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Dissertations / Theses on the topic 'Optical fibers'
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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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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/.
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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.
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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.
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Kominsky, Daniel. "Development of Random Hole Optical Fiber and Crucible Technique Optical Fibers." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/28949.
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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.
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Polley, Arup. "High performance multimode fiber systems a comprehensive approach /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/31699.
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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.
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Hao, Miin-Jong. "Performance evaluation of practival FSK, CPFSK, and ASK detection schemes for coherent optical fiber communication systems." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/15686.
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Paye, Corey. "An Analysis of W-fibers and W-type Fiber Polarizers." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/32474.
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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
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MURA, EMANUELE. "PHOPSHATE OPTICAL FIBERS FOR IR FIBER LASERS." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2544536.
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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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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.
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Lyytikäinen, Katja Johanna. "Control of complex structural geometry in optical fibre drawing." Connect to full text, 2004. http://hdl.handle.net/2123/597.
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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.
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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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Santos, Eliane Moura dos. "Processos relacionados a inserção de fluidos para sensoriamento com fibras de cristal fotônico." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/278251.
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Orientadores: Luiz Carlos Barbosa, Cristiano Monteiro de Barros CordeiroDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: Este trabalho apresenta estudos de como inserir fluidos (líquidos e gases) em fibras ópticas microestruturadas, especialmente fibras de cristal fotônico, também conhecidas como PCF¿s (do inglês Photonic Crystal Fibers). Estas fibras possuem buracos de ar que percorrem todo seu comprimento. Elas podem ser divididas em dois grandes grupos: as de núcleo sólido que guiam luz por reflexão interna total e as de núcleo oco que guiam luz por um mecanismo conhecido como photonic bandgap. Ambos os tipos de fibras permitem várias aplicações em áreas como óptica e fotônica e nos dedicamos aqui à área de sensoriamento a fibra. Nesta área, usamos os microburacos para inserir fluido e dessa maneira manipular as propriedades de guiamento (em fibras de núcleo líquido), deixar a fibra mais sensível a algum parâmetro externo ou para sensoriar o fluido em questão. Nos três casos, precisamos estudar os processos de preenchimentos de fibras microestruturadas. Para este fim, estudamos e desenvolvemos maneiras de inserir fluidos em fibras de núcleos sólidos ou ocos. Usando preenchimento seletivo, produzimos fibras com núcleo líquido, criando uma região de alta interação entre luz e material. Neste trabalho, estudamos diferentes técnicas de preenchimento. A primeira, para fibras de núcleo líquido, é um preenchimento seletivo que pode ser feito usando uma máquina de emendas (splicer) ou um polímero para bloquear os microburacos. O outro consiste em manter as pontas das fibras livres (para medidas ópticas) enquanto o preenchimento é feito. Por fim, usamos o conhecimento desses processos em aplicações como sensoriamento de fluidos ou parâmetros externos e manipulação de propriedades de guiamento da luz
Abstract: This work presents studies of how to insert fluids (liquid and gas) into microstructured optical fibers, especially photonic crystal fibers, also known as PCF¿s. These optical fibers possess air holes that run along its entire length. They can be divided into two major groups: solid core fibers that guide light by total internal reflection and hollow core fibers that guide light by photonic bandgap. Both types of fibers allow several applications in areas such as optics and photonics and we dedicated this work to the fiber-sensing field. In this area we use the micro holes to insert fluids and in this way to manipulate the guidance properties in liquid core fibers, to leave the fiber more sensitive to some external parameter or to sensing the fluid. In these three cases we need to study the filling procedures in microstructured fibers. For this purpose, we studied and developed ways of inserting fluids in hollow and solid core fibers. We produced liquid core fibers, creating a high light-material overlap, using a selective filling technique. In this work we studied different filling techniques. The first one, for liquid core fibers, is a selective filling, which can be done by using a splicer machine or a polymer to block the fiber micro holes. The last one consists of keeping the fiber tips free (for optical measurements) while the filling is done. And finally we used the filling process knowledge in applications like sensing of fluids or external parameters and manipulation of guidance properties
Mestrado
Física Geral
Mestre em Física
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Haakestad, Magnus W. "Optical fibers with periodic structures." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, 2006. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1494.
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This thesis concerns some experimental and theoretical issues in fiber optics. In particular, properties and devices based on photonic crystal fibers (PCFs) are investigated.
The work can be grouped into three parts. In the first part we use sound to control light in PCFs. The lowest order flexural acoustic mode of various PCFs is excited using an acoustic horn. The acoustic wave acts as a traveling long-period grating. This is utilized to couple light from the lowest order to the first higher order optical modes of the PCFs. Factors affecting the acoustooptic coupling bandwidth are also investigated. In particular, the effect of axial variations in acoustooptic phase-mismatch coefficient are studied.
In the second part of the thesis we use an electric field to control transmission properties of PCFs. Tunable photonic bandgap guidance is obtained by filling the holes of an initially index-guiding PCF with a nematic liquid crystal and applying an electric field. The electric field introduces a polarization-dependent change of transmission properties above a certain threshold field. By turning the applied field on/off, an electrically tunable optical switch is demonstrated.
The third part consists of two theoretical works. In the first work, we use relativistic causality, i.e. that signals cannot propagate faster than the vacuum velocity of light, to show that Kramers-Kronig relations exist for waveguides, even when material absorption is negligible in the frequency range of interest. It turns out that evanescent modes enter into the Kramers-Kronig relations as an effective loss term. The Kramers-Kronig relations are particularly simple in weakly guiding waveguides as the evanescent modes of these waveguides can be approximated by the evanescent modes of free space. In the second work we investigate dispersion properties of planar Bragg waveguides with advanced cladding structures. It is pointed out that Bragg waveguides with chirped claddings do not give dispersion characteristics significantly different from Bragg waveguides with periodic claddings.
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Boivin, Luc. "Squeezing in optical fibers." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38373.
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Cholst, Beth (Beth Ellen). "Elastic stretchable optical fibers." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/105710.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 23-24).
The utilization of soft materials in the design of optical systems provides opportunities for imparting these optical systems with completely unprecedented properties. This will enhance performance of systems, such as optical fibers, and enable new application scenarios. Here, we report the design, manufacture and characterization of elastic stretchable optical fibers. Analogous to conventional optical fibers, the elastic fibers consist of a high index core, made from a polystyrene-polyisoprene triblock copolymer, and a low refractive index cladding, formed by a fluorinated thermoplastic elastomer. The fibers are manufactured by co-extrusion of their constituent materials. They can be stretched to 300% strain repeatedly. Axial deformation of the fibers results in a variation of their light guiding properties. The fibers' attenuation coefficient was determined to be 0.021 ± 0.003 dB/mm, which is 2 orders of magnitude higher than for standard optical glass fibers. The high attenuation coefficient is likely due to scattering of light by air inclusions incorporated during manufacturing at the core-cladding interface. The fibers elastic modulus is 960 ± 280 kPA and their yield strength lies in the range of 2150 ± 480 kPA. The variation in intensity of guided light as a function of strain applied axially to the fibers was measured with a customized optical setup. Our experiments show that elastic optical fibers have properties that make them desirable as mechanical sensors and components in a range of other applications, provided current manufacturing shortcomings are addressed. The fibers could be used for light delivery to individual pixels of flexible deformable displays. They could be incorporated into clothing for delivery of light for display purposes or textile-integrated photonic circuits to create functional textiles. Because the fibers can stretch, the textiles or displays will be able to undergo deformation without damage or loss in performance.
by Beth Cholst.
S.B.
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Osório, Jonas Henrique 1989. "Specialty optical fibers for sensing = Fibras ópticas especiais para sensoriamento." [s.n.], 2017. http://repositorio.unicamp.br/jspui/handle/REPOSIP/330348.
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Orientador: Cristiano Monteiro de Barros CordeiroTese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
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Resumo: Nesta tese, fibras ópticas especiais são estudadas para fins de sensoriamento. Primei-ramente, propomos a estrutura denominada fibra capilar com núcleo embutido (embedded-core capillary fibers) para realização de sensoriamento de pressão. Estudos numéricos e analíticos foram realizados e mostraram que altas sensibilidades a variações de pressão poderiam ser al-cançadas com esta estrutura simplificada, que consiste de um capilar dotado de um núcleo, dopado com germânio, em sua parede. Experimentos permitiram medir uma sensibilidade de (1.04 ± 0.01) nm/bar, que é um valor alto quando comparado a outros sensores de pressão ba-seados em fibras microestruturadas. Ademais, estudamos fibras do tipo surface-core, que são fibras cujos núcleos são colocados na superfície externa da fibra. Nesta abordagem, redes de Bragg foram utilizadas para obter sensores de índice de refração ¿ fazendo-se uso da interação entre o campo evanescente do modo guiado no núcleo e o ambiente externo à fibra ¿ e de cur-vatura ¿ ao se explorar o fato de que, nestas fibras, o núcleo se encontra fora do centro geomé-trico da mesma. As sensibilidades a variações de índice de refração e curvatura medidas, 40 nm/RIU em torno de 1.41 e 202 pm/m-1 comparam-se bem a outros sensores baseados em redes de Bragg. Outrossim, fibras capilares poliméricas foram investigadas como sensores de temperatura e pressão. Para a descrição do sensor de temperatura, usou-se um modelo analítico para simular o espectro de transmissão dos capilares e a sua dependência com as variações de temperatura. No que tange à aplicação de sensoriamento de pressão, variações nas espessuras dos capilares devido à ação da pressão foram calculadas e relacionadas à sensibilidade da me-dida de monitoramento. Nestas duas aplicações, realizações experimentais também são repor-tadas. Finalmente, oportunidades adicionais de sensoriamento ao se utilizar fibras ópticas es-peciais são apresentadas, a saber, um sensor de pressão para dois ambientes baseados em fibras de cristal fotônico, um sensor de três parâmetros baseado em redes de Bragg, fibras afinadas e interferência multimodal, um sensor de nível de líquido baseado em redes de Bragg e interfe-rência multimodal e um sensor de temperatura baseado em fibras embedded-core preenchidas com índio. Os resultados aqui reportados demonstram o potencial das fibras ópticas em forne-cerem plataformas de sensoriamento para alcançar medidas de diferentes tipos de parâmetros com alta sensibilidade e resolução adequada
Abstract: In this thesis, specialty optical fibers for sensing applications are investigating. Firstly, we propose the embedded-core capillary fiber structure for acting as a pressure sensor. Analyt-ical and numerical studies were performed and showed that high pressure sensitivity could be achieved with this simplified fiber structure, which consists of a capillary structure with a germanium-doped core placed within the capillary wall. Experiments allowed measuring a sensitivity of (1.04 ± 0.01) nm/bar, which is high when compared to other microstructured optical fiber-based pressure sensors. Moreover, we studied the so-called surface-core optical fibers, which are fibers whose cores are placed at the external boundary of the fiber. In this approach, Bragg gratings were used to obtain refractive index ¿ making use of the interaction between the guided mode evanescent field and the external medium ¿ and directional curva-ture sensors ¿ by exploring the off-center core position. The measured refractive index and the curvature sensitivities, respectively 40 nm/RIU around 1.41 and 202 pm/m-1, compares well to other fiber Bragg grating-based sensors. Additionally, antiresonant polymer capillary fibers were investigated as temperature and pressure sensors. For the temperature sensing descrip-tion, one used an analytical model to simulate the transmission spectra of such fibers and the dependence on temperature variations. Regarding the pressure sensing application, pressure-induced capillary wall thickness variations were analytically accounted and related to the sys-tem pressure sensitivity. In both these applications, experimental data were presented. Finally, additional opportunities using specialty optical fibers were presented, namely, a photonic-crystal fiber-based dual-environment pressure sensor, a three parameters sensor using Bragg gratings, tapered fibers and multimode interference, a liquid-level sensor based on Bragg grat-ings and multimode interference, and a temperature sensor based in an embedded-core fiber filled with indium. The results reported herein demonstrates the potential of optical fibers for providing sensing platforms to attain measurements of different sort of parameters with highly sensitivity and improved resolutions
Doutorado
Física
Doutor em Ciências
152993/2013-4
CNPQ
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Issa, Nader. "Modes and propagation in microstructured optical fibres." University of Sydney. Physics and Optical Fibre Technology Centre, 2005. http://hdl.handle.net/2123/613.
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Microstructured optical fibres (MOFs), also commonly called photonic crystal fibres or holey fibres, describe a type of optical fibre in which continuous channels of (typically) air run their entire length. These `holes' serve to both confine electromagnetic waves within the core of the fibre and to tailor its transmission properties. In order to understand and quantify both of these functions, a new computational algorithm was developed and implemented. It solves for the eigenvalues of Maxwell's wave equations in the two-dimensional waveguide cross-section, with radiating boundary conditions imposed outside the microstructure. This yields the leaky modes supported by the fibre. The boundary conditions are achieved exactly using a novel refinement scheme called the Adjustable Boundary Condition (ABC) method. Two implementations are programmed and their computational efficiencies are compared. Both use an azimuthal Fourier decomposition, but radially, a finite difference scheme is shown to be more efficient than a basis function expansion. The properties of the ABC method are then predicted theoretically using an original approach. It shows that the method is highly efficient, robust, automated and generally applicable to any implementation or to other radiating problems. A theoretical framework for the properties of modes in MOFs is also presented. It includes the use of the Bloch-Floquet theorem to provide a simpler and more efficient way to exploit microstructure symmetry. A new, but brief study of the modal birefringence properties in straight and spun fibres is also included. The theoretical and numerical tools are then applied to the study of polymer MOFs. Three types of fibres are numerically studied, fabricated and characterised. Each is of contemporary interest. Firstly, fabrication of the first MOFs with uniformly oriented elliptical holes is presented. A high degree of hole ellipticity is achieved using a simple technique relying on hole deformation during fibre draw. Both form and stress-optic birefringence are characterized over a broad scaled-wavelength range, which shows excellent agreement with numerical modelling. Secondly, an analysis of leaky modes in real air core MOFs, fabricated specifically for photonic band gap guidance, is then used to identify alternative guiding mechanisms. The supported leaky modes exhibit properties closely matching a simple hollow waveguide, weakly influenced by the surrounding microstructure. The analysis gives a quantitative determination of the wavelength dependent confinement loss of these modes and illustrates a mechanism not photonic band gap in origin by which colouration can be observed in such fibres. Finally, highly multimode MOFs (also called `air-clad' fibres) that have much wider light acceptance angles than conventional fibres are studied. An original and accurate method is presented for determining the numerical aperture of such fibres using leaky modes. The dependence on length, wavelength and various microstructure dimensions are evaluated for the first time for a class of fibres. These results show excellent agreement with published measurements on similar fibres and verify that bridge thicknesses much smaller than the wavelength are required for exceptionally high numerical apertures. The influence of multiple layers of holes on the numerical aperture and capture efficiency are then presented. It shows that a substantial increase in both these parameters can be achieved for some bridge thicknesses. Simple heuristic expressions for these quantities are given, which are based on the physical insight provided by the full numerical models. The work is then supported by the first fabrication attempts of large-core polymer MOFs with thin supporting bridges. These fibres exhibit relatively high numerical apertures and show good agreement with theoretical expectations over a very wide scaled-wavelength range.
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Shankaranarayanan, N. K. "Mode-mode interference in optical fibers: analysis and experiment." Thesis, Virginia Tech, 1987. http://hdl.handle.net/10919/45891.
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Interference between the modes of an optical fiber generates specific mode (intensity) patterns which get modulated by disturbances in the optical fiber system. Mode-mode interference has been analyzed from first principles and a model based on differential phase modulation presented. Mode-mode interference effects such as intensity modulation of the mode patterns are directly related to differential phase modulation between modes which arises due to the difference between the propagation constants of the constituent modes. Practical implementation of modal methods involves selective launching of modes and processing of the output pattern to demodulate the information.
Axial strain has been chosen as the modulating mechanism in experiments designed to quantify mode-mode interference effects. Quasi-statically varying strain as well as vibrational strain was used to study 'dc' and 'ac' mechanisms. Specific mode combinations have been excited and their radiation patterns identified. Mode pattern changes have been described. Experimental observations and results correlate very well with analysis.
Master of Science
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Savojardo, Antonino. "Rare events in optical fibers." Thesis, University of Warwick, 2018. http://wrap.warwick.ac.uk/110215/.
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This thesis examines the topic of rogue waves and interacting quasi-solitons in optical fibers. We demonstrate a simple cascade mechanism that drives the formation and emergence of rogue waves in the generalized non-linear Schrödinger equation with third-order dispersion. Such generation mechanism is based on inelastic collisions of quasi-solitons and is well described by a resonant-like scattering behavior for the energy transfer in pair-wise quasi-soliton collisions. Our theoretical and numerical results demonstrate a threshold for rogue wave emergence and the existence of a period of reduced amplitudes — a "calm before the storm" — preceding the arrival of a rogue wave event. Using long time window simulations we observe the statistics of rogue waves in optical fibers with an unprecedented level of detail and accuracy, unambiguously establishing the long-ranged character of the rogue wave probability density function over seven orders of magnitude. The same cascade mechanism also generates rogue waves in the generalized non-linear Schrödinger equation with Raman term. To comprehend the physics governing rogue wave formation, we propose an experimental setup where soliton amplification is induced without third order dispersion or Raman term. In an optical fiber with anomalous dispersion, we replace a small region of the fiber with a normal dispersion fiber. We show that solitons colliding in this region are able to exchange energy. Depending on the relative phase of the soliton pair, we find that the energy transfer can lead to an energy gain in excess of 20% for each collision. A sequence of such events can be used to enhance the energy gain even further, allowing the possibility of considerable soliton amplification.
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Yu, Charles Xiao 1973. "Soliton squeezing in optical fibers." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86587.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2001.Includes bibliographical references (p. 113-122).
by Charles Xiao Yu.
Ph.D.
22
Silva, Nuno Alexandre Peixoto. "Quantum criptography in optical fibers." Doctoral thesis, Universidade de Aveiro, 2013. http://hdl.handle.net/10773/12214.
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Doutoramento em Engenharia EletrotécnicaAs comunicações quânticas aplicam as leis fundamentais da física quântica para codificar, transmitir, guardar e processar informação. A mais importante e bem-sucedida aplicação é a distribuição de chaves quânticas (QKD). Os sistemas de QKD são suportados por tecnologias capazes de processar fotões únicos. Nesta tese analisamos a geração, transmissão e deteção de fotões únicos e entrelaçados em fibras óticas. É proposta uma fonte de fotões única baseada no processo clássico de mistura de quatro ondas (FWM) em fibras óticas num regime de baixas potências. Implementamos essa fonte no laboratório, e desenvolvemos um modelo teórico capaz de descrever corretamente o processo de geração de fotões únicos. O modelo teórico considera o papel das nãolinearidades da fibra e os efeitos da polarização na geração de fotões através do processo de FWM. Analisamos a estatística da fonte de fotões baseada no processo clássico de FWM em fibras óticas. Derivamos um modelo teórico capaz de descrever a estatística dessa fonte de fotões. Mostramos que a estatística da fonte de fotões evolui de térmica num regime de baixas potências óticas, para Poissoniana num regime de potências óticas moderadas. Validamos experimentalmente o modelo teórico, através do uso de fotodetetores de avalanche, do método estimativo da máxima verossimilhança e do algoritmo de maximização de expectativa. Estudamos o processo espontâneo de FWM como uma fonte condicional de fotões únicos. Analisamos a estatística dessa fonte em termos da função condicional de coerência de segunda ordem, considerando o espalhamento de Raman na geração de pares de fotões, e a perda durante a propagação de fotões numa fibra ótica padrão. Identificamos regimes apropriados onde a fonte é quase ideal. Fontes de pares de fotões implementadas em fibras óticas fornecem uma solução prática ao problema de acoplamento que surge quando os pares de fotões são gerados fora da fibra. Exploramos a geração de pares de fotões através do processo espontâneo de FWM no interior de guias de onda com suceptibilidade elétrica de terceira ordem. Descrevemos a geração de pares de fotões em meios com elevado coeficiente de absorção, e identificamos regimes ótimos para o rácio contagens coincidentes/acidentais (CAR) e para a desigualdade de Clauser, Horne, Shimony, and Holt (CHSH), para o qual o compromisso entre perda do guia de onda e não-linearidades maximiza esses parâmetros.
The quantum communications apply fundamental laws of quantum physics to encode, transmit, store and process information. The most successful and important application is the quantum key distribution (QKD). The QKD systems are supported by technologies capable of processing single photons. In this thesis we analyze the generation, transmission and detection of single and entangled photons in optical fibers. We propose a single photon source based on the classical four-wave mixing (FWM) process in optical fibers in a low power regime. We implement that source in the laboratory, and we develop a theoretical model able to correctly describe the process of generation of single photons. That theoretical model takes into account the role of fiber nonlinearities and polarization effects on the generation of the photons through the FWM process. We analyze the statistics of the photon source based on the classical FWM process in optical fibers. We derive a theoretical model capable of describe the statistics of that photon source. We show that the photon source statistics goes from a thermal one in a low power regime to a Poissonian in a moderate power regime. We validate experimentally the theoretical results, using avalanche photo-detectors, the maximumlikelihood estimation method and the expectation-maximization algorithm. We study the spontaneous FWM process as a source of heralded single photons. We analyze the source statistics in terms of the conditional second-order coherence function, considering the impact of Raman scattering on the generation of the photon-pairs, and the loss during the evolution of the photon through a standard single mode fiber (SSMF). We identify appropriate regimes where that source is almost ideal. Optical fiber-based sources of photon-pairs provide a practical solution to the coupling problem that arises when the photon-pairs are obtained outside of the fiber. We explore the generation of photon-pairs through spontaneous FWM inside of waveguides with third-order electrical susceptibility. We describe the generation of the photon-pairs in a medium with non-negligible linear absorption coefficient, and we identified appropriates regimes for the coincidence-to-accidental ratio (CAR) and the CHSH inequality, for which the trade-off between waveguide losses and nonlinearities maximizes that parameters.
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Almeida, Álvaro José Caseiro de. "Quantum communications in optical fibers." Doctoral thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/16306.
Full textAbstract:
Doutoramento em Engenharia FísicaThis thesis begins by proposing the implementation of a probabilistic photon source based on the stimulated four-wave mixing (FWM) process. This source was implemented experimentally and characterized in terms of its statistical distribution. Next, the impact of the stimulated FWM process in a co-propagating quantum signal was studied experimentally. Finally, the violation of Clauser-Horne-Shimony-Holt (CHSH) inequality was experimentally verified using polarization-entangled photon pairs, which were obtained from the spontaneous FWM process in a Sagnac loop. The experimental evolution of the quantum-bit error rate (QBER) in a system without control of polarization, using this degree of freedom to encode information, was studied. It was found out that the QBER increases with the length of the transmission fiber. It was also verified that the increase in the QBER was due to the random rotation of photon’s polarization. A model for the rigorous estimation of the QBER was derived and developed an automatic method to compensate the random rotations of polarization. The method was validated numerically and experimentally, in a transmission system with 40km, showing that it can compensate for the rotations that photons suffer during propagation in optical fibers. Finally, a quantum bit commitment (QBC) protocol between two untrusted entities was implemented. The encoding was performed using two nonorthogonal states of polarization (SOPs). As quantum channel between the two entities, it was first assumed that the transmitter and the receiver were side by side, and after that, they were separated by 8 km and finally, that they were 16km from each other. The implementation of the protocol was performed with a success rate in measurements exceeding 93%, well above the theoretical security limit of 85%. The best strategy for deceiving the commitment was also implemented, and its security experimentally confirmed with a confidence of 7 standard deviations.
Nesta tese começou-se por propor a realização de uma fonte de fotões probabilística baseada no processo estimulado de mistura de quatro ondas (FWM). Implementou-se essa fonte no laboratório e caracterizou-se experimentalmente a sua distribuição estatística. Depois, estudou-se experimentalmente o impacto do processo estimulado de FWM num sinal quântico que se propaga na mesma fibra ótica. Por fim, foi verificada experimentalmente a violação da desigualdade de ClauserHorne-Shimony-Holt (CHSH) usando pares de fotões entrelaçados, que foram obtidos a partir do processo espontâneo de FWM num ciclo de Sagnac. Estudou-se a evolução da taxa de erro de bits quânticos (QBER) num sistema sem controlo de polarização, quando este grau de liberdade é usado para codificar a informação. Verificou-se que a QBER aumenta com o comprimento da fibra de transmissão. Verificou-se ainda que o aumento da QBER era devido às variações aleatórias da polarização dos fotões. Derivou-se um modelo para a estimativa rigorosa da QBER e desenvolveu-se um método automático de compensação das rotações aleatórias da polarização. O método foi validado numericamente e experimentalmente, num sistema de transmissão com 40km, verificando se que consegue compensar as rotações que os fotões sofrem durante a sua propagação em fibras óticas. Finalmente, implementou-se um protocolo de compromisso quântico entre duas entidades não confiávéis. Na codificação foram usados dois estados de polarização (SOPs) não ortogonais. Como canal quântico entre as duas entidades foi primeiro considerado que o emissor e o recetor se encontravam lado a lado, depois que estes estavam separados por 8km e finalmente que se encontravam a 16km um do outro. A implementação do protocolo foi feita com uma taxa de sucesso nas medidas superior a 93%, muito acima do limite teórico mínimo de 85%. Implementou-se ainda a melhor estratégia para que o compromisso pudesse ser falseado, tendo sido confirmada experimentalmente a sua segurança com uma confiança de 7 desvios padrão.
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Males, Mladen. "Suppression of transient gain excursions in an erbium-doped fibre amplifier /." Connect to this title, 2006. http://theses.library.uwa.edu.au/adt-WU2007.0157.
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Greene, Jonathan Andrew. "Photoinduced, refractive-index gratings in germanium-doped two-mode, elliptical-core optical fibers." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08222009-040313/.
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Kim, Jeong I. "Analysis and Applications of Microstructure and Holey Optical Fibers." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/29089.
Full textAbstract:
Microstructure and photonic crystal fibers with periodic as well as random refractive-index distributions are investigated. Two cases corresponding to fibers with one-dimensional (1D) radial index distributions and two-dimensional (2D) transverse index distributions are considered. For 1D geometries with an arbitrary number of cladding layers, exact analytical solutions of guided modes are obtained using a matrix approach. In this part, for random index distributions, the average transmission properties are calculated and the influence of glass/air ratio on these properties is assessed. Important transmission properties of the fundamental mode, including normalized propagation constant, chromatic dispersion, field distributions, and effective area, are evaluated. For 2D geometries, the numerical techniques, FDTD (Finite-Difference Time-Domain) method and FDM (Finite Difference Method), are utilized. First, structures with periodic index distributions are examined. The investigation is then extended to microstructure optical fibers with random index distributions.
Design of 2D microstructure fibers with random air-hole distributions is undertaken with the aim of achieving single-mode guiding property and small effective area. The former is a unique feature of the holey fiber with periodic air-hole arrangement and the latter is a suitable property for nonlinear fiber devices. Measurements of holey fibers with random air-hole distributions constitute an important experimental task of this research. Using a section of a holey fiber fabricated in the draw tower facility at Virginia Tech, measurements of transmission spectra and fiber attenuation are performed. Also, test results for far-field pattern measurements are presented.
Another objective of this dissertation is to explore new applications for holey fibers with random or periodic hole distributions. In the course of measuring the holey fibers, it was noticed that robust temperature-insensitive pressure sensors can be made with these fibers. This offers an opportunity for new low-cost and reliable pressure fiber-optic sensors. Incorporating gratings into holey fibers in conjunction with the possibility of dynamic tuning offers desirable characteristics with potential applications in communications and sensing. Injecting gases or liquids in holey fibers with gratings changes their transmission characteristics. These changes may be exploited in designing tunable optical filters for communication applications or making gas/liquid sensor devices.Ph. D.
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Lee, Shiao-Chiu. "Axial offset effects upon optical fiber sensor and splice performance." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/91128.
Full textAbstract:
A kind of intensity modulated fiber sensor utilizing axial offset parameter is proposed. The theoretical analysis and experimental characteristics of this sensor are described.
All the theoretical results derived in this thesis are based on assuming a uniform power distribution in the fibers. An expression of coupling efficiency of central dipped parabolic graded index fibers due to axial offset is derived. The results show less sensitivity to axial offset for the central dipped fibers than for the parabolic profile fibers without a dip. Expressions of coupling efficiency of graded index fibers due to axial offset for several different values of a are also derived. The results show that sensitivity increases as the value of a decreases. A general expression of coupling efficiency which is valid for small values of axial offset is derived. This expression exhibits a linear relationship between coupling efficiency and small axial offset.
Coupling efficiencies versus fiber end separation and axial offset of step index fibers have been measured. The measurements show that coupling efficiency is much more sensitive to axial offset than end separation. A simple construction of the axial offset fiber sensor is described. An approximate linear relationship between the output power and the mechanical loading has been obtained for this sensor. Several ways of increasing the sensitivity of this sensor are discussed.M.S.
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Ma, Nan. "Tailoring optical fibers for cell transfection." Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3177.
Full textAbstract:
Optical transfection is a promising technique for the delivery of foreign genetic material into cells by transiently changing the permeability of the cell membrane. Of the different optical light sources that have been used, femtosecond laser based transfection has been one of the most effective methods for optical transfection which is generally implemented using a free-space bulk optical setup. Here in this thesis, a few novel fabrication methods are devised to obtain easy and inexpensive fabrication of microlensed optical fibers, which can be used to replace traditional optical setup and perform femtosecond optical transfection. These fabrication methods offer the flexibility to fabricate a microlens which can focus femtosecond laser pulses at 800 nm to a small focal spot whilst keeping a relatively large working distance. In conventional optical transfection methods the foreign genetic material to be transfected is homogenously mixed in the medium. This thesis reports the first realization of an integrated optical transfection system which can achieve transfection along with localized drug delivery by combining lensed fiber based optical transfection system with a micro-capillary based microfluidic system. Finally, based on an imaging fiber (coherent optical fiber bundle), the first endoscope-like integrated system for optical transfection with subcellular resolution epifluorescence imaging was built. The transfection efficiency of these fiber based systems is comparable to that of a standard free-space transfection system. Also the use of integrated system for localized gene delivery resulted in a reduction of the required amount of genetic material for transfection. The miniaturized, integrated design opens a range of exciting experimental possibilities, such as the dosing of tissue slices to study neuron activities, targeted drug delivery, and in particular for using endoscope-like integrated systems for targeted in vivo optical microsurgery.
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Fructuoso, Garcia Alvaro. "Nonlinear Pulse Propagation in Optical Fibers." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19377.
Full textAbstract:
The project objective is to see how a pulse propagates along an optical fiber. This will take into account the linear effects of the fiber, as well as the nonlinear effects. Also be checked several commercial fiber types. And finally the propagation is carried to the limit to see how far it could spread without problems.
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Hesketh, G. "Nonlinear effects in multimode optical fibers." Thesis, University of Southampton, 2014. https://eprints.soton.ac.uk/374911/.
Full textAbstract:
Utilizing the modes of a multimode fiber forms a frontier between what is achievable with current fibre technology and what is required for the remainder of the 21st century. Large mode area multimode fibers accommodate the high power delivery demanded by fiber lasers used in industry for precision cutting, welding and drilling functions, and used elsewhere for the generation of white light sources used in fiber communication, medical and precision time keeping applications. This thesis explores the theory of nonlinear effects in multimode fibers with the intention of optimizing existing applications, whilst simultaneously identifying new ones. A generalized multimode nonlinear Schrodinger equation is numerically solved to explore the phenomenon of self-focusing in multimode fibers, with peak powers in the megawatt regime. Temporal effects compress femtosecond pulses launched into the fundamental mode, driving peak powers up and coupling power into higher order modes; a process identified with transverse spatial contraction and increased intensity. Parameter regimes in which damage may be avoided are identified. The nonlinear interaction of two modes under continuous wave pumping is solved analytically in terms of elliptic functions. The nonlinear multi frequency dynamics describing the optical regeneration of optical communication signals are researched in a scalar single mode scenario, before nonlinear effects in polarization modes are explored. In the scalar case, a modification to a phase sensitive amplifier from the literature solves the problem of phase to amplitude noise conversion during regeneration. Improved bit error rates in three modulation formats are simulated as a result and experimental collaboration demonstrates proof of principle. Polarization assisted phase sensitive amplification (PAPSA) for signal regeneration is then introduced. Polarization mode benefits include operating power and fiber length reduction, simultaneous regeneration of signal phase and amplitude, and a simple way to decompose the signal into quadrature and in-phase components. An approximate analytic theory of PAPSA is developed. Experimental collaboration demonstrates that PAPSA offers significant signal bit error rate reduction.
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Božinović, Nenad. "Orbital angular momentum in optical fibers." Thesis, Boston University, 2013. https://hdl.handle.net/2144/10943.
Full textAbstract:
Thesis (Ph.D.)--Boston UniversityInternet data traffic capacity is rapidly reaching limits imposed by nonlinear effects of single mode fibers currently used in optical communications. Having almost exhausted available degrees of freedom to orthogonally multiplex data in optical fibers, researchers are now exploring the possibility of using the spatial dimension of fibers, via multicore and multimode fibers, to address the forthcoming capacity crunch. While multicore fibers require complex manufacturing, conventional multimode fibers suffer from mode coupling, caused by random perturbations in fibers and modal (de)multiplexers. Methods that have been developed to address the problem of mode coupling so far, have been dependent on computationally intensive digital signal processing algorithms using adaptive optics feedback or complex multiple-input multiple-output algorithms. Here we study the possibility of using the orbital angular momentum (OAM), or helicity, of light, as a means of increasing capacity of future optical fiber communication links. We first introduce a class of specialty fibers designed to minimize mode coupling and show their potential for OAM mode generation in fibers using numerical analysis. We then experimentally confirm the existence of OAM states in these fibers using methods based on fiber gratings and spatial light modulators. In order to quantify the purity of created OAM states, we developed two methods based on mode-image analysis, showing purity of OAM states to be 90% after 1km in these fibers. Finally, in order to demonstrate data transmission using OAM states, we developed a 4-mode multiplexing and demultiplexing systems based on free-space optics and spatial light modulators. Using simple coherent detection methods, we successfully transmit data at 400Gbit/s using four OAM modes at a single wavelength, over 1.1 km of fiber. Furthermore, we achieve data transmission at 1.6Tbit/s using 10 wavelengths and two OAM modes. Our study indicates that OAM light can exist, and be long lived, in a special class of fibers and our data transmission demonstrations show that OAM could be considered an additional degree of freedom for data multiplexing in future optical fiber communication links. Our studies open the doors for other applications such as micro-endoscopy and nanoscale imaging which require fiber based remote delivery of OAM light.
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Tantiphanwadi, Prapassorn. "Intrinsic Loss in Infrared Optical Fibers." DigitalCommons@USU, 1992. https://digitalcommons.usu.edu/etd/2098.
Full textAbstract:
Recently, in communication system, fiber optics has become a most interesting development tool as a transmission medium. It first appeared as a feasible transmission medium in 1970. The reason for the development in fiber optics comes from the overwhelming advantage in technology and economy compared to wires and coaxial links. For technology progress, typically, optical fiber has a wide transmission band-width (0.1-1000 GHz), lower loss per unit length (0.15 – 5 dB km ^-1[1]), and does not allow electromagnetic interference. For example, signal transmitted over commercial silica-based fiber must be reamplified every 10 to 50 kilometers, whereas signals transmitted over copper wires must be reamplified every 4 to 6 kilometers. The economical advantage are as follows: a typical cable fiber weighs only about 3 kg/km; cost under $500/km or less, and has a longer repeater spacing of up to 100 km or more at a data rate of at least several hundred megabits per second. Because the optical fibers meet both demands, it has enabled us to construct high bit-rate and long haul communication systems in metropolitan area.
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Andrews, Jeffrey Pratt. "Longitudinal misalignment based strain sensor." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43283.
Full textAbstract:
A practical fiber optic strain sensor has been developed to measure strains in the range of 0.0 to 2.0 percent strain with a resolution ranging between 10 and 100 microstrain depending on sensor design choices. This intensity based sensor measures strain by monitoring strain induced longitudinal misalignment in a novel fiber interconnection. This interconnection is created by aligning fibers within a segment of hollow core fiber. Related splice loss mechanisms are investigated for their effect on resolution. The effect of gauge length and launch conditions are also investigated.
Master of Science
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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.
Full textAbstract:
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
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Gharbia, Yousef Ahmed Mechanical & Manufacturing Engineering Faculty of Engineering UNSW. "Nano-grinding for fabrication of microlenses on optical fibers endfaces." Awarded by:University of New South Wales. School of Mechanical and Manufacturing Engineering, 2003. http://handle.unsw.edu.au/1959.4/20735.
Full textAbstract:
This work presents mechanical nano-grinding as an alternative technique for the fabrication of optical fibers endface microlenses. It also presents a novel surface-roughness improvement technique called Loose Abrasive Blasting (LAB). Traditionally, the majority of such microlenses are made using either chemical etching or heating and pulling methods. Despite the success of these methods, they suffer some common drawbacks such as the lack of controllability on the produced lens profile. Consequently the possible variations of the lens profiles that can be made by these methods are also limited. The difficulty to center the lens on the fiber core is another problem associated with heating and pulling method. The exposure to hazardous chemical such as hydrofluoric acid is yet another problem associated with chemical etching. Nano-grinding technique described in this thesis should provide a much better alternative to the traditional optical fabrication techniques. Nano-grinding experiments were conducted on a nano-grinding machine (NGM) specially built for this purpose. The machine incorporates state-of-the-art air-bearing spindles, piezo electric actuators, and capacitive displacement sensors with accuracy down to 2 nm. Such precise motion provided by this system is the key for the success of this technique. With such system, it was possible to produce a multitude variety of lens profiles with high profile accuracy and with surfaces of optical quality without the need for exposure to any kind of hazardous chemicals. In achieving this objective, the research was conducted on many frontiers. First, the possibility of grinding optical fibers without inducing surface and subsurface damages was investigated. Micro-indentation, nano-indentation, and nano-scratch tests were conducted to determine the critical depth of cut that can be achieved before the occurrence of surface and subsurface cracks. Nano-scratch test in particular provided a clear insight to the cracking and the chipping mechanisms that might unfold if the critical depth of cut was exceeded in an actual grinding situation. The knowledge gained from this exercise laid the ground base for the design of the NGM. Using the NGM, further experiments were carried out to determine the optimal grinding parameters for an efficient and successful grinding process. Parameters investigated include the grit size, the cutting speed, and the in-feed rates. The optimum parameters have to ensure the best endface surface quality and the same time maintain a high throughput. This study shows that based on these optimal parameters, it should be possible to produce endface microlenses of optical surface quality free surface and/or subsurface damages in less than 30 seconds with surface roughness (Ra) less than 3 nm. A novel post-grinding surface improvement techniques was also developed. The technique called loose abrasive blasting (LAB) can be used for polishing at and non-flat surfaces. Experiments were conducted on a loose abrasive blasting machine built specially for this purpose. The performance of this technique was compared with other techniques such as slurry polishing and chemical etching used for polishing of brittle materials. The results showed that while chemical etching was found unsuitable for polishing of at optical fiber endfaces, LAB outperformed slurry polishing by significant margin. After the optimal grinding conditions were established, the NGM was used for grinding of different kinds of optical fiber microlens profiles. Among the endface profiles produced were conical lenses, tapered lenses, D-shaped lenses and others. It has also been shown, in case of conical lenses for instance, that there is almost unlimited number of profiles that can be produced by simply changing the contact angle between the fiber endface and the grinding film. The effect of surface roughness on light coupling efficiency between a fiber endface and a laser diode was also investigated. Cleaved fiber endfaces as well as ground endfaces with variant degrees of surface roughness were used in this experiment. The results showed that surface roughness has significant effect on light coupling efficiency. The effect of lens eccentricity on light coupling was also investigated.
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Waalib-Singh, Nirmal. "Metastable entangled ordered structures in predeformed and preconditioned polymer optical fibres." Thesis, The University of Sydney, 2008. https://hdl.handle.net/2123/28122.
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The nature of fibre optics transmission has been the subject of various studies since the first optical fibres were discovered and manufactured in the early 1960's. However, to date, few have investigated, let alone correlated results from the mechanical and thermal testing of these fibres with respect to those optical properties that are usually reported.
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Feth, Shari. "Sapphire optical fiber sensors." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-12232009-020350/.
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Hattori, Haroldo Takashi. "Low Nonlinearity Optical Fibers for Broadband and Long-Distance Communications." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/29816.
Full textAbstract:
A class of low nonlinearity dispersion-shifted and dispersion-flattened fibers for
broadband and long haul applications is presented. The refractive index profiles of these
fibers assume a depressed-core multi-clad geometry in order to achieve effective-areas
much larger than those in conventional optical fibers.
A systematic approach for designing large effective-area dispersion-shifted fibers, using a
reference W-index profile to initiate the design, is presented. Transmission properties,
including effective-area, mode-field-diameter, dispersion, dispersion slope, cutoff
wavelength, and bending, microbending and splice losses are evaluated for several design
examples. To ascertain that the proposed fibers can be practically fabricated, the effects
of varying fiber dimensions and indices on effective-area, mode-field-diameter and
dispersion are assessed.
It is shown that there is a trade-off between effective-area and mode-field-diameter and,
generally, larger effective-areas are associated with larger mode-field-diameters. In other
words, less signal distortion due to fiber nonlinearity (larger effective-area) is associated
with higher power loss due to bending of fiber (larger mode-field-diameter). Thus, a large
effective-area and low bending loss are conflicting requirements. A parameter Q is
defined as a performance indicator, considering effective-area and mode-field-diameter.
Dispersion-shifted single-mode fiber designs with effective-areas of 78 mm
2 to 210 mm2 and the corresponding mode-field-diameter of 8.94 mm to 14.94 mm,
dispersion less than 0.07 ps/nm.km, and dispersion slope of about 0.05 ps/ nm2.km are
presented. Numerical simulations for propagation of pulses in few designed fibers are
performed.Designs of large effective-area dispersion-flattened fibers are also presented,
for the first time we believe. These fibers provide large effective-area and low dispersion
over an extended range of wavelengths. For our design, over the wavelength range of 1.48 mm <
l < 1.58 mm, the effective-area is 75 mm2 to 100 mm2, while the dispersion remains
below 0.7 ps/nm.km.Ph. D.
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Shen, Linping Huang Wei-Ping. "Modeling and design of photonic crystal waveguides and fibers /." *McMaster only, 2003.
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Goel, Nitin Kumar. "Development of "Core-Suction" Technique for Fabrication of Highly Doped Fibers for Optical Amplification and Characterization of Optical Fibers for Raman Amplification." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29302.
Full textAbstract:
This thesis presents a novel technique named "Core Suction" for fabricating optical fiber preforms for manufacturing highly doped fibers (HDFs) for optical amplification (Raman effect based or Erbium fiber based). The technique involves drawing the molten non-conventional core glass material into the silica cladding tube to form the preform. The developed technique is simple, inexpensive and shows great potential for fabricating preforms of highly nonlinear non-conventional multi-component glasses as the core material. Preforms were made with various core glasses such as Schott SF6, Lead-Tellurium-Germanate, Lead-Tellurium-Germanate- Neodymium -Erbium and MM2 in silica cladding tubes and then pulled into fibers.
The fabricated fibers were measured for refractive index profile, loss spectrum and spontaneous Raman spectra. Elemental analysis of the fiber samples was also performed using an electron microprobe. Erbium doped fiber amplifiers (EDFAs) were setup using 30 cm, 5cm and 1 cm lengths of fabricated erbium doped fibers and their gain spectra measured. The distributed gain spectrum for an EDFA was also measured using an optical frequency domain reflectometery (OFDR) technique. Commercial dispersion compensated fiber (DCF) with very high GeO2 doping was used to setup a Raman amplifier and the gain spectrum measured.
One of the needs of Raman amplification in optical fibers is to predict an accurate Raman gain, based on the fiber's refractive index profile. A method of predicting Raman gain in GeO2 doped fibers is presented and the predicted Raman gain values are compared with the measured ones in the same fibers. Raman gain issues like the dependence of the Raman gain on the GeO2 concentration, polarization dependence were taken into account for the gain calculations. An experimental setup for Raman gain measurements was made and measurement issues addressed. Polarization dependence of the Raman gain in one kilometer of polarization maintaining fiber was also measured.Ph. D.
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Conley, Jill Anne. "Hygro-thermo-mechanical behavior of fiber optic apparatus." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/17308.
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Lu, Ping. "Characterization and application of optical fibers: 1. Application of optical fibers in gas concentration and radiation dose measurements. 2. Polarization effects in fiber communication systems." Thesis, University of Ottawa (Canada), 2002. http://hdl.handle.net/10393/6320.
Full textAbstract:
The thesis consists of two research directions: Optical fiber applications in gas concentration and radiation dose measurements; and polarization effects in fiber optic communication systems. Part I of the thesis presents two optical fiber applications. (1) An infrared (IR) fiber bundle has been designed and fabricated to measure gas concentrations in a chemical vapor deposition (CVD) chamber using Fourier transform infrared spectroscopy. This fiber bundle covers the IR range from 0.5 to 20 mum and reduces the light beam divergence in the CVD chamber, which makes it possible to measure gas concentrations in a region near the substrate surface. Semi-ellipsoid mirrors have been designed and used to increase the collection efficiency of infrared radiation and to compensate the loss introduced by the fiber bundle. (2) A fiber optic radiation sensor based on radiation-induced fiber loss is reported. The gamma radiation-induced loss spectra in various fibers have been studied. Among all the fibers tested, 5% P-doped fiber shows the highest sensitivity to gamma radiation. The wavelength and dose rate dependence of radiation-induced loss in 5% P-doped fiber are investigated and the possibility of using this fiber as a radiation sensor for radiation therapy is discussed. Part II of the thesis examines two polarization effects, polarization mode dispersion (PMD) and polarization dependent loss (PDL), in fiber optic communication systems based on the waveplate models. A new waveplate model, capable of generating any PMD and PDL values, is proposed to overcome the limitations of the conventional waveplate model. Using both models the statistical distributions of PDL and differential group delay (DGD) have been studied considering the presence of biased elliptical birefringence. The principal state of polarization (PSP) of an optical pulse is proposed for a fiber having both PMD and PDL. PMD and PDL of a pulse for a fiber consisting of two polarization maintaining fiber segments are calculated, and the pulse distortions due to PMD and PDL are analyzed. PMD and PDL impact on digital communication systems have been studied in terms of system Q factor, bit error rate (BER) and system outage probability. The acceptable PMD values in a system with PDL are discussed for various power margins. The Q factor distributions due to PDL and its combination with PMD have been measured experimentally and compared to numerical simulations.
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Sousa, Carlos MaurÃcio de. "Estudo numÃrico do acoplador duplo simÃtrico nÃo linear de fibras de cristais fotÃnicos sob modulaÃÃo ppm." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=9383.
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Neste trabalho, apresentamos uma anÃlise numÃrica para a obtenÃÃo de portas lÃgicas totalmente Ãpticas, baseadas em um Acoplador Direcional NÃo-Linear Duplo SimÃtrico (NLDC) em fibras de cristais fotÃnicos (PCF) sem perda, trabalhando com pulsos ultracurtos de 100 fs(femtosegundos), para a obtenÃÃo de portas lÃgicas E/OU, sob ModulaÃÃo por PosiÃÃo de Pulsos (PPM). A investigaÃÃo à realizada atravÃs de simulaÃÃes numÃricas, utilizando-se o mÃtodo de Runge-Kutta de quarta ordem. Considerando a operaÃÃo das portas lÃgicas, foram utilizadas as quatro possÃveis combinaÃÃes para dois pulsos nas entradas das fibras 1 e 2, modulados pela posiÃÃo temporal (PPM) nos nÃveis lÃgicos 0 ou 1. Foram investigados, inicialmente, os efeitos de uma variaÃÃo no parÃmetro de ajuste PMM (ε) no deslocamento do pulso de saÃda em cada uma das fibras; em seguida, foram investigados os efeitos da diferenÃa de fase(ΔФ) entre os pulsos sÃlitons fundamentais de entrada, devidamente modulados, no deslocamento do pulso de saÃda em cada uma das fibras. Nas duas aplicaÃÃes, foram levados em consideraÃÃo a dispersÃo de velocidade anÃmala de grupo (GVD), a dispersÃo de segunda ordem (β2), a dispersÃo de terceira ordem (β3) e os efeitos nÃo-lineares SPM, SS e IRS. Os resultados indicam que à possÃvel a obteÃÃo de portas lÃgicas OU utilizando um controle de fase para um pulso de entrada.In this work, we present a numerical analysis for obtaining all-optical logic gates based on a Directional Coupler Nonlinear Symmetric Double (NLDC) in photonic crystal fibers (PCF) without loss, working with ultrashort pulses of 100 fs (femtoseconds) , to obtain gates AND / OR under Pulse Position Modulation (PPM). Research is conducted through numerical simulations, using the Runge-Kutta fourth order. Considering the operation of logic gates were used the four possible combinations to the inputs of two pulses fibers 1 and 2, the temporal position modulated (PPM) in the logic levels 0 or 1. Were investigated initially, the effects of a change in tuning parameter PMM (ε) in the displacement of the output pulse in each fiber, then we investigated the effects of the phase difference (ΔФ) between pulses of fundamental solitons input, suitably modulated, at offset output pulse in each fiber. In both applications, were considered anomalous dispersion of group velocity (GVD), second order dispersion (β2), the third-order dispersion (β3) and nonlinear effects SPM, SS and IRS. The results indicate that it is possible to achievement OR logic gate using phase control to an input pulse.
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Gapontsev, Denis Valentinovitch. "Fiber Raman lasers and amplifiers and their applications." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322403.
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Appajaiah, Anilkumar. "Climatic stability of polymer optical fibers (POF)." Phd thesis, [S.l. : s.n.], 2004. http://pub.ub.uni-potsdam.de/2004/0066/appaji.pdf.
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Saravanos, Constantine. "Operational window of single-mode optical fibers." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10834.
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The purpose of this Ph.D. thesis is to define the design window of single-mode dispersion-unshifted fibers. This window, defined in the mode field diameter (MFD) and cutoff wavelength (lambda c) plot is determined by the fiber properties with regards to the chromatic dispersion, the bend loss sensitivity at 1550 nm and the modal noise penalty imposed on high speed operating systems. This has been achieved by developing numerical models used to analyze the properties of optical fibers. These models were used to calculate the propagation characteristics of optical fibers and from them their physical properties, such as the dispersion and bending loss of the fundamental mode. Similar programs, used in the calculations of the LP11 mode attenuation and bend performance, determined the fiber's modal noise sensitivity and from it the upper limit of cutoff wavelength.
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Ademgil, Huseyin. "Optical properties of novel photonic crystal fibers." Thesis, University of Kent, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509653.
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Banaei, Esmaeil. "Polymer Optical Fibers for Luminescent Solar Concentration." Doctoral diss., University of Central Florida, 2013. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/5898.
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Luminescent solar concentrators (LSC's) are promising candidates for reducing the cost of solar power generation. Conventional LSC's are slab waveguides coated or doped with luminescence materials for absorption and guiding of light to the slab edges in order to convert optical energy into electricity via attached photovoltaic (PV) cells. Exploiting the advantages of optical fiber production, a fiber LSC (FLSC) is presented in this thesis, in which the waveguide is a polymeric optical fiber. A hybrid fiber structure is proposed for an efficient two-stage concentration of incident light, first into a small doped core using a cylindrical micro-lens that extends along the fiber, and second to the fiber ends by guiding the fluoresced light from the active dopants. Flexible sheets are assembled with fibers that can be bundled and attached to small-area PV cells. Small dimensions and directional guiding of the fibers allow for approximately one order of magnitude geometrical gain improvement over that of existing flat LSC's. In addition, the undesired limit of LSC size is eliminated in one direction.
Modeling and optimization of an FLSC design is presented using polarization-ray tracing under realistic conditions with solar spectrum radiation and broad-band absorption and emission spectra of fluorescence materials with their inevitable self-absorption effect.
Methods and results of fabrication and accurate optical characterization of such FLSC using two off-the-shelf organic dyes and a commercially available polymer, COP, are discussed in detail. Fiber preforms, fabricated under optimized conditions for low light transport loss, are thermally drawn into sub-millimeter-size fibers. Characterization of several samples with various concentrations of the two dyes shows an optical-to-optical conversion efficiency of 9.1% for a tandem combination of two 2.5-cm-long fibers with the efficiency gradually decreasing to 4.9% with increase in fiber length to 10 cm.Ph.D.
Doctorate
Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering
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KAWASE, LILIANA ROCHA. "BRAGG GRATING IN OPTICAL FIBERS AND APPLICATIONS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1997. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8454@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFINANCIADORA DE ESTUDOS E PROJETOS
O objetivo principal deste trabalho foi o de estudar as redes de Bragg em fibras ópticas e suas principais aplicações, com especial interesse na compensação de dispersão de pulsos ópticos em sistemas de telecomunicações, onde uma implementação original foi construída. Faz-se uma revisão geral das técnicas existentes para fabricá-las e caracterizá-las, além de suas principais aplicações, não somente na área de telecomunicações mas também na área sensoriamento óptico. São mostrados os resultados experimentais obtidos nas montagem realizadas para escrever redes de Bragg em fibras ópticas e para caracterizá-las. Algumas experiências usando redes de Bragg para o controle do comprimento de onda de emissão de um laser de semicondutor e para medição de força aplicada numa estrutura são mostradas. São mostrados também os resultados experimentais inéditos obtidos com a compensação de dispersão de pulsos ópticos em enlaces de telecomunicações, onde várias montagens foram realizadas para comprovar a superioridade da utilização da redes de Bragg para esse fim. Demonstra-se também um sistema para gerar pulsos solitônicos sintonizável em comprimento de onde numa faixa de MHZ. Finalmente são mostrados os resultados obtidos com a utilização de fibras ópticas para chaveamento interferométrico de luz. Neste sistema são utilização como elemento óptico não linear fibras tipo D, com e sem redes de Bragg, revestidas com filme de materiais semicondutores amorfos.
Bragg grating in optical fibers are used to compensate the dispersion of optical pulses in telecommunication systems. Initially, an overview is presented of the existing fabrication techniques of such gratings, as well as the techniques used for characterization. Some useful applecations in telecommunications and sensing are also shown. The results obtained in the set-up to write and to characterize Bragg gratings are presented. Some measurements were also done with typical applications such as controlling the emitting wavelength in semiconductors lasers, and monitoring the applied pressure in an optical fiber. Some new results are described on dispersion compensation in fibers. Using specially chirped Bragg gratings to pre- compensatedispersion of an optical pulse in a 80 km fiber link, we demonstrated that the poor quality of the input laser pulses has little impact on the duration of the pulses recovered after transmission. Finally, an interferometric switching arrangement using a semiconductor coated D fiber as nonlinear control element, is presented. The configuration uses infrared optical pulses to control a continuous wave light signal. It is also shown that the original reflected wavelength of a semiconductor coated D-fiber with Bragg grating can be shited with an external optical control signal.
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Forsberg, Frans. "Gas Analysis using Hollow-Core Optical Fibers." Thesis, KTH, Tillämpad fysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-231924.
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