Tesi sul tema "Fiber"
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1
MURA, EMANUELE. "PHOPSHATE OPTICAL FIBERS FOR IR FIBER LASERS". Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2544536.
Testo completo
2
Paye, Corey. "An Analysis of W-fibers and W-type Fiber Polarizers". Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32474.
Testo completoAbstract (sommario):
Optical fibers provide the means for transmitting large amounts of data from one
place to another and are used in high precision sensors. It is important to have a good
understanding of the fundamental properties of these devices to continue to improve their
applications.
A specially type of optical fiber known as a W-fiber has some desirable properties
and unique characteristics not found in matched-cladding fibers. A properly designed W-
fiber supports a fundamental mode with a finite cutoff wavelength. At discrete
wavelengths longer than cutoff, the fundamental mode experiences large amounts of loss.
The mechanism for loss can be described in terms of interaction between the fiberâ ¢s
supermodes and the lossy interface at the fiberâ ¢s surface. Experiments and computer
simulations support this model of W-fibers.
The property of a finite cutoff wavelength can be used to develop various fiber
devices. Under consideration here is the fiber polarizer. The fiber polarizer produces an
output that is linearly polarized along one of the fiberâ ¢s principal axes. Some of the
polarizer properties can be understood from the study of W-fibers.Master of Science
3
Polley, Arup. "High performance multimode fiber systems a comprehensive approach /". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31699.
Testo completoAbstract (sommario):
Thesis (Ph.D)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009.Committee Chair: Ralph, Stephen; Committee Member: Barry, John; Committee Member: Chang, G. K.; Committee Member: Cressler, John D.; Committee Member: Trebino. Part of the SMARTech Electronic Thesis and Dissertation Collection.
4
Rugeland, Patrik. "Applications of monolithic fiber interferometers and actively controlled fibers". Doctoral thesis, KTH, Laserfysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-118750.
Testo completoAbstract (sommario):
The objective of this thesis was to develop applications of monolithic fiber devices and actively controlled fibers. A special twin-core fiber known as a ‘Gemini’ fiber was used to construct equal arm-length fiber interferometers, impervious to temperature and mechanical perturbations. A broadband add/drop multiplexer was constructed by inscribing fiber Bragg gratings in the arms of a Gemini Mach-Zehnder interferometer. A broadband interferometric nanosecond switch was constructed from a micro-structured Gemini fiber with incorporated metal electrodes. Additionally, a Michelson fiber interferometer was built from an asymmetric twin-core fiber and used as a high-temperature sensor. While the device could be readily used to measure temperatures below 300 °C, an annealing process was required to extend the range up to 700 °C. The work included development, construction and evaluation of the components along with numerical simulations to estimate their behaviors and to understand the underlying processes. The thesis also explored the use of electrically controlled fibers for filtering in the microwave domain. An ultra-narrow phase-shifted fiber Bragg grating inscribed in a fiber with internal electrodes was used as a scanning filter to measure modulation frequencies applied to an optical carrier. A similar grating was used inside a dual-wavelength fiber laser cavity, to generated tunable microwave beat frequencies. The studied monolithic fiber interferometers and actively controlled fibers provide excellent building blocks in such varied field as in microwave photonics, telecommunications, sensors, and high-speed switching, and will allow for further applications in the future.Syftet med denna avhandling var att utveckla tillämpningar av monolitiska fiber komponenter samt aktivt kontrollerbara fiber. En speciell tvillingkärnefiber, även kallad ’Geminifiber’ användes för att konstruera fiber interferometrar med identisk armlängd som ej påverkas av termiska och mekaniska variationer. En bredbanding utbytarmultiplexor konstruerades genom att skriva in fiber Bragg gitter inuti grenarna på en Gemini Mach-Zehnder interferometer. Geminifibrer med interna metallelektroder användes för att konstruera en bredbandig nanosekundsnabb interferometrisk fiberomkopplare. Därtill användes en tvillingkärnefiber som en hög-temperatursensor. Även om komponenten direkt kan användas upp till 300 °C, måste den värmebehandlas för att kunna användas upp till 700 °C. Arbetet har innefattat utveckling, konstruktion och utvärdering av komponenterna parallellt med numeriska simuleringar för att analysera deras beteenden samt få insikt om de underliggande fysikaliska processerna. Avhandlingen behandlar även tillämpningar av en elektriskt styrbar fiber för att filtrera radiofrekvenser. Ett ultrasmalt fasskiftat fiber Bragg gitter skrevs in i en fiber med interna elektroder och användes som ett svepande filter för att mäta modulationsfrekvensen på en optisk bärfrekvens. Ett liknande gitter användes inuti en laserkavitet för att generera två olika våglängder samtidigt. Dessa två våglängder användes sedan för att generera en svävningsfrekvens i mikrovågsbandet. De undersökta monolitiska fiberinterferometrarna och de aktivt styrbara fibrerna erbjuder en utmärkt byggsten inom så pass skiljda områden som Mikrovågsfotonik, Telekommunikation, Sensorer samt Höghastighets-omkopplare och bör kunna användas inom många olika tillämpningar i framtiden.
QC 20130226
5
Richmond, Eric William. "Birefringent single-arm fiber optic enthalpimeter for catalytic reaction monitoring". Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07282008-135248/.
Testo completo
6
Jollivet, Clemence. "Specialty Fiber Lasers and Novel Fiber Devices". Doctoral diss., University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6295.
Testo completoAbstract (sommario):
At the Dawn of the 21st century, the field of specialty optical fibers experienced a scientific revolution with the introduction of the stack-and-draw technique, a multi-steps and advanced fiber fabrication method, which enabled the creation of well-controlled micro-structured designs. Since then, an extremely wide variety of finely tuned fiber structures have been demonstrated including novel materials and novel designs.
As the complexity of the fiber design increased, highly-controlled fabrication processes became critical. To determine the ability of a novel fiber design to deliver light with properties tailored according to a specific application, several mode analysis techniques were reported, addressing the recurring needs for in-depth fiber characterization.
The first part of this dissertation details a novel experiment that was demonstrated to achieve modal decomposition with extended capabilities, reaching beyond the limits set by the existing mode analysis techniques. As a result, individual transverse modes carrying between ~0.01% and ~30% of the total light were resolved with unmatched accuracy. Furthermore, this approach was employed to decompose the light guided in Large-Mode Area (LMA) fiber, Photonic Crystal Fiber (PCF) and Leakage Channel Fiber (LCF). The single-mode performances were evaluated and compared. As a result, the suitability of each specialty fiber design to be implemented for power-scaling applications of fiber laser systems was experimentally determined.
The second part of this dissertation is dedicated to novel specialty fiber laser systems. First, challenges related to the monolithic integration of novel and complex specialty fiber designs in all-fiber systems were addressed. The poor design and size compatibility between specialty fibers and conventional fiber-based components limits their monolithic integration due to high coupling loss and unstable performances. Here, novel all-fiber Mode-Field Adapter (MFA) devices made of selected segments of Graded Index Multimode Fiber (GIMF) were implemented to mitigate the coupling losses between a LMA PCF and a conventional Single-Mode Fiber (SMF), presenting an initial 18-fold mode-field area mismatch. It was experimentally demonstrated that the overall transmission in the mode-matched fiber chain was increased by more than 11 dB (the MFA was a 250 ?m piece of 50 ?m core diameter GIMF). This approach was further employed to assemble monolithic fiber laser cavities combining an active LMA PCF and fiber Bragg gratings (FBG) in conventional SMF. It was demonstrated that intra-cavity mode-matching results in an efficient (60%) and narrow-linewidth (200 pm) laser emission at the FBG wavelength.
In the last section of this dissertation, monolithic Multi-Core Fiber (MCF) laser cavities were reported for the first time. Compared to existing MCF lasers, renown for high-brightness beam delivery after selection of the in-phase supermode, the present new generation of 7-coupled-cores Yb-doped fiber laser uses the gain from several supermodes simultaneously. In order to uncover mode competition mechanisms during amplification and the complex dynamics of multi-supermode lasing, novel diagnostic approaches were demonstrated. After characterizing the laser behavior, the first observations of self-mode-locking in linear MCF laser cavities were discovered.Ph.D.
Doctorate
Optics and Photonics
Optics and Photonics
Optics and Photonics
7
Horvath, A. Elisabet. "The effects of cellulosic fiber charges on polyelectrolyte adsorption and fiber-fiber interactions". Doctoral thesis, Stockholm : Department of Fibre and Polymer Technology, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4158.
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8
Kuhlmey, Boris T. "Theoretical and numerical investigation of the physics of microstructured optical fibres". Connect to full text, 2004. http://setis.library.usyd.edu.au/adt/public_html/adt-NU/public/adt-NU20040715.171105.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--School of Physics, Faculty of Science, University of Sydney, 2004. (In conjunction with: Université de Droit, d'Économie et des Sciences d'Aix-Marseille (Aix Marseille III)).Bibliography: leaves 196-204.
9
Snyder, Heidi Ghent. "Fiber type-specific desmin content in human single muscle fibers /". Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1253.pdf.
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10
Ghent, Heidi. "Fiber Type-specific Desmin Content in Human Single Muscle Fibers". BYU ScholarsArchive, 2006. https://scholarsarchive.byu.edu/etd/381.
Testo completoAbstract (sommario):
Contractile and cytoskeletal protein concentrations have been shown to differ on the basis of fiber type in whole muscle homogenates. The purpose of this study was to compare the content of the intermediate filament protein, desmin, between type I and type IIa single muscle fibers from a mixed muscle in human subjects. Biopsies were taken from the vastus lateralis of six recreationally active males. Approximately 150 single muscle fibers were dissected from each sample and analyzed using SDS-PAGE to determine myosin heavy chain (MHC) composition. Following identification, muscle fibers were pooled into two groups (MHC I and MHC IIa). Desmin and actin content within the pooled samples was determined via immunoblotting. On average, muscle samples were composed of 51 ± 7 % type I, 2 ± 1% type I/IIa, 27 ± 5% type IIa, 19 ± 4% type IIa/IIx and 1 ± 1% type IIx MHC single fibers. Desmin and actin contents were 40% and 34% higher in type I fibers compared to type IIa fibers, respectively (P < 0.05). However the desmin to actin ratio was similar between pooled type I and IIa single muscle fibers within the vastus lateralis. These data suggest that desmin and actin content is a function of muscle fiber type. These differences in cytoskeletal protein content may have implications for differences in contractile function and eccentric damage characteristics between fiber types.
11
Wern, Chien Wei. "Fiber and fiber-matrix interface effects on the orthogonal cutting of fiber reinforced plastics /". Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/7133.
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12
Hartley, William H. "High-Speed Imaging of Polymer Induced Fiber Flocculation". Thesis, Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14627.
Testo completoAbstract (sommario):
This study presents quantitative results on the effect on individual fiber length during fiber flocculation. Flocculation was induced by a cationic polyacrylamide (cPAM). A high speed camera recorded 25 second video clips. The videos were image-analyzed and the fiber length and the amount of fiber in each sample were measured. Prior to the flocculation process, fibers were fractionated into short and long fibers. Trials were conducted using the unfractionated fiber, short fiber, and long fiber. The short and long fibers were mixed in several trials to study the effect of fiber length. The concentration of cPAM was varied as well as the motor speed of the impeller (RPM). It was found that the average fiber length decreased more rapidly with increasing motor speed. Increasing the concentration of cPAM also led to a greater decrease in average fiber length. A key finding was that a plateau was reached where further increasing the amount of cPAM had no effect. Hence, fibers below a critical length resisted flocculation even if the chemical dose or shear was increased. This critical length was related to the initial length of the fiber.
13
Srinivas, K. T. "Axial strain effects on optical fiber mode patterns". Thesis, This resource online, 1987. http://scholar.lib.vt.edu/theses/available/etd-04122010-083554/.
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14
Ratu, Ricky Novry. "Development of polypropylene fiber as concrete reinforcing fiber". Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/57779.
Testo completoAbstract (sommario):
The objective of this research is to produce polypropylene fibers with improved interface bonding with a concrete matrix. The Laboratory Mixing Extruder paired with the Randcastle fiberline drawing device was used for producing fiber from polypropylene (PP) chips. A target diameter of 0.5 mm fiber was obtained from a 2-stage process in the production line. The effort to improve the fiber surface by applying aluminum oxide sol-gel coating was unsatisfactory due to the failure of the coating materials to adhere to the fiber. Incorporating silica fume (SF) powder in the fiber extrusion process enhanced fiber properties. Silica fume co-extruded PP (SFPP) fiber has different characteristics in appearance, flexibility and surface roughness. Most importantly, the co-extrusions produced significance improvements in surface characteristics. Silica fume particles caused significant changes in the surface roughness of the fiber and contributed to the improved bonding performance in a cement-based matrix. The inclusion of the extruded fibers in a concrete matrix also improved the flexural toughness. Additional testing was conducted to examine the performance of extruded fiber in preventing plastic shrinkage cracking. Fiber reinforced mortar containing RPP and SFPP fibers were evaluated. Based on total crack area reduction efficiency, and crack width reduction efficiency SFPP fibers performed better than RPP fibers. These results indicate that the objective of developing a concrete reinforcing fiber using laboratory equipment was successfully achieved. The inclusion of silica fume particles in the extrusion process significantly changed the properties of the fiber and therefore contributed to the performance of these extruded fibers in the concrete matrix.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
15
Fernberg, Patrik. "Fiber bridging concepts applied to short fiber composites". Licentiate thesis, Luleå tekniska universitet, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18743.
Testo completoAbstract (sommario):
Polymer composite materials are in wide-spread use in the transportation industry. In aerospace industry the use these materials are established while in automotive industry the interest is increasing. The attention of automotive industry is to a great deal focused on various kinds of molded composites such as glass mat reinforced thermoplastics (GMT) and sheet molding compound (SMC). Their interest is to a large extent driven by the possibility to manufacture components of complex geometry in a cost- efficient process with these materials. An increasing number of car and truck manufacturers are using SMC for external panels such as trunk covers, hoods, roofs and spoilers. A property of obvious importance for an external car- or truck-panel is its capacity to withstand impact. In this context, improved understanding of crack growth and toughening mechanisms of the material is of great interest. A major part of the work presented in this thesis is driven by an interest to increase the understanding of how material composition and microstructure of short fiber composites influence their overall fracture behaviour. In materials such as metals and unreinforced polymers, linear elastic fracture mechanics (LEFM) is widely used, often with great success, both in design and in development of new materials. Unfortunately, problems arise when LEFM is applied to short fiber composites. This is due to the large process zone that develops ahead of a crack in these materials. The fundamental assumption of LEFM, that the damage zone at the tip of the crack is small compared to crack length, is often violated in experiments. The presented thesis considers a different approach, in which the damage ahead of a crack tip is described by a bridging-law. By considering the bridging-law as the major failure property of the material, a coupling between mechanisms acting on a microscale and the macroscopic failure behaviour can be established. No such information can be obtained using a LEFM approach where the material behaviour is described in terms of a single value, the fracture toughness. Bridging-laws for three different short fiber composites are experimentally determined and presented in the first paper of the thesis. A matter of key importance for future work in this field is that there are methods available for experimental verification of the suggested fiber bridging approach. Optical strain field measurement methods are therefore very useful. The thesis contains a pilot study to evaluate the use of two recently developed optical methods , Stereoscopic Digital Speckle Photography (Stereo-DSP) and combined DSP-DSPI (Digital Speckle Pattern Interferometry), for measurements of fracture behaviour of notched short fiber composites. We found Stereo-DSP to be a versatile technique that can be used when knowledge of overall displacement fields is required. The combined technique can with advantage be used when detailed information about large deformation at small areas is of interest, e.g. the complex fiber bridging interaction at the crack tip of a short fiber composite. The last paper in the thesis presents a study where the influence of fiber surface treatment on transverse cracking in cross-ply laminates was investigated. In the case of tubes and pressure vessels, the formation of transverse cracks ultimately leads to leakage since cracks connect and form a path through the wall. In the presented study, our ambition was to investigate the influence of film former polymer on transverse cracking properties of cross-ply laminates.Both onset of transverse cracking and tendency for multiple crack development were strongly affected by the different film formers. The strong film former effect was proposed to be due to a combination of improved interfacial adhesion and the plasticizing effect from the film former on the interphase region. The thesis is composed by the following papers: Patrik Fernberg, Lars Berglund, Bridging law and toughness characterisation of CSM and SMC composite, to be submitted. Angelica Andersson, Patrik Fernberg, Mikael Sjödahl, Optical methods to study fracture of notched glass mat composites. Proceedings of the International Conference on trends in Optical Nondestructive Testing, Lugano, Switzerland, May 3-6, 2000 (in press). Patrik Fernberg, Lars Berglund, Effects of glass fiber size composition (film former type) on transverse cracking in cross-ply laminates. Accepted for publication in Composites, Part A.Godkänd; 2000; 20070318 (ysko)
16
Smith, Kevin H. "In-fiber Optical Devices Based on D-fiber". BYU ScholarsArchive, 2005. https://scholarsarchive.byu.edu/etd/291.
Testo completoAbstract (sommario):
This dissertation presents the fabrication and analysis of in-fiber devices based on elliptical core D-shaped optical fiber. Devices created inside optical fibers are attractive for a variety of reasons including low loss, high efficiency, self-alignment, light weight, multiplexibility, and resistance to electromagnetic interference. This work details how D-fiber can be used as a platform for a variety of devices and describes the creation and performance of two of these devices: an in-fiber polymer waveguide and a surface relief fiber Bragg grating. In D-fiber the core is very close to the flat side of the ‘D’ shape. This proximity allows access to the fields in the fiber core by removal of the cladding above the core. The D-fiber we use also has an elliptical core, allowing for the creation of polarimetric devices. This work describes two different etch processes using hydrofluoric acid (HF) to remove the fiber cladding and core. For the creation of devices in the fiber core, the core is partially removed and replaced with another material possessing the required optical properties. For devices which interact with the evanescent field, cladding removal is terminated before acid breaches the core. Etching fibers prepares them for use in the creation of in-fiber devices. Materials are placed into the groove left when the core of a fiber is partially removed to form a hybrid waveguide in which light is guided by both the leftover core and the inserted material. These in-fiber polymer waveguides have insertion loss less than 2 dB and can potentially be the basis for a number of electro-optic devices or sensors. A polarimetric temperature sensor demonstrates the feasibility of the core replacement method. This work also describes the creation of a surface relief fiber Bragg gratings (SR-FBGs) in the cladding above the core of the fiber. Because it is etched into the surface topography of the fiber, a SR-FBG can operate at much higher temperatures than a standard FBG, up to at least 1100 degrees Celsius. The performance of a SR-FBG is demonstrated in temperature sensing at high temperatures, and as a strain sensor.
17
Scott, David Edward. "Characterization of fibrillated polypropylene and recycled waste fiber reinforced concrete". Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/19543.
Testo completo
18
Washburn, Brian Richard. "Dispersion and nonlinearities associated with supercontinuum generation in microstructure fibers". Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/30964.
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19
Heisey, Cheryl L. "Adhesion of novel high performance polymers to carbon fibers : fiber surface treatment, characterization, and microbond single fiber pull-out test /". Diss., This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-02052007-081244/.
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20
Сад, Альона Юріївна. "Optical fiber". Thesis, Київський національний університет технологій та дизайну, 2017. https://er.knutd.edu.ua/handle/123456789/7391.
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Misner, Scottie. "Dietary Fiber". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2006. http://hdl.handle.net/10150/146440.
Testo completoAbstract (sommario):
2 pp.Even dietary fiber is not considered a nutrient, health professionals agree that most Americans don't get nearly enough in their diet. So, why is fiber important? what does fiber do? This article answers the questions regarding diet fiber by providing information on the practical aspects of fiber in the diet as well as food sources and their dietary fiber content.
22
Misner, Scottie, Evelyn Whitmer e Traci Armstrong Florian. "Dietary Fiber". College of Agriculture and Life Sciences, University of Arizona (Tucson, AZ), 2013. http://hdl.handle.net/10150/298146.
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Borodulina, Svetlana. "Micromechanics of Fiber Networks". Doctoral thesis, KTH, Hållfasthetslära (Inst.), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188481.
Testo completoAbstract (sommario):
The current trends in papermaking involve, but are not limited to, maintaining the dry strength of paper material at a reduced cost. Since any small changes in the process affect several factors at once, it is difficult to relate the exact impact of these changes promptly. Hence, the detailed models of the network level of a dry sheet have to be studied extensively in order to attain the infinitesimal changes in the final product. In Paper A, we have investigated a relation between micromechanical processes and the stress–strain curve of a dry fiber network during tensile loading. The impact of “non-traditional” bonding parameters, such as compliance of bonding regions, work of separation and the actual number of effective bonds, is discussed. In Paper B, we studied the impact of the chemical composition of the fiber cell wall, as well as its geometrical properties, on the fiber mechanical properties using the three-dimensional model of a fiber with helical orientation of microfibrils at a range of different microfibril angles (MFA). In order to accurately characterize the fiber and bond properties inside the network, via statistical distributions, microtomography studies on the handsheets have been carried out. This work is divided into two parts: Paper C, which describes the methods of data acquisition and Paper D, where we discuss the extracted data. Here, all measurements were performed at a fiber level, providing data on the fiber width distribution, width-to-height ratio of isotropically oriented fibers and contact density. In the last paper, we utilize data thus obtained in conjunction with fiber morphology data from Papers C and D to update the network generation algorithm in order to produce more realistic fiber networks. We also successfully verified the models with the help of experimental results from dry sheets tested under uniaxial tensile tests. We carry out numerical simulations on these networks to ascertain the influence of fiber and bond parameters on the network strength properties.QC 20160613
24
Robinson, Risa J. "Polarization modulation and splicing techniques for stressed birefringent fiber /". Online version of thesis, 1995. http://hdl.handle.net/1850/12228.
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Wang, Xiaozhen. "Characterization of Fiber Tapers for Fiber Devices and Sensors". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23330.
Testo completoAbstract (sommario):
Fiber tapers have attracted much attention and have been successfully employed in various applications, ranging from resonators, filters, interferometers to sensors. This thesis studies the properties of fiber tapers for the purpose of making tapered-based devices and sensors in aerospace related application where small size and light weight are critical. This thesis includes theoretical derivation and experimental verifications of distributed mode coupling in tapered single-mode fibers (SMFs) with high-resolution optical frequency-domain reflectometry (OFDR) technique. The studies are realized with OFDR through phase detection of a Mach-Zehnder interferometer (MZI), which measures local refractive index change relative to the reference arm. The wavelength shifts converted by the phase change give the group index differences between the fundamental mode and higher-order modes of fiber tapers. The energy re-distribution is observed in Rayleigh backscatter amplitude as a function of fiber length with a ~13µm resolution over the entire fiber taper, and group index difference between core and cladding modes is measured with a spatial resolution of ~2cm by using autocorrelation data processing. The thermal and mechanical properties of fiber tapers have also been characterized with OFDR. The cross-correlation wavelength shift is related to the refractive index change of the modes. It is shown that residual stress induced by the tapering process results in the inhomogeneous thermal property, which can be significantly reduced by an annealing treatment. A fiber taper with a waist diameter of ~6µm has a force sensitivity of ~620.83nm/N, ~500 times higher than that of SMF. Furthermore, polarization-preserving character of tapered polarization-maintaining fibers (PMFs) is evaluated by OFDR-based distributed birefringence along tapered PMFs. Three tapered-based micro-fiber devices have been used as effective mode selecting components to build narrow-linewidth tunable Erbium-doped fiber ring lasers. The fabrication is easy and at a low cost. 1) a tapered fiber tip forms multimode interference mechanism; 2) a two-taper MZI has been demonstrated by splitting/combining the fundamental mode and higher-order modes through fiber tapers and is tuned by bending one taper waist; 3) a novel tunable fiber Fabry-Perot filter, consisting of a hollow-core photonic bandgap fiber and a micro-fiber, is employed in the reflection mode.
26
Wang, Long. "Fiber Based Mode Locked Fiber Laser Using Kerr Effect". University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1454081445.
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27
Suzuki, Shigeru. "Optical Fiber Devices: Novel Fiber Lasers and Image Amplifier". Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/194910.
Testo completoAbstract (sommario):
Three fiber based optical devices: all phosphate glass fiber laser, single hybrid mode fiber laser, and fiber image amplifier, were investigated in this dissertation. Phosphate fiber Bragg grating (FBG) is desired to improve performance of recently developed high power single frequency lasers that were based on highly rare earth ion doped phosphate fibers because these lasers were fabricated with silica FBGs that have incompatible properties with standard phosphate glasses. Since standard phosphate glasses are not photosensitive, Ge-doped phosphate glasses were fabricated and their UV-photosensitivity was examined. A phosphate fiber that has Ge-doped core showed UV index changes more than ~1.1 × 10⁻³. An all-phosphate fiber laser was also demonstrated with the Ge-doped phosphate FBG. Single hybrid mode fiber laser that involves a large area mode in cavity formation was demonstrated. The fiber laser consists of an Er-doped active fiber and two FBGs. One FBG was a core-cladding mode converter, and the other FBG was a narrowband high reflector that selects the lasing wavelength and mode. This approach for designing a laser cavity provides a much larger mode area than conventional large-mode-area stepindex fibers, and is supposed to suitable for a high power fiber laser. Also this configuration allows us to make novel ring-like cavities and sensor devices that consist of higher mode of optical fibers. Image amplifier based on a highly rare earth ion doped phosphate fiber is a unique approach to overcome weakness of widely used image intensifiers that lose a lot of information in the image, such as spectral distribution, polarization, and phase. Image amplification with a 19-pixel optical image amplifier array based on high gain per unit length Yb³⁺-doped phosphate glass optical fiber was demonstrated. A 10-cm of the 19- pixel fiber image amplifier provides spatially uniform image amplification with gain of 30 dB/pixel or more. This image amplifier responds quickly to changes in the image position – with potential for GHz-level or higher frame rates. This unique approach for image amplification offers low noise, high gain, and wide field of view in a compact fiber-based device.
28
Kominsky, Daniel. "Development of Random Hole Optical Fiber and Crucible Technique Optical Fibers". Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28949.
Testo completoAbstract (sommario):
This dissertation reports the development of two new categories of optical fibers. These are the Random Hole Optical Fiber (RHOF) and the Crucible Technique Hybrid Fiber (CTF). The RHOF is a new class of microstructure fiber which possesses air holes which vary in diameter and location along the length of the fiber. Unlike all prior microstructure fibers, these RHOF do not have continuous air holes which extend throughout the fiber. The CTF is a method for incorporating glasses with vastly differing thermal properties into a single optical fiber. Each of these two classes of fiber brings a new set of optical characteristics into being. The RHOF exhibit many of the same guidance properties as the previously researched microstructure fibers, such as reduced mode counts in a large area core. CTF fibers show great promise for integrating core materials with extremely high levels of nonlinearity or gain. The initial goal of this work was to combine the two techniques to form a fiber with exceedingly high efficiency of nonlinear interactions.
Numerous methods have been endeavored in the attempt to achieve the fabrication of the RHOF. Some of the methods include the use of sol-gel glass, microbubbles, various silica powders, and silica powders with the incorporation of gas producing agents. Through careful balancing of the competing forces of surface tension and internal pressure it has been possible to produce an optical fiber which guides light successfully.
The optical loss of these fibers depends strongly on the geometrical arrangement of the air holes. Fibers with a higher number of smaller holes possess a markedly lower attenuation. RHOF also possess, to at least some degree the reduced mode number which has been extensively reported in the past for ordered hole fibers. Remarkably, the RHOF are also inherently pressure sensitive. When force is applied to an RHOF either isotropically, or on an axis perpendicular to the length of the fiber, a wavelength dependent loss is observed. This loss does not come with a corresponding response to temperature, rendering the RHOF highly anomalous in the area of fiber optic sensing techniques. Furthermore an ordered hole fiber was also tested to determine that this was not merely a hitherto undisclosed property of all microstructure fibers.
Crucible technique fibers have also been fabricated by constructing an extremely thick walled silica tube, which is sealed at the bottom. A piece of the glass that is desired for the core (such as Lead Indium Phosphate) is inserted into the hole which is in the center of the tube. The preform is then drawn on an fiber draw tower, resulting in a fiber with a core consisting of a material which has a coefficient of thermal expansion (CTE) or a melting temperature (Tm) which is not commonly compatible with those of silica.Ph. D.
29
Cassino, Christopher Daniel. "Detection of fiber fracture in Unidirectional Fiber Reinforced Composites using an In-Plane Fiber Optic Sensor". Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/32419.
Testo completoAbstract (sommario):
Fiber reinforced polymers (FRP) are an efficient and inexpensive method of repairing deteriorating infrastructure. FRP sheets can be applied to spalling bridge sections and columns to prevent further deterioration and increase stiffness. However, the effect of the environment on the long-term durability of FRP and how the various damage mechanisms initiate and develop are not known. Systems for structural health monitoring are being sought as a means of managing important components in transportation systems as assets in light of modern life cycle cost concepts. This study characterizes a fiber optic sensor for use in detecting acoustic emissions (AE) in FRP. The results of AE analysis (signal amplitude, frequency spectra, MARSE, and in-plane displacement) caused by simulated fiber fracture experiments and other types of mechanical loading in FRP test coupons are reported. The applications to the development of FRP structural health monitoring systems are also discussed.Master of Science
30
Hofmann, John. "Extension of the Method of Ellipses to Determining the Orientation of Long, Semi-flexible Fibers in Model 2- and 3-dimensional Geometries". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23921.
Testo completoAbstract (sommario):
The use of fiber-reinforced polymer composites formed via injection molding is of increasing interest due to their superior mechanical properties as compared to those of the polymer matrix alone. These mechanical properties, however, are strongly dependent on the fiber length and orientation distributions within a molded part. As such, there is a need to understand and model the orientation evolution of chopped fibers in flow in order to accurately simulate the final fiber orientation distribution within injection molded parts. As a result of this, accurate and reliable experimental measurement of fiber orientation is needed.
Within this research, the application and validity of the Method of Ellipses for determining the orientation of long, semi-flexible glass fibers within injection molded composites has been investigated. A fiber suspension with an average length of approximately 3.9 mm was the focus of this study and assumed to be representative of commercial distributions. A novel method to quantify fiber curvature was developed and utilized to show that flexibility in center-gated disc and the end-gated plaque samples was minimal on average for the selected fiber length distribution. Thus, it was determined that the Method of Ellipses was applicable when utilized to obtain reliable orientation data for the selected long glass fiber suspension and within the chosen geometries that exhibit 1-, 2-, and 3-dimensional velocity fields. However, a modified image analysis width was found to be necessary in regions of highly aligned fibers, due to the increase in ellipse size and the need to reduce the number of partial objects and thus minimize error. This allowed for a direct comparison of the experimental orientation behavior of short and long glass fibers within the center-gated disc and the end-gated plaque, as well as the effect of the orientation distributions on the global modulus of the part.Ph. D.
31
Lyyttkäinen, Katja Johanna. "Control of complex structural geometry in optical fibre drawing /". Connect to full text, 2004. http://setis.library.usyd.edu.au/adt/public_html/adt-NU/public/adt-NU20041011.120247.
Testo completo
32
Greaves, James David. "Numerical analysis of the outside vapor deposition process". Ohio : Ohio University, 1990. http://www.ohiolink.edu/etd/view.cgi?ohiou1183491109.
Testo completo
33
Lyytikäinen, Katja Johanna. "Control of complex structural geometry in optical fibre drawing". Connect to full text, 2004. http://hdl.handle.net/2123/597.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Sydney, 2004.Title from title screen (viewed 14 May 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Physics, Faculty of Science. Includes bibliographical references. Also available in print form.
34
Sangam, Ramyaa Ramesh. "Development of Polychromatic Laser Beacon Fiber Coupling System Based on Photonic Crystal Fibers". University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1386943018.
Testo completo
35
Joshi, Ninad Milind. "Study of the Effect of Unidirectional Carbon Fiber in Hybrid Glass Fiber / Carbon Fiber Sandwich Box Beams". University of Dayton / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1386188162.
Testo completo
36
Holmberg, Patrik. "Laser processing of Silica based glass". Doctoral thesis, KTH, Laserfysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173929.
Testo completoAbstract (sommario):
The main topic of this thesis work is photosensitivity and photo-structuring of optical fibers and bulk glass. Although research in the field of photosensitivity in glass and optical fibers has been ongoing for more than three decades, the underlying mechanisms are still not well understood. The objective was to gain a better understanding of the photo-response by studying photosensitivity from a thermodynamic perspective, as opposed to established research focusing on point defects and structural changes, and strain and stress in optical fibers. Optical fibers was mainly used for experimental studies for two reasons; first, photosensitivity in fibers is more pronounced and more elusive compared to its bulk counterpart, and secondly, fibers provide a simplified structure to study as they experimentally can be seen as one-dimensional.Initially, ablation experiments on bulk glass were performed using picosecond infrared pulses. With a design cross section of 40x40 μm, straight channels were fabricated on the top (facing incident light) and bottom side of the sample and the resulting geometries were analyzed. The results show a higher sensitivity to experimental parameters for bottom side ablation which was ascribed to material incubation effects. Moreover, on the top side, the resulting geometry has a V-shape, independent of experimental parameters, related to the numerical aperture of the focusing lens, which was ascribed to shadowing effects.After this work, the focus shifted towards optical fibers, UV-induced fiber Bragg gratings (FBGs) and thermal processing with conventional oven and with a CO2 laser as a source of radiant heat.First, a system for CO2 laser heating of optical fibers was constructed. For measuring the temperature of the processed fibers, a special type of FBG with high temperature stability, referred to as "Chemical Composition Grating" (CCG) was used. A thorough characterization and temperature calibration was performed and the results show the temperature dynamics with a temporal resolution of less than one millisecond. The temperature profile of the fiber and the laser beam intensity profile could be measured with a spatial resolution limited by the grating length and diameter of the fiber. Temperatures as high as ~ 1750 °C could be measured with corresponding heating and cooling rates of 10.500 K/s and 6.500 K/s.Subsequently, a thorough investigation of annealing and thermal regeneration of FBGs in standard telecommunication fibers was performed. The results show that thermal grating regeneration involves several mechanisms. For strong regeneration, an optimum annealing temperature near 900 C was found. Two different activation energies could be extracted from an Arrhenius of index modulation and Braggv iwavelength, having a crossing point also around 900 °C, indication a balance of two opposing mechanisms.Finally, the thermal dynamics and spectral evolution during formation of long period fiber gratings (LPGs) were investigated. The gratings were fabricated using the CO2 laser system by periodically grooving the fibers by thermal ablation. Transmission losses were reduced by carefully selecting the proper processing conditions. These parameters were identified by mapping groove depth and transmission loss to laser intensity and exposure time.Huvudtemana i denna avhandling är fotokänslighet och fotostrukturering av optiska fibrer och bulk glas. Trots att forskning inom fotokänslighet i glas och optiska fibrer har pågått under mer än tre decennier är de bakomliggande mekanismerna ännu inte klarlagda. Syftet var att få en bättre förståelse för fotoresponsen genom att studera fotokäsligheten ur ett termodynamiskt perspektiv, i motsats till etablerad forskning med fokus på punktdefekter och strukturförändringar, samt mekaniska spännings effekter i optiska fibrer. Optiska fibrer användes för flertalet av de experimentella studierna av två skäl; för det första är fotokänsligheten i fibrer större och dessutom vet man mindre om bakomliggande mekanismer jämfört med motsvarande bulk glas, och för det andra kan fibrer vara enklare att studera eftersom de experimentellt kan ses som en endimensionell struktur.Inledningsvis utfördes ablaherings experiment på bulk glas med en infraröd laser med pikosekund pulser. Raka kanaler med ett designtvärsnitt på 40x40 μm tillverkades på ovansidan (mot infallande ljus) och bottensidan av provet och de resulterande geometrierna analyserades. Resultaten visar en högre känslighet för variationer i experimentella parametrar vid ablahering på undersidan vilket kan förklaras av inkubations effekter i materialet. Dessutom är den resulterande geometrin på ovansidan V-formad, oavsett experimentella parametrar, vilket kunde relateras till den numeriska aperturen hos den fokuserande linsen, vilket förklaras av skuggningseffekter.Efter detta arbete flyttades fokus mot optiska fibrer, UV inducerade fiber Bragg gitter (FBG), och termisk bearbetning med konventionell ugn samt även med en CO2-laser som källa för strålningsvärme.Först konstruerades ett system för CO2-laservärmning av fibrer. För mätning av temperaturen hos bearbetade fibrer användes en speciell sorts FBG med hög temperaturstabilitet, kallade ”Chemical Composition Gratings” (CCG). En grundlig karaktärisering och temperaturkalibrering utfördes och temperaturdynamiken mättes med en tidsupplösning på under en millisekund. Temperaturprofilen i fibern, och laserns strålprofil, kunde mätas med en spatiell upplösning begränsad av gitterlängden och fiberns diameter. Temperaturer upp till ~1750 °C, vilket är högre än mjukpunktstemperaturen, kunde mätas med korresponderande uppvärmnings- och avsvalningshastighet på 10.500 K/s och 6.500 K/s.Därefter gjordes en omfattande undersökning av värmebearbetning och termisk regenerering av FBG:er i telekomfiber. Resultaten visar att termisk gitter-regenerering aktiveras av flera olika mekanismer. Värmebearbetning vid en temperatur omkring 900 °C resulterade i starka gitter efter en regenerering vid en temperatur på 1100 °C. Två olika aktiveringsenergier kunde extraheras från en Arrhenius plot avseende brytningsindexmodulation och Braggvåglängd, med en skärningspunkt tillika runt 900 °C, vilket indikerar en avvägning mellan två motverkande mekanismer vid denna temperatur.Slutligen undersöktes temperaturdynamiken och de spektrala egenskaperna under tillverkning av långperiodiga fibergitter (LPG). Gittren tillverkades med CO2-vi iilasersystemet genom att skapa en periodisk urgröpning medelst termisk ablahering. Transmissionsförluster kunde reduceras med noggrant valda processparametrar. Dessa parametrar identifierades genom mätningar av ablaherat djup och transmissionsförlust som funktion av laserintensitet och exponeringstid.
QC 20150924
37
Borton, Eric K. "Update and comparison of cumulative fiber exposure estimates for workers in a facility expanding Libby vermiculite". University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1335461760.
Testo completo
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Song, Jiawei, e Jiawei Song. "Nd-doped Fiber Lasers and Fiber Amplifiers at 9xx nm". Thesis, The University of Arizona, 2016. http://hdl.handle.net/10150/620827.
Testo completoAbstract (sommario):
The lasers operating in the wavelength range of 900 - 1000 nm have caused intense attention because they are in great demands for: 1. Highpower blue and deep UV laser generation 2. High power single-mode pump laser source 3. Light detection and Lidar , etc. And now, there are actually many different types of lasers can generate laser in this wavelength range. For example, Nd and Yb doped fiber laser, Nd and Yb doped glass and crystal lasers, OPO and SHG laser, etc. Among all this options, we decided to study the Nd-doped fiber laser for their outstanding advantages: 1. As fiber laser, it possess all the advantages of any fiber lasers have, such as: high power scalability, excellent beam quality, high spectral and intensity stability, super compactness, robustness and reliability. 2. Comparing to other rare-earth-ion, the Nd^3+ ions have a more broad emission wavelength range from 900-950 nm. My goals for doing this thesis research are:1.Experimentally and theoretically investigate Nd-doped fiber lasers and amplifiers at 9xx nm. 2. Develop 9xx nm single frequency fiber lasers and amplifiers. 3.Obtain directions for developing high power single-frequency Nd-doped fiber laser sources at 9xx nm. To achieve these goals, 1. Nd-doped fiber lasers at 934 nm were investigated. 2. Core-pumped and cladding-pumped Nd-doped fiber amplifiers are also investigated. 3. The simulation of the Nd-doped fiber amplifiers have been done.
39
Smulski, Stephen John. "Flexural behavior of a glass fiber reinforced wood fiber composite". Diss., Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/53596.
Testo completoAbstract (sommario):
The static and dynamic flexural properties of a wood fiber matrix internally reinforced with continuous glass fibers were investigated. When modelled as a sandwich composite, the static flexural modulus of elasticity (MOE) of glass fiber reinforced hardboard could be successfully predicted from the static flexural MOE of the wood fiber matrix, and the tensile MOE and effective volume fraction of the glass fiber reinforcement. Under the same assumption, the composite modulus of rupture (MOR) is a function of the reinforcement tensile MOE and effective volume fraction, and the matrix stress at failure. The composite MOR was predicted on this basis with limited success.
The static flexural modulus of elasticity, dynamic modulus of elasticity, and modulus of rupture of glass fiber reinforced hardboard increased with increasing effective reinforcement volume fraction. The logarithmic decrement of the composite decreased with increasing effective reinforcement volume fraction. Excellent linear correlation found among flexural properties determined in destructive static tests and nondestructive dynamic tests demonstrated the usefulness of dynamic test methods for flexural property evaluation.
The short-term flexural creep behavior of glass fiber reinforced hardboard was accurately described by a 4-element linear viscoelastic model. Excellent agreement existed between predicted and observed creep deflections based on nonlinear regression estimates of model parameters.Ph. D.
40
Li, Hongying. "Fiber tracking and fiber architecture description in cardiac DT-MRI". Thesis, Lyon, INSA, 2013. http://www.theses.fr/2013ISAL0125.
Testo completoAbstract (sommario):
La connaissance de l’architecture tridimensionnelle (3D) des fibres est cruciale dans la compréhension de la fonction du cœur humain. L’imagerie par résonance magnétique du tenseur de diffusion (IRM-DT) est une technique permettant de mesurer la diffusion des molécules d’eau dans des tissus humains, et donc d’étudier de manière non-invasive l’architecture 3D des fibres du cœur humain. Dans l’IRM-TD cardiaque, la tractographie des fibres est essentielle pour représenter et visualiser l’architecture des fibres, mais souvent utilisée qualitativement comme une dernière étape qui consiste à visualiser sur l’écran l’architecture myocardique obtenue à partir des données IRM-TD. Cependant, cette visualisation qualitative n’est pas suffisante pour décrire de manière objective et complète l’architecture des fibres. L’objectif de cette thèse est de développer de nouvelles approches pour la tractographie et pour la description quantitative de l’architecture des fibres cardiaques du cœur humain en IRM-TD cardiaque. Les travaux de cette thèse se focalisent sur trois axes. Le premier est le développement d’un algorithme de tractographie probabiliste, qui prend en compte la corrélation spatiale des fibres pendant le suivi des fibres myocardiques. Les résultats expérimentaux montrent que la méthode proposée est robuste au bruit. Les fibres produites sont plus régulières et plus lisses, et la configuration des fibres cardiaques est plus facile à observer. Le second axe concerne une nouvelle notion de dépliement de fibres pour décrire les fibres du cœur humain, qui sont souvent complexes dans l’espace 3D. L’idée est d’analyser cette architecture 3D dans un espace réduit à deux dimensions (2D), en utilisant une technique d’apprentissage de variété. L’approche de dépliement proposée permet la description quantitative de l’architecture 3D de fibres cardiaques dans un plan 2D. Les résultats montrent qu’il est beaucoup plus facile d’observer et d’étudier les caractéristiques des fibres cardiaques après les avoir dépliées, et qu’il semble exister des formes de fibres caractéristiques du cœur humain. Le dernier axe consiste en la fusion de fibres, qui est obtenue en moyennant les fibres selon une grille. Cette approche fournit des architectures de fibres simplifiée à différentes échelles, et permet de mieux mettre en évidence la configuration des fibres cardiaquesIt is important to study the cardiac fiber architecture in order to understand the heart function. Diffusion tensor MRI (DT-MRI) is the only noninvasive technique that allows studying cardiac fiber architecture in vivo. Tractography is essential in representing and visualizing cardiac fiber architecture in DT-MRI, but is often employed qualitatively. The motivation of this thesis is to develop technique for studying the cardiac fiber architecture from the fiber tracts provided by the tractography process in cardiac DT-MRI. Our goal is to develop tractography algorithm and approaches for the quantitative description of cardiac fiber architecture. My work is composed of three main axis. The first is the development of a probabilistic tractography algorithm, which takes fiber spatial correlation into accounts in tracing fibers. Experimental results show that the proposed method is meaningfully more robust to noise than the streamlining method, and produces more regular and smoother fibers, which enables cardiac fiber configurations to be more clearly observed. The second concerns a new framework, namely cardiac fiber unfolding, which is an isometric mapping. Our fiber unfolding framework allows the quantitative description of three dimensional cardiac fiber architecture in a two dimensional plan. Our experimental results show that fiber tract pattern can be observed much easier by unfolding them in a plane, and several cardiac fiber patterns were found. The last axis consists in merging fibers, which is achieved by averaging fibers according to a grid. This fiber merging approach provide simplified fiber architecture at different scale as output that highlights the cardiac fiber configuration
41
Fierling, Yannick P. H. "Analysis of fiber-reinforced composite plates utilizing curvilinear fiber trajectories". Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-01312009-063412/.
Testo completo
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Derrington, Dolores Cormack. "Overview of fiber optics technology: industrial and military". Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43896.
Testo completoAbstract (sommario):
Fiber optics technology is being used in many applications, both in
the military world and in the industrial world. A broad overview of
this technology is provided, including a discussion of the fundamentals
of fiber operation and component characteristics.
Applications of fiber optics in both military and industrial
communities is addressed, identifying specific examples in both cases.
In addition, market projections and technology trends are discussed for
both the military and industrial communities.Master of Science
43
Lee, Shiao-Chiu. "Axial offset effects upon optical fiber sensor and splice performance". Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/91128.
Testo completoAbstract (sommario):
A kind of intensity modulated fiber sensor utilizing axial offset parameter is proposed. The theoretical analysis and experimental characteristics of this sensor are described.
All the theoretical results derived in this thesis are based on assuming a uniform power distribution in the fibers. An expression of coupling efficiency of central dipped parabolic graded index fibers due to axial offset is derived. The results show less sensitivity to axial offset for the central dipped fibers than for the parabolic profile fibers without a dip. Expressions of coupling efficiency of graded index fibers due to axial offset for several different values of a are also derived. The results show that sensitivity increases as the value of a decreases. A general expression of coupling efficiency which is valid for small values of axial offset is derived. This expression exhibits a linear relationship between coupling efficiency and small axial offset.
Coupling efficiencies versus fiber end separation and axial offset of step index fibers have been measured. The measurements show that coupling efficiency is much more sensitive to axial offset than end separation. A simple construction of the axial offset fiber sensor is described. An approximate linear relationship between the output power and the mechanical loading has been obtained for this sensor. Several ways of increasing the sensitivity of this sensor are discussed.M.S.
44
Myrén, Niklas. "Poled fiber devices". Doctoral thesis, KTH, Physics, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-262.
Testo completoAbstract (sommario):
The topic of this thesis is the development of devices for telecom applications based on poled optical fibers. The focus is on a specific function, optical switching/modulation.
Some of the most important results are summarized below. Optical switching at telecom wavelengths (1.55 μm) is demonstrated in an all-fiber switch based on a fiber with internal electrodes. The fiber is made electro-optically active with a thermal poling process in which a strong electric field is recorded in the glass at a temperature of 255 °C. After poling, the fiber is put in one arm of a Mach-Zehnder interferometer and by applying a voltage across the two electrodes the refractive index is modulated and the optical signal switched from one output port to the other. A switching voltage of 190 V at 1550 nm was achieved, which to the best of our knowledge is the lowest value reported. By carefully matching the lengths of the fibers in the two arms of the interferometer the optical bandwidth could be made as large as 20 nm. The extinction ratio, determined by the power ratio in the two arms, was 30 dB and the highest modulation frequency was 30 MHz. Poled fibers were packaged to increase the thermal and mechanical stability and to make handling easier. 40 Gb/s transmission test through the device showed no bit-error-rate performance degradation. Protection switching of a 10 Gb/s signal is also demonstrated.
The depletion region in a poled fiber was found to be wedge-shaped and very wide, 13 μm and completely overlapped with the core. In a time-resolved poling experiment the recorded electric field was measured. The sign of the field changed after ~20 min, when the depletion region passed through the core, which led to the conclusion that an electric field is present also outside of the depletion region.
A ring laser was constructed with an erbium doped fiber as the gain medium. A fiber modulator was placed inside the cavity and when a small RF signal, with a frequency matched to the cavity ground frequency, was applied to the modulator the laser was modelocked. The output pulse train contained pulses of sub ns duration and is the first demonstration of mode-locking using poled fibers.
A sampled grating with 16 channels spaced by 50 GHz was inserted into the cavity. The fiber modulator had optical bandwidth of 7 nm with center wavelength that depends on the applied voltage. By applying of 10 – 210 V to the modulator it was possible to tune the laser to 11 of the 16 channels for a total tuning range of over 4 nm.
A scheme to deposit 1 μm thin silver electrodes inside the holes of an optical fiber is demonstrated together with a new method of creating periodic electrodes by periodically ablating the silver film electrodes. The periodic electrodes are used to create a quasi-phase matched (QPM) nonlinearity in a fibers which is showed in a proof of principle experiment.
45
Myrén, Niklas. "Poled fiber devices /". Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-262.
Testo completo
46
Bock, Katherine J. "Femtosecond Fiber Lasers". Thèse, Université d'Ottawa / University of Ottawa, 2012. http://hdl.handle.net/10393/23391.
Testo completoAbstract (sommario):
This thesis focuses on research I have done on ytterbium-doped femtosecond fiber lasers. These lasers operate in the near infrared region, lasing at 1030 nm. This wavelength is particularly important in biomedical applications, which includes but is not limited to confocal microscopy and ablation for surgical incisions. Furthermore, fiber lasers are advantageous compared to solid state lasers in terms of their cost, form factor, and ease of use. Solid state lasers still dominate the market due to their comparatively high energy pulses. High energy pulse generation in fiber lasers is hindered by either optical wave breaking or by multipulsing. One of the main challenges for fiber lasers is to overcome these limitations to achieve high energy pulses. The motivation for the work done in this thesis is increasing the output pulse peak power and energy. The main idea of the work is that decreasing the nonlinearity that acts on the pulse inside the cavity will prevent optical wave breaking, and thus will generate higher energy pulses. By increasing the output energy, ytterbium-doped femtosecond fiber lasers can be competitive with solid state lasers which are used commonly in research. Although fiber lasers tend to lack the wavelength tuning ability of solid state lasers, many biomedical applications take advantage of the 1030 µm central wavelength of ytterbium-doped fiber lasers, so the major limiting factor of fiber lasers in this field is simply the output power. By increasing the output energy without resorting to external amplification, the cavity is optimized and cost can remain low and economical. During verification of the main idea, the cavity was examined for possible back-reflections and for components with narrow spectral bandwidths which may have contributed to the presence of multipulsing. Distinct cases of multipulsing, bound pulse and harmonic mode-locking, were observed and recorded as they may be of more interest in the future. The third-order dispersion contribution from the diffraction gratings inside the laser cavity was studied, as it was also considered to be an energy-limiting factor. No significant effect was found as a result of third-order dispersion; however, a region of operation was observed where two different pulse regimes were found at the same values of net cavity group velocity dispersion. Results verify the main idea and indicate that a long length of low-doped gain fiber is preferable to a shorter, more highly doped one. The low-doped fiber in an otherwise equivalent cavity allows the nonlinear phase shift to grow at a slower rate, which results in the pulse achieving a higher peak power before reaching the nonlinear phase shift threshold at which optical wave breaking occurs. For a range of net cavity group velocity dispersion values, the final result is that the low doped fiber generates pulses of approximately twice the value of energy of the highly-doped gain fiber. Two techniques of mode-locking cavities were investigated to achieve this result. The first cavity used NPE mode-locking which masked the results, and the second used a SESAM for mode-locking which gave clear results supporting the hypothesis.
47
Lestoquoy, Guillaume. "Multimaterial fiber electronics". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87929.
Testo completoAbstract (sommario):
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 119-129).
As the number of materials that are thermally-drawable into fibers is rapidly expending, numerous new multimaterial fiber architectures can be envisioned and fabricated. High-melting temperature metals, compound materials, composite, conductive or ferroelectric polymers: the broad diversity of these materials' nature and properties, combined with various post-fabrication treatments recently developed (poling, annealing, injection, coating, capillary breakup), enable the making of novel in-fiber, stand-alone-fiber and fiber-array devices. In this thesis, we demonstrate a wide variety of novel multimaterial fiber capabilities at all these levels, focusing specifically on new electronic functions. First, the implementation of conductive polymer as in-fiber current buses is shown to enable distributed light sensing and modulation along a single fiber, by inducing transmission-line effects in d.c. and a.c. operation. Next, the design and operation of a photosensing fiber specially treated to detect explosives is presented, and the sensitivity of this fiber device is shown to meet state-of-the-art industry standards. A novel large-interface-area design for dielectric fibers is then presented, which enables both energy storage in flexible fiber capacitors as well as enhanced acoustic transduction in piezoelectric fibers. The flexibility as well as the assembly into arrays of the latter are shown to enable the shaping of a pressure field in all three dimensions of space. Finally, a novel thermal-gradient capillary breakup process for silica-based fibers is shown, enabling the fabrication of silicon-in-silica micro spheres and rectifying devices. Taken as a whole, these new capabilities greatly expand the breadth of functionality of multimaterial fibers, further paving the way towards highly multifunctional, wholly integrated electronic fiber devices and fabrics that can collect, store and transduce energy in all of its forms.
by Guillaume Lestoquoy.
Ph. D.
48
Oblapenko, B. S. "Fiber optic cabling". Thesis, Сумський державний університет, 2012. http://essuir.sumdu.edu.ua/handle/123456789/28545.
Testo completo
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Battiato, James Michael 1966. "Fiber Bragg gratings". Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288905.
Testo completoAbstract (sommario):
The properties of fiber Bragg gratings are investigated theoretically and experimentally. The effects of experimental parameters on grating characteristics are modeled for both uniform and non-uniform gratings. Particular emphasis is placed on the formation of fiber Bragg gratings tilted at 45 degrees with respect to the fiber axis in single mode fibers. In this case, light is coupled out of the fiber in a surface normal manner. Several fabrication methods for producing tilted fiber gratings are explored and characterized. The most efficient gratings are obtained with a prism coupling technique. Experimental tilted grating performance is shown to be in good agreement with the predictions of a two-dimensional coupled mode theory. Fiber gratings are also used to demonstrate an Er/Nd co-doped fiber laser. This dual wavelength laser is formed with a common cavity and common gain medium.
50
Jin, Chuhang. "Microstructured Terahertz Fiber". Thesis, KTH, Tillämpad fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-265667.
Testo completo