied experimentally and a numerical analysis was performed of the effects of drawing parameters on diffusion. An experimental study of geometry control of PCFs during drawing was conducted with emphasis given to the control of hole size. The effects of the various drawing parameters and their suitability for controlling the air-structure was studied. The effect of air-structures on heat transfer in PCFs was studied using computational fluid dynamics techniques. Both germanium and fluorine were found to diffuse at high temperature and low draw speed. A diffusion coefficent for germanium was determined and simulations showed that most diffusion occurred in the neck-down region. Draw temperature and preform feed rate had a comparable effect on diffusion. The hole size in PCFs was shown to depend on the draw temperature, preform feed rate and the preform internal pressure. Pressure was shown to be the most promising parameter for on-line control of the hole size. Heat transfer simulations showed that the air-structure had a significant effect on the temperature profile of the structure. It was also shown that the preform heating time was either increased or reduced compared to a solid structure and depended on the air-fraction.
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Lyytikäinen, Katja Johanna. "Control of complex structural geometry in optical fibre drawing." Thesis, The University of Sydney, 2004. http://hdl.handle.net/2123/597.
Full textAbstract:
Drawing of standard telecommunication-type optical fibres has been optimised in terms of optical and physical properties. Specialty fibres, however, typically have more complex dopant profiles. Designs with high dopant concentrations and multidoping are common, making control of the fabrication process particularly important. In photonic crystal fibres (PCF) the inclusion of air-structures imposes a new challenge for the drawing process. The aim of this study is to gain profound insight into the behaviour of complex optical fibre structures during the final fabrication step, fibre drawing. Two types of optical fibre, namely conventional silica fibres and PCFs, were studied. Germanium and fluorine diffusion during drawing was studied experimentally and a numerical analysis was performed of the effects of drawing parameters on diffusion. An experimental study of geometry control of PCFs during drawing was conducted with emphasis given to the control of hole size. The effects of the various drawing parameters and their suitability for controlling the air-structure was studied. The effect of air-structures on heat transfer in PCFs was studied using computational fluid dynamics techniques. Both germanium and fluorine were found to diffuse at high temperature and low draw speed. A diffusion coefficent for germanium was determined and simulations showed that most diffusion occurred in the neck-down region. Draw temperature and preform feed rate had a comparable effect on diffusion. The hole size in PCFs was shown to depend on the draw temperature, preform feed rate and the preform internal pressure. Pressure was shown to be the most promising parameter for on-line control of the hole size. Heat transfer simulations showed that the air-structure had a significant effect on the temperature profile of the structure. It was also shown that the preform heating time was either increased or reduced compared to a solid structure and depended on the air-fraction.
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Wu, Jiali. "Fabrication and characterisation ceramic matrix continuous fibre reinforced composites by sol-gel processing." Thesis, University of Sheffield, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387765.
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Alric, Jérôme. "Synthèse d’oligomères α-fluoroacryliques photoreticulables : application à la fabrication de fibre optique plastique." Montpellier 2, 2001. http://www.theses.fr/2001MON20054.
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Silva, Deborah Desimone. "Fabrication and characterisation of oxide fibre-reinforced glass matrix composites for optomechanical applications." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6414.
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Stiff and strong ceramic fibres have been incorporated into brittle glass matrices in order to increase their mechanical strength and fracture toughness. In the present work, a novel processing technique has been investigated, in which the reinforcing fibres are “sandwiched” unidirectionally between glass slides and heat-treated for consolidation into composites by viscous flow of the glass matrix, filling the gaps between the reinforcing fibres. Highly dense and transparent composites were produced combining alumina (Nextel ™) or sapphire fibres with soda-lime silicate or borosilicate glasses. Their microstructural, optical and mechanical properties were investigated and compared to those of the unreinforced glass matrix processed under the same conditions. Moreover, a sol-gel technique was developed for coating the fibres with a ZrO2 interfacial layer. As-received and ZrO2 coated Nextel ™ and sapphire fibre-reinforced composites were produced, with fibre contents of up to 1 vol. % and total light transmittance in the range of 70 to 93 % of the matrix transmittance. Sapphire fibre-reinforced borosilicate glass composites exhibited the highest measured flexural strength (73 MPa), followed by ZrO2 coated Nextel ™ fibre-reinforced soda-lime silicate composites (0.6 vol. %), which exhibited mean flexural strength of 64 MPa. The introduction of a ZrO2 interfacial layer effectively increased the flexural strength of the composites compared to the unreinforced matrix and the as-received fibre-reinforced composites. In addition, there was evidence of fibre pullout and crack deflection upon failure during flexural and fracture toughness tests, as well as a fail-safe behaviour upon flexure, which enabled the composites to retain their integrity. A robust processing methodology was thus demonstrated of producing high quality oxide fibre-reinforced glass matrix composites, with high optical transparency and favourable fracture properties. The composites produced are promising materials for a wide range of applications, notably in the construction industry, special machinery and architecture.
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De, Valicourt Guilhem. "Conception, fabrication, et évaluation de modulateurs déportés pour les réseaux d'accès et radio sur fibre." Phd thesis, Télécom ParisTech, 2011. http://pastel.archives-ouvertes.fr/pastel-00677397.
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L'évolution des outils télécommunicationnels répond à une révolution des usages. Les réseaux d'accès et de type radio-sur-fibre doivent répondre à cette demande de l'utilisateur final et le déploiement massif de la fibre optique confirme cette évolution. Dans cette perspective, l'utilisation du multiplexage en longueur d'onde (largement utilisé dans les réseaux cœurs) est maintenant considérée dans le cas d'une augmentation du débit chez l'utilisateur. Néanmoins de nouvelles problématiques, propres à ces réseaux, émergent, telles que le coût pour l'abonné. De nouveaux composants indépendants de la longueur d'onde sont donc nécessaires pour réduire les coûts de déploiement tout en apportant flexibilité et facilité de gestion de ce type de réseaux. Les modulateurs déportés (ou RSOA) sont une solution répondant à ces exigences mais ils doivent se plier à celles, nouvelles, des réseaux d'accès et des réseaux radio-sur-fibre. Cette thèse propose une étude détaillée des propriétés physiques de ces composants ainsi que de ces applications en tant qu'émetteur indépendant de la longueur d'onde dans plusieurs configurations réseaux. Les notions fondamentales nécessaires à la compréhension de ces travaux seront abordées ainsi que la conception et la fabrication de ces composants en salle blanche. Une analyse des performances statiques et dynamiques des composants en fonction de certains paramètres clefs tels que le confinement optique, la longueur de la zone active et la réflectivité des facettes est détaillée. La théorie, une modélisation et des mesures expérimentales seront utilisées pour la création de composants optimisés ayant des performances conformes à l'état de l'art. De nouvelles configurations de RSOA à deux électrodes seront proposées pour diverses utilisations originales de ces composants. Finalement, une étude système viendra compléter notre analyse pour des applications concernant les réseaux d'accès et les réseaux de type radio-sur-fibre.
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Gagné-Godbout, Léonard. "Modélisation, fabrication et caractérisation d'un amplificateur à fibre optique à sept coeurs dopés à l'erbium." Thesis, Université Laval, 2014. http://www.theses.ulaval.ca/2014/30651/30651.pdf.
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Les fibres à cœurs multiples sont une avenue intéressante pour répondre à la demande croissante des taux de transferts de données via la fibre optique. Pour que cette approche soit réalisable, plusieurs composants multicoeurs seront nécessaires dont des amplificateurs pour permettre la transmission sur de longues distances. Le but de ce mémoire est de concevoir, fabriquer et tester un amplificateur à cœurs multiples dopés à l’erbium (MC-EDFA). D’abord, la théorie de base reliée à l’opération des amplificateurs à fibre dopées à l’erbium (EDFA) sera présentée et expliquée. Avec ces notions théoriques, un outil de simulation permettant de simuler les performances d’un EDFA a été développé et implémenté dans MATLAB. Pour établir un protocole expérimental et se familiariser avec les fibres dopées à l’erbium, un amplificateur standard à un seul cœur, dont les paramètres ont été définis à l’aide du simulateur, a été fabriqué avant de procéder à la fabrication de l’amplificateur à cœurs multiples. Une caractérisation complète de cet amplificateur a été faite. Les résultats de cette caractérisation seront présentés et comparés à des simulations pour valider du même coup l’outil de simulation. Le mémoire se poursuivra par la présentation du design et de la fabrication d’un MC-EDFA à sept cœurs. Les paramètres des cœurs sont les mêmes que ceux de l’EDFA caractérisé auparavant. Donc, la caractérisation de l’EDFA aura aussi servi à définir les paramètres des cœurs du MC-EDFA. L’approche utilisée pour multiplexer les signaux dans la fibre, qui a été un obstacle majeur à la prise de données expérimentales, sera ensuite présentée. Pour finir, les mesures expérimentales prises sur les sept cœurs seront présentées pour évaluer les performances du MC-EDFA. Bien que le MC-EDFA possède une double gaine permettant d’injecter la pompe dans la gaine interne, toutes les données expérimentales ont été prises avec la pompe injectée directement dans chaque cœur. Des difficultés techniques, qui seront expliquées dans le dernier chapitre, ont rendu impossible la prise de mesures avec un schéma de pompage dans la gaine.
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Valicourt, Guilhem de. "Conception, fabrication et évaluation de modulateurs déportés pour les réseaux d'accès et radio sur fibre." Paris, Télécom ParisTech, 2011. https://pastel.hal.science/pastel-00677397.
Full textAbstract:
L’évolution des outils télécommunicationnels répond à une révolution des usages. Les réseaux d’accès et de type radio-sur-fibre doivent répondre à cette demande de l’utilisateur final. Dans cette perspective, l’utilisation du multiplexage en longueur d’onde est maintenant considérée dans le cas d’une augmentation du débit chez l’utilisateur. De nouveaux composants indépendants de la longueur d’onde sont donc nécessaires pour réduire les coûts de déploiement tout en apportant flexibilité et facilité de gestion de ce type de réseaux. Les modulateurs déportés (ou RSOA) sont une solution répondant à ces exigences mais ils doivent se plier à celles, nouvelles, des réseaux d’accès et des réseaux radio-sur-fibre. Cette thèse propose une étude détaillée des propriétés physiques de ces composants ainsi que de ces applications en tant qu’émetteur indépendant de la longueur d’onde dans plusieurs configurations réseaux. Les notions fondamentales nécessaires à la compréhension de ces travaux seront abordées ainsi que la conception et la fabrication de ces composants en salle blanche. Une analyse des performances statiques et dynamiques des composants en fonction de certains paramètres clefs tels que le confinement optique, la longueur de la zone active et la réflectivité des facettes est détaillée. La théorie, une modélisation et des mesures expérimentales seront utilisées pour la création de composants optimisés ayant des performances conformes à l’état de l’art. De nouvelles configurations de RSOA à deux électrodes seront proposées pour diverses utilisations original de ces composants. Finalement, une étude système viendra compléter notre analyseFibre-to-the premises (FTTP) is considered as the main solution in order to satisfy the demand for higher capacity networks. For next-generation access networks, upgradeability and high capacity could be obtained using Wavelength-Division Multiplexing in PON (WDM-PON). However, cost and compatibility with existing TDM-PON networks is still an important issue. If wavelengths are to be dynamically allocated, one to each RAU, colorless devices are needed in order to minimize the deployment cost. Reflective Semiconductor Optical Amplifier (RSOA) devices can be used as a low-cost solution due to their wide optical bandwidth. In this study, RSOAs are optimized for WDM PON and R-o-F access technology. The design, fabrication and system evaluation are presented. This study oscillates between a theoretical approach, a modeling of the physical mechanisms as well as experimental measurements. 2-section RSOAs are also investigated. Finally, the envisaged architectures of access and RoF networks based on optimized RSOA are evaluated
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Gagné-Godbout, Léonard. "Modélisation, fabrication et caractérisation d'un amplificateur à fibre optique à sept cœurs dopés à l'erbium." Master's thesis, Université Laval, 2014. http://hdl.handle.net/20.500.11794/25152.
Full textAbstract:
Les fibres à cœurs multiples sont une avenue intéressante pour répondre à la demande croissante des taux de transferts de données via la fibre optique. Pour que cette approche soit réalisable, plusieurs composants multicœurs seront nécessaires dont des amplificateurs pour permettre la transmission sur de longues distances. Le but de ce mémoire est de concevoir, fabriquer et tester un amplificateur à cœurs multiples dopés à l’erbium (MC-EDFA). D’abord, la théorie de base reliée à l’opération des amplificateurs à fibre dopées à l’erbium (EDFA) sera présentée et expliquée. Avec ces notions théoriques, un outil de simulation permettant de simuler les performances d’un EDFA a été développé et implémenté dans MATLAB. Pour établir un protocole expérimental et se familiariser avec les fibres dopées à l’erbium, un amplificateur standard à un seul cœur, dont les paramètres ont été définis à l’aide du simulateur, a été fabriqué avant de procéder à la fabrication de l’amplificateur à cœurs multiples. Une caractérisation complète de cet amplificateur a été faite. Les résultats de cette caractérisation seront présentés et comparés à des simulations pour valider du même coup l’outil de simulation. Le mémoire se poursuivra par la présentation du design et de la fabrication d’un MC-EDFA à sept cœurs. Les paramètres des cœurs sont les mêmes que ceux de l’EDFA caractérisé auparavant. Donc, la caractérisation de l’EDFA aura aussi servi à définir les paramètres des cœurs du MC-EDFA. L’approche utilisée pour multiplexer les signaux dans la fibre, qui a été un obstacle majeur à la prise de données expérimentales, sera ensuite présentée. Pour finir, les mesures expérimentales prises sur les sept cœurs seront présentées pour évaluer les performances du MC-EDFA. Bien que le MC-EDFA possède une double gaine permettant d’injecter la pompe dans la gaine interne, toutes les données expérimentales ont été prises avec la pompe injectée directement dans chaque cœur. Des difficultés techniques, qui seront expliquées dans le dernier chapitre, ont rendu impossible la prise de mesures avec un schéma de pompage dans la gaine.
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Gwandu, B. A. L. "Design and fabrication of advanced fibre gratings and their applications to sensing instrumentations and telecommunications." Thesis, Aston University, 2003. http://publications.aston.ac.uk/8004/.
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Lavoute, Laure. "Conception et fabrication d'une fibre unimodale à gaine résonante combinant large coeur et fort niveau de dopage." Limoges, 2007. https://aurore.unilim.fr/theses/nxfile/default/270a2199-24b1-4c40-beb4-cd2f324542a7/blobholder:0/2007LIMO4051.pdf.
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Le transport et la génération de forte puissance dans les fibres optiques sont aujourd’hui principalement limités par les effets non linéaires et problèmes thermiques engendrés par des densités de puissance trop importantes. Les structures originales de types LHDC (« Large and Highly Doped Core ») présentées pour la première fois dans ce manuscrit, permettent de s’affranchir de ces contraintes en combinant un large cœur (grande aire modale) et un fort niveau de dopage (faible longueur d’interaction). Le cœur actif est entouré d’une gaine résonante d’inclusions haut indice générant, via des couplages intermodaux optimisés, la délocalisation de l’énergie de l’ensemble des modes d’ordres supérieur supportés par le cœur tout en préservant le confinement du mode fondamental. Ce filtrage modal original favorise la discrimination par le gain de l’unique mode fondamental, garantissant ainsi la qualité spatiale du faisceau émisPropagation and generation of high power in optical fibre are mainly limited by the nonlinear and thermal effects occurring when power density is too high. The original LHDC structures ("Large and Highly Doped Core") presented for the first time in this manuscript, can escape these limiting factor by combining a large core (i. E. Large mode area) and a high doping level (i. E. Low fibre length). The active core is surrounded by a resonant cladding made of high index inclusions. Thanks to optimized coupling relation between the core and the cladding rods, energy of high order modes of the core spreads over the cladding when the fundamental mode remains confined in the active region. This original modal filtering combined to gain discrimination guarantees the quality of spatial beam
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He, Qinghao. "Structure-property Relationship of 3D Printed Polymers and Fibre-reinforced Composites." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/24365.
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Fused filament fabrication (FFF) has been utilised in various applications as it provides a cost-effective and flexible method to fabricate products in low volume. In carrying out both microstructural and mechanical characterisations, this study systematically elaborates the process-structure-property relationships of 3D printed thermoplastics, short fibre reinforced polymers and continuous fibre-reinforced polymer composites fabricated by the FFF process. The work is of great importance as it yields in-depth insight into the mechanisms of the novel manufacturing process, providing valuable guidance to improve the process so that high-performance parts can be fabricated and used in applications with critical load-bearing capacity requirements. This study starts from comprehensive experimental investigations into 3D printed bulk specimens of semi-crystalline polymers and short fibre reinforced polymer composites, respectively, with structural analyses performed to characterise the mechanisms of the FFF process. It is found that the mechanical properties of the printed materials suffer a dramatic loss in elastic modulus and strength compared with the benchmark materials with further compression moulding (CM) process. There is an urgent need for a method to accurately characterise the fusion bonding formed between individual filaments during the FFF process. Hence, a novel approach based on the essential work of fracture (EWF) concept was developed and examined in this study, to quantify fusion bonding by determining the value of specific essential work of fracture (w_e). The difference in fusion bonding between the in-plane deposition mode and the in-thickness deposition mode was identified. Additionally, compared with the results of experimental characterisation for printed films with further CM, the dramatically decreased values of w_e and its coefficient of determination (R2) of the 3D printed films indicated the formation of poor fusion bonding during the FFF process. The EWF method was then extended to characterise the fusion bonding between individual filaments of 3D printed short carbon fibre reinforced polyamide 6 (SCF/PA6) composite films fabricated in the two deposition modes. The fusion bonding in the in-thickness mode was found to be much weaker than that in the in-plane mode, a result not only of the narrower processing window but also of the formation of voids between the filaments. In-depth studies were performed to reveal the effects of short fibres on the specific essential work of fracture of the 3D printed composites, addressing the complex relationships between the matrix, fibre-matrix interfaces, fibre orientation, etc. Continuous carbon fibre reinforced polymer composites with significantly improved mechanical performance were fabricated using the FFF process followed by comprehensive characterisations. In comparisons with the benchmark with further CM, the tensile, flexural and Mode I interlaminar fracture properties of the 3D printed composites showed a considerable amount of reduction because of the formation of microscopic voids. Further investigations of the substantial impact of voids on failure mechanisms were undertaken by microstructural analyses, with factors contributing to the formation of voids identified. A discussion of the quality of fusion bonding for printed thin composite films was also presented to highlight the issues. A dynamometer was successfully integrated with a 3D printing platform to achieve in-process monitoring of three-dimensional forces applied during the deposition process, providing much deeper understanding of the process-structure-property relationships by analysing a mechanistic model of intimate contact and autohesion. It was found that the compaction force played a critical role in determining the printing quality of the printed parts. This part of the study also highlighted the possibility of achieving intelligent manufacturing by integrating smart sensors into the FFF process.
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Hao, Ying. "Design, fabrication and characterisation of polymer based wavelength-division-multiplexing filters for fibre-to-the-home application." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610110.
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Bouslimani, Yassine. "Filtrage en longueur d'onde par fibre optique monomode." Rouen, 1999. http://www.theses.fr/1999ROUES024.
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Le travail présenté dans cette thèse est consacré au filtrage en longueur d'onde par fibre optique monomode. L'étude théorique est consacrée au phénomène de propagation dans des structures particulières de fibres optiques. Différentes approches sont présentées pour la résolution de l'équation de propagation. La simulation dans des structures biconiques par couplage de modes est effectuée pour une gaine finie en tenant compte de l'indépendance des variations des rayons du CuR et de la gaine. Les solutions des équations de couplage ont été calculées analytiquement et numériquement. La représentation tridimensionnelle de ces solutions a permis d'observer le comportement oscillatoire de la réponse spectrale en longueur d'onde. La fabrication des composants est effectuée en utilisant un laser CO2. Ceci a permis de réaliser des profils de biconiques de quelques centaines de micromètres de longueur avec une bonne maîtrise du procédé de fabrication. Les structures ainsi réalisées sont caractérisées et leurs réponses en longueur d'onde présentent des périodes d'oscillations faibles. Les filtres optiques en longueur d'onde ont été réalisées par trois techniques de filtrage utilisant les structures biconiques.
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Rugbani, Ali. "Investigating the influence of fabrication parameters on the diameter and mechanical properties of polysulfone ultrafiltration hollow-fibre membranes." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2677.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2009.ENGLISH ABSTRACT: Polysulfone hollow-fibre membranes were fabricated via the dry-wet solution spinning technique. The objective was to demonstrate the influence of the various fabrication parameters on the diameter and mechanical properties of the hollow-fibre membranes and to optimize the spinning process by controlling these parameters with a computer control system. The effects of the operation parameters were investigated using an experimental design based on a fractional factorial method (Taguchi’s design of experiments). The parameters that were considered are the spinneret size, dope solution temperature, bore fluid temperature, coagulation bath temperature, dope extrusion rate, bore flow rate and the take-up speed. A new pilot solution spinning plant was installed and upgraded, and a computer control system, based on LabView, was developed to control, monitor and log the experimental data. The diameter of the hollow-fibres were determined using a scanning electron microscope (SEM) while the mechanical properties were measured using a tensile tester. The effects of diameter size and wall thickness of the hollow-fibres on the performance of the membranes were studied. The results showed the significance of the fabrication parameters that dominate the diameter and strength of the hollow-fibres.
AFRIKAANSE OPSOMMING: Polisulfoon holvesel membrane is met ‘n droë-nat oplossingspin proses vervaardig. Die doel hiermee was om die invloed van verskeie vervaardigingsparameters op die deursnee en meganiese eienskappe van die holvesel membrane te demonstreer asook om die spin proses te optimeer deur gerekenariseerde beheer van die aanleg. ‘n Eksperimentele ontwerp, gebaseer op ‘n gedeeltelike faktoriaal metode (Taguchi se eksperimentele ontwerp) is gebruik om die invloed van die vervaardigingsparameters te ondersoek. Die parameters wat oorweeg is, is spindop grootte, materiaal temperatuur, boorvloeistof temperatuur, stolbad temperatuur, materiaal ekstrusie tempo and opwen spoed. ‘n Nuwe oplossingspin loodsaanleg was geïnstalleer en opgegradeer en ‘n rekenaar beheerstelsel, gebaseer op LabView, is ontwikkel om die aanleg te beheer, moniteer en eksperimentele data te stoor. Die deursnee van die holvesel is gemeet met ‘n skanderingelektron mikroskoop (SEM) terwyl die meganiese eienskappe bepaal is met ‘n trektoets apparaat. Die effek van die deursnee en wanddikte van die holvesels op die werkverrigting van die membrane is ook bestudeer. Die resultate toon watter vervaardigingsparameters is beduidend vir die deursnee en sterkte van die holvesels.
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Leong, Julie Yeen Yeen. "Fabrication and applications of lead-silicate glass holey fibre for 1-1.5 microns : nonlinearity and dispersion trade offs." Thesis, University of Southampton, 2007. https://eprints.soton.ac.uk/50197/.
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This thesis describes the development of novel microstructured optical fibres (MOFs), namely holey optical fibres (HFs), based on a commercial highly nonlinear non-silica glass: By taking the advantages of the zero dispersion of the HFs at 1 μm and 1.55 μm, the SC studies are carried out using these HFs (WW HFs and SEST HFs). Both of the fibre SC studies combined experimental and numerical results, and the simulations and experiments were in qualitative agreement. We observed a spectrum spanning over 1000nm by using just ~98 pJ energy pulses in a 60cm piece of the WW HF. This demonstrated the advantage of SG-HFs in terms of compact devices and low power requirements.
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Singery, Vicky. "C-Ply (Trademark) NCF Carbone extra fin : Etude du procédé de fabrication et optimisation du renfort." Thesis, Mulhouse, 2016. http://www.theses.fr/2016MULH8973.
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L’industrie aéronautique travaille sur l’amélioration des systèmes propulsifs parl’introduction de composites dans la fabrication des aubes de soufflante afin d’alléger lastructure et ainsi de réduire la consommation en carburant des avions. Ces pièces réaliséesen tissage 3D présentent généralement des irrégularités de surface. Une manière d’optimisercet aspect est d’ajouter un pli additionnel de surface : nos travaux de thèse portent sur ledéveloppement de ce pli sous la forme d’un renfort « Non Crimp Fabric » (NCF) biaxial extrafinen fibre de carbone de module intermédiaire (IM), inférieur à 100 g/m², régulier et ayant unebonne déformabilité. Lors de nos travaux de thèse, nous avons utilisé la méthode des plans d’expériencepour améliorer la technologie d’étalement afin de répondre aux exigences demandées. Nousavons pu définir la configuration optimale d’étalement permettant d’atteindre la cible d’un pliinférieur à 50 g/m² en fibre de carbone IM. Pour réaliser un NCF extra-fin, après étalement,les plis sont assemblés par couture afin d’assurer la tenue du renfort. La combinaison decouture choisie (armure, tension, longueur, jauge …) conditionne l’aspect du NCF et sacapacité à être manipulée et déformée. Nous avons donc optimisé les paramètres de coutureafin d’obtenir les propriétés souhaitées. Après avoir optimisé l’étalement des fibres et l’assemblage des plis, nous avons réalisé et caractérisé les renforts NCF extra-fins pour valider leurs propriétés. Nous sommesfinalement parvenus à mettre au point un renfort NCF en fibre de carbone IM, inférieur à50 g/m² par pli ayant un taux de couverture supérieur à 98 % et une bonne capacité à sedéformerAircraft manufacturers are working on the improvement of their engines bymanufacturing fan blades with advanced composite materials to reduce fuel consumption.However, fan blades are made from 3D woven fabrics which often have surface irregularities.It can be minimized by an additional thin layer on the surface : our thesis work is focused onthe development of a new textile structure based on ultra-thin biaxial “Non Crimp Fabric” (NCF)technology. This spread NCF made from intermediate modulus (IM) carbon fibers must belighter than 100 gsm, regular and deformable.During our thesis work, we used Design of Experiments (DOE) methodology to improvethe spreading technology used by Chomarat to make ultra-light NCF materials and meet theestablished requirements. We were able to reach the ultra-thin ply target of less than 50 gsmper ply. After optimizing the spreading process these thin ply tapes are stitched together tocreate NCF. Stability, visual aspect, handling and deformability are dependent on the stitchingsettings (stitching pattern, tension, length, gauge, etc.). Therefore we optimized the stitchingparameters to get the desired properties.After the spreading and stitching process had been optimized, the NCF weremanufactured and tested to validate the desired properties had been achieved. The testingconfirmed that we were able to develop a new carbon fiber NCF that was less than 50 gsm perply, had a coverage rate of higher than 98 % and had good deformability characteristics
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Scarpignato, Gerardo Cristian. "Conception, fabrication et caractérisation d'un amplificateur de puissance à base de verres spéciaux pour les sources LIDAR." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT008.
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L'objectif de ce travail de recherche est l'étude, la réalisation et la caractérisation d'un amplificateur de puissance à base de verres spéciaux devant être inséré dans un dispositif laser impulsionnel à cohérence élevée opérant a la longueur d'onde de 1550 nm en configuration MOPA (Master Oscillator Power Amplifier). Il aura pour fonction d'amplifier le signal provenant d'un laser source afin de pouvoir le propager sur des distances élevées sans pour autant dégrader ses caractéristiques spectrales ou sa cohérence. Le dispositif ainsi obtenu sera utilisé comme source laser pour des systèmes LIDAR compact pouvant soit être embarqués à bord d'avions ou de voitures; soit être utilisés dans des stations météorologiques ou des aéroports. Un tel projet représente une innovation majeure dans le domaine des capteurs laser fonctionnant en espace libre. Il s'agit en effet de réaliser des dispositifs compacts qui n'existent pour l'instant pas aussi bien de façon commerciale que des les laboratoires de rechercheThe objective of the present research is the study, fabrication and characterization of a power amplifier based on special glasses to be implemented as an embedded module inside a pulsed laser device with high coherence working at 1550 nm wavelength. The optical amplifier represents the second module of a laser in configuration MOPA (Master Oscillator Power Amplifier). The device must amplify the signal proceeding from a seed laser and allow the propagation of the signal at high distances while maintaining the spectral characteristics of the high coherent source. The device obtained with this approach will be employed as a source for a monitoring LIDAR system, which will be installed in train monitoring portals. The results can be extended to other applications as well, such as aeroplanes, meteorological stations or airports. The current research work is intended to contribute to the fabrication of compact devices that seems not be still available even in laboratories
Lo scopo della presente ricerca `e lo studio, la realizzazione e la caratter-izzazione di un amplificatore di potenza a base di vetri speciali da utiliz-zare come modulo da implementare all’interno di un dispositivo laser adimpulsi ad elevata coerenza operante alla lunghezza d’onda di 1550 nm.L’amplificatore ottico rappresenta il secondo modulo di un laser in configu-razione MOPA (Master Oscillator Power Amplifier): esso ha la funzione diamplificare il segnale proveniente da un laser “seed” e permette di propa-gare il suo segnale ad elevate distanze, mantenendo tuttavia le caratteris-tiche spettrali di elevata coerenza della sorgente. Il dispositivo cos`ı ottenutosar`a utilizzato come sorgente per un sistema LIDAR di rilevazione a bordodi aerei, autoveicoli e stazioni meteorologiche o aeroporti. Questi sistemisembrano non essere ancora disponibili neanche a livello dei laboratori diricerca
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Le, Bouffant Jean. "Étude de l'excentricité d'une fibre optique dans son revêtement époxy-acrylate et réalisation d'un dispositif de mesure en temps réel." Paris 11, 1986. http://www.theses.fr/1986PA112270.
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Cette thèse a pour objet la détermination d'une méthode de mesure rapide et non-destructive du défaut de centrage d'une fibre optique dans son revêtement époxy-acrylate et la réalisation d'un dispositif de mesure en temps réel, utilisable en ligne sur la tour de fibrage. Une analyse, à l'aide d'un modèle de rayons optiques, du champ diffracté "vers l'avant" par la fibre éclairée transversalement, permet de mettre en évidence l'existence de maxima secondaires de lumière et de relier leur position angulaire à l'excentricité. Une relation simple est établie entre la position angulaire de ces pics, la valeur du module, de la direction du défaut de centrage et du rapport des diamètres gaine optique-enduction ; rendant ainsi possible la détermination de ces trois paramètres. Une vérification expérimentale est présentée et confirme la validité du modèle employé. L'appareil de mesure en temps réel que nous avons mis au point, permet de délivrer à une fréquence de cinq Hertz les trois grandeurs recherchées avec une précision respectivement de 1 micron, 5 degrés, et 1. 5 pour cent. Les résultats expérimentaux obtenus à l'aide de cet appareil sont discutés.
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Michaud, Bernard. "Etude de l'orientation de fibres céramiques sous champ magnétique : application à l'élaboration de matériaux composites à matrice métallique." Phd thesis, Université Sciences et Technologies - Bordeaux I, 1998. http://tel.archives-ouvertes.fr/tel-00169119.
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Létude concerne une voie originale d'élaboration de matériaux composites à matrice métallique a propriétés structurales anisotropes. Elle consiste a orienter le renfort fibreux discontinu par l'action d'un champ magnétique intense et homogène. Afin de déterminer les paramètres d'orientation influents, l'équation du mouvement d'une fibre dans un fluide visqueux a été établie. Sa vérification a nécessité la réalisation d'un dispositif expérimental original. Trois couples fibres/matrice significatifs ont ete choisis (C/Cu, C/Ti, Al2O3/Ni). La mise en oeuvre du matériau composite par métallurgie des poudres implique la réalisation préalable, sous champ magnétique, de preimprégnés orientés. Les caractérisations physico-chimiques, thermiques et mécaniques entreprises montrent que les matériaux composites élaborés par cette voie présentent les caracteristiques anisotropes attendues.
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Wilkinson, Peter John. "Novel mechanical alignment and component fabrication for wavelength-selective optical switches." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277801.
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Lentsolo, Yalli Gym Clerc. "Synthèse et utilisation de fibres cellulosiques phosphatées pour la valorisation de la fibre végétale dans l'amélioration des propriétés de surface du papier et la fabrication de matériaux ignifuges." Thèse, Université du Québec à Trois-Rivières, 2013. http://depot-e.uqtr.ca/6864/1/030518183.pdf.
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Parizot, Gérald. "Étude d'un procédé de fabrication de pièces en composite verre-époxyde réticulées par haute fréquence." Nancy 1, 1999. http://www.theses.fr/1999NAN10035.
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Ce travail est consacré à l'étude d'une installation permettant la réticulation de pièces en composite verre-époxyde par chauffage haute fréquence, destinées à l'industrie automobile. L'installation est instrumentée pour mesurer en temps réel la permittivité complexe du matériau, la puissance absorbée par matériau, le champ électromagnétique et la température en différents points de la pièce. Le procédé de réticulation est modélisé par un modèle de connaissance, dont les valeurs des paramètres ont été déterminées pour que les températures estimées suivent les températures mesurées. Les paramètres cinétiques, thermiques et diélectriques ont une signification physique. Ils peuvent être comparés aux informations caractéristiques du matériau, obtenues par ailleurs. Les pièces à réaliser sont disposées dans un applicateur coaxial, entre les plateaux d'une presse. Il est montré que le profil de tension appliqué aux pièces peut être ajusté pour compenser les variations d'épaisseur des pièces le long de leur longueur si on sait choisir convenablement la longueur d'onde de propagation, placer des impédances parallèles le long de l'applicateur à des endroits définis par le profil à obtenir et induire une répartition TEM pure du champ électromagnétique par une alimentation distribuée en 4 points. On a construit et justifié un schéma électrique équivalent de l'applicateur réel permettant de concevoir la connexion correcte entre le générateur et l'applicateur et on a montré qu'il y a lieu d'interpréter avec soin les mesures directes du champ électromagnétique que l'on peut faire avec une antenne insérée dans l'enceinte.
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Mazian, Brahim. "Approche intégrée du procédé de rouissage des fibres de chanvre : Vers une amélioration de la qualité des intrants pour la fabrication des matériaux biocomposites." Thesis, IMT Mines Alès, 2018. http://www.theses.fr/2018EMAL0006/document.
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Les réelles opportunités de croissance dont bénéficient les marchés liés à l'utilisation de fibres végétales en tant que renfort dans les matériaux composites sont intimement liées aux performances concurrentielles de ces fibres par rapport à celles de fibres de verre en particulier l’allégement, l’amortissement et l’isolation thermique. Dans l'industrie de la fibre de chanvre, le rouissage est le premier traitement appliqué aux plantes afin de faciliter la séparation des fibres de la partie ligneuse centrale de la tige. Ce traitement est actuellement réalisé de manière empirique en champ conduisant à l’obtention de fibres de qualité variable (couleur, morphologie, microstructure, composition biochimique, propriétés thermiques et mécaniques) ce qui constitue un frein à leur utilisation plus large dans des composites hautes performances. Par conséquent, la maîtrise du rouissage est primordiale. L’objectif de ce travail de thèse est de développer une approche globale de cette étape-clé de la production des fibres de chanvre en combinant à la fois l’étude du mécanisme biologique du rouissage, celle des caractéristiques intrinsèques des fibres et celle des émissions gazeuses et des odeurs associées à l’étape de rouissage. Différents items ont été particulièrement examinés :- L’influence de la durée du rouissage et de la période de récolte sur les caractéristiques intrinsèques des fibres de chanvre (couleur, morphologie, composition biochimique, microstructure, propriétés mécaniques, propriétés thermiques).- L’évolution des émissions de composés organiques volatils (COV) et de l'odeur lors du rouissage en champ.- La dynamique temporelle des densités de population des communautés bactériennes et fongiques pendant le rouissage- L'impact du rouissage en champ (climat méditerranéen) et du rouissage accéléré (conditions contrôlées en laboratoire) sur les propriétés microstructurales, thermiques et mécaniques d’un biocomposite polypropylène/fibre de chanvreThe natural fibres are increasingly used as reinforcements in polymer composites due to their challenging performances compared to conventional fibres in term of good specific mechanical properties, damping and thermal insulation. In the hemp industry, the retting is an upstream processing applied to the plants in order to facilitate the separation of fibres from the central woody part of the stem. This treatment is currently carried out in an empirical way in the fields that leads to a large variability in the hemp fibres instrinsic characteristics (color, morphology, biochemical composition, microstructure, thermal and mechanical properties) which limit their large use in high-performance composites. Therefore, controlling retting treatment is a crucial step. The aim of this thesis is to develop a global approach to this key step in the production of hemp fibers by combining the study of the biological mechanism of retting, the intrinsic characteristics of fibers and that of emissions volatile organic compounds and odors associated with the retting step. Different items were particularly examined:- The influence of retting duration and harvest period on the intrinsic characteristics of hemp fibers (color, morphology, biochemical composition, microstructure, mechanical and thermal properties).- The evolution of Volatile Organic Compounds (VOCs) and odors of hemp stems during field retting- Temporal dynamics of population densities of bacterial and fungal communities during retting- The impact of field retting (Mediterranean climate) and accelerated retting (controlled conditions in the laboratory) on the microstructural, thermal and mechanical properties of a polypropylene / hemp fibers biocomposite
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Griffin, Karl W. "Fabrication and characterisation of a hoop-reinforced, continuous silicon carbide fibre, titanium matrix composite produced by filament winding and hot isostatic pressing." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0014/MQ32398.pdf.
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Delaunay, Lionel. "Etude et réalisation d'un système de mesure du diamètre d'une fibre optique." Saint-Etienne, 1986. http://www.theses.fr/1986STET4004.
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Mesure du diamètre d'une fibre optique au cours de sa fabrication basée sur un principe physique interférométrique. Apres un calcul exact de l'intensité lumineuse diffusée par une fibre à saut d'indice éclairée perpendiculairement à son axe par un faisceau laser, on montre qu'il est possible d'interpréter le diagramme de rayonnement par l'interférence de deux rayons lumineux et on décrit deux méthodes de caractérisation du diamètre extérieur : l'une consiste à relier les déplacements des franges d'interférences aux variations du diamètre, l'autre consiste à compter le nombre de franges d'interférences dans un secteur angulaire donné au moyen d'une caméra à CCD et d'un microprocesseur
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Waris, Marc. "Mise en œuvre, instrumentation, validation et modélisation d’un système d’injection RTM pour la fabrication de structures composites de hautes performances." Thesis, Saint-Etienne, EMSE, 2012. http://www.theses.fr/2012EMSE0661/document.
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Les matériaux composites ont connu ces dernières années une forte croissance, croissance aujourd'hui renforcée par les nouvelles normes européenne visant à diminuer les émissions CO2 d'ici 2020. La réalisation de pièces complexes peut poser de nombreuses problématiques de fabrication comme la formation de zones sèches, ou la création de distorsions géométriques. Les origines de ces problématiques sont souvent liées à un manque de connaissance et de maîtrise des phases d'imprégnation des renforts et de cuisson du matériau. L'amélioration de la robustesse des procédés nécessite d'avoir une connaissance fine des phénomènes physiques qui ont lieu lors de l'élaboration. Dans cette perspective, les procédés d'élaboration de matériaux composites ont été étudiés à travers la mise en place d'un démonstrateur de laboratoire dans le cadre du projet LCM Smart. Ce pilote d'injection a permis de valider des solutions d'instrumentation, à partir de capteurs innovants (OFS) développés en partenariat avec le laboratoire d'optique Hubert Curien.L'application de cette instrumentation dans le cadre du suivi du procédé RTM a démontré les capacités des OFS pour le suivi des caractéristiques physiques de la pièce (le front d'écoulement, la température, les déformations résiduelles et le degré de cuisson). La comparaison des caractéristiques mesurées avec des simulations numériques effectuées en collaboration avec ESI, a montré une bonne corrélation.Enfin, l'instrumentation a permis de mettre en évidence l’intérêt d’un outillage composite en HexTool pour la réduction des contraintes résiduelles liées à l'interaction outil/pièceA significant growth in production and consumption of composite materials can be seen recently; growth reinforced by the new European standards, aimed at reducing CO2 emissions by the year 2020.The producing of complex parts can cause many difficulties for manufacturing because of their geometries and / or their constituents (using of various materials). For example, dry zones or geometric distortion formation. The origins of these difficulties are often related to a lack of knowledge and control of the reinforcement's impregnation phases and material curing.Improving the robustness of the processes demands a detailed knowledge of physical phenomena that occur during the producing. For this, we studied the composite materials production through the implementation of a laboratory demonstrator in the project LCM Smart. This pilot injection was used to validate instrumentation solutions, from innovative sensors (OFS) developed in partnership with the optical laboratory Hubert Curien. The application of this instrumentation in the context of RTM process monitoring in the development of simple parts has demonstrated the capabilities of OFS to control physical characteristics of the part (the flow front, temperature, residual strain and curing degree). The comparison of the measured characteristics with numerical simulations carried out in collaboration with ESI showed a good correlation.Finally, instrumentation has demonstrated the capacity of composite tool made by HexTool to minimize the residual stresses due to the tool/part interaction