This thesis examines polarization and polarization mode dispersion (PMD) dynamics in optical fibers as well as the evaluation of probability density functions and bit error rates in a realistic wavelength division multiplexed (WDM) optical communication systems. In the first part of the thesis, experimental studies of the dynamics of polarization in a dispersion compensation module (DCM) are performed in which mechanical shocks are imparted to several different DCMs by dropping a steel ball on the outer casing at different locations and from different heights and the resulting rapid polarization fluctuations are measured. We provide a theoretical model that accounts for the dynamic birefringence generated due to the impact. Next, an experimental technique is proposed to detect the location of temporal polarization activity in WDM systems. It is demonstrated theoretically and in simulations that measurement of both the PMD vector and the Stokes parameters at the WDM frequencies enables the detection of the location of such activity. Different linear prediction procedures are applied to the differential group delay of an optical fiber link assumed to obey the hinge model. The hinges are modeled as polarization rotators with fixed rotation axes and sinusoidally varying rotation angles. Three prediction methods are investigated and consequently compared: an autoregressive model (AR) with Kalman filter, a pattern imitation method and a Taylor expansion technique. The effect of measurement noise on the prediction horizon is also investigated for each prediction method. Using a physically reasonable stochastic model for the hinges, we derive analytical expressions for the temporal autocorrelation functions of the state of polarization (SOP) and the PMD vector. The obtained analytical results are compared to simulations. Finally, we apply the multicanonical method to the probability density function of received symbols and the symbol error ratio (SER) in a dual polarization quadrature phase shift keyed (DP-QPSK) WDM system. We simulate five co propagating channels at a symbol rate of 10.7 GBaud/s and account for PMD and nonlinear effects. We evaluate the performance of the system for two different cases: single mode fibers with full dispersion compensation at the end of the link, effective large area fibers (LEAF) with full dispersion compensation at the end of the link.

This thesis examines polarization and polarization mode dispersion (PMD) dynamics in optical fibers as well as the evaluation of probability density functions and bit error rates in a realistic wavelength division multiplexed (WDM) optical communication systems. In the first part of the thesis, experimental studies of the dynamics of polarization in a dispersion compensation module (DCM) are performed in which mechanical shocks are imparted to several different DCMs by dropping a steel ball on the outer casing at different locations and from different heights and the resulting rapid polarization fluctuations are measured. We provide a theoretical model that accounts for the dynamic birefringence generated due to the impact. Next, an experimental technique is proposed to detect the location of temporal polarization activity in WDM systems. It is demonstrated theoretically and in simulations that measurement of both the PMD vector and the Stokes parameters at the WDM frequencies enables the detection of the location of such activity. Different linear prediction procedures are applied to the differential group delay of an optical fiber link assumed to obey the hinge model. The hinges are modeled as polarization rotators with fixed rotation axes and sinusoidally varying rotation angles. Three prediction methods are investigated and consequently compared: an autoregressive model (AR) with Kalman filter, a pattern imitation method and a Taylor expansion technique. The effect of measurement noise on the prediction horizon is also investigated for each prediction method. Using a physically reasonable stochastic model for the hinges, we derive analytical expressions for the temporal autocorrelation functions of the state of polarization (SOP) and the PMD vector. The obtained analytical results are compared to simulations. Finally, we apply the multicanonical method to the probability density function of received symbols and the symbol error ratio (SER) in a dual polarization quadrature phase shift keyed (DP-QPSK) WDM system. We simulate five co propagating channels at a symbol rate of 10.7 GBaud/s and account for PMD and nonlinear effects. We evaluate the performance of the system for two different cases: single mode fibers with full dispersion compensation at the end of the link, effective large area fibers (LEAF) with full dispersion compensation at the end of the link.

[pt] O campo de estudo com estruturas origami tem crescido nos últimos anos como soluções inovadoras para problemas em ciência e engenharia. As primeiras aplicações aproveitaram a ideia de que um sistema estrutural pode ser dobrado de forma compacta e subsequentemente estendido, ou que a automontagem pode ser usada para construir uma estrutura tridimensional inspirada em uma folha fina. O presente trabalho apresenta comparações entre o modelo de barra e dobradiça com os modelos mais simples possíveis de elementos finitos híbridos de placa e casca para a representação de painéis de estruturas origami. O modelo de barra e dobradiça traz uma abordagem baseada na modelagem do estado parcialmente dobrado de painéis com uma estrutura de treliça articulada, onde as dobras são as barras, e os vértices as articulações. Os modelos de casca e placa utilizam a formulação híbrida dos elementos finitos, que tem como base o potencial de Hellinger-Reissner, que permite a aproximação dos campos de tensões satisfazendo a equação de equilíbrio do problema de elasticidade, e campos de deslocamento que atendem a compatibilidade no contorno. Exemplos numéricos mostram o comportamento mecânico dessas estruturas e a energia para realização das dobras através de autovalores dos respectivos automodos. É feita também uma avaliação dinâmica dos modelos para montagens estruturais com uma, duas e quatro células. / [en] Research works involving structural origami have grown in recent years, especially applied to science and engineering problems. Early applications took advantage of the idea that a system can be folded compactly and subsequently deployed, and that self-assembly can be used to construct a three dimensional structure by starting from a thin sheet. The present work compares bar and hinge models with the simplest hybrid finite element models for plate and shell in order to represent origami structure panels. The hybrid finite element formulation is based on the Hellinger-Reissner potential for an approximation of the stress field, thus satisfying the equilibrium equation of the elasticity problem in the domain. The bar and hinge model approach, as given in the literature, is based on folded patterns as pin-jointed truss frameworks. Each vertex in the folded sheet is represented by a pin-joint, and every fold line by a bar element. Numerical examples show the mechanical behavior of these structures and the folding energy using eigenvalues of the respective eigenmodes. Dynamic analysis of the models is also carried out for structure assemblages with one, two and four cells.

Combining the most recent technologies in concrete, Ultra-High-Performance Fibre-Reinforced Concrete (UHPFRC) arises as a promising material for the near future. UHPFRC have shown how flexible concrete can be to adapt to the ever-changing social and environmental demands. With its high flexibility composition and its mechanical properties, UHPFRC is full of both unexplored and unexploited possibilities. Engineers should take responsibility for this task. However, it is fair to acknowledge that this is not an easy task and it requires the development of reliable and widely accepted design standards provided by the scientific community. A major concern about durability, long-lasting structures and reduction of maintenance cost, as well as the development of new concrete technologies, improved knowledge of fibre effect and a huge growth in the fibre industry accompanied by fibre price reduction have led, among other factors, to the development of new types of concrete whose mechanical behaviour substantially differs from conventional fibre-reinforced concrete. This is why current characterisation methodologies and design standards must be reviewed and adjusted to these newer materials. However, design standard revision cannot disregard former milestones achieved thanks to decades of hard work. It must offer an integrated view in which new types of concrete comprise existing ones in a broader group, because at the end of the day and despite having newer and improved properties, new types of concrete are still concrete. That is how it should be understood and how it must be reflected in newer codes and standards. The work presented herein is focused on one of these recently developed materials that embraces major advanced technologies in concrete: Ultra-High-Performance Fibre-Reinforced Concrete (UHPFRC). This work is specifically focused on those crucial requirements for the development and widespread use of it, such as constitutive tensile characterisation and classification. This work includes a deep revision of the uniaxial tensile behaviour of concrete and its development as fibre technology has evolved. In addition, traditional characterisation standard methods as well as those recently developed for its specific use on UHPFRC are reviewed and called into question. Throughout the document, the development of different methodologies to determine the uniaxial constitutive tensile behaviour of UHPFRC from bending tests are shown, together with a simplified characterisation proposal specially developed for being included in a standard. All developed methodologies presented herein are checked and validated. These methods are specifically designed for their application on experimental results obtained from a special type of four-point bending test, whose standardisation proposal for UHPFRC is also shown. Finally, a classification proposal is presented as a function of more relevant UHPFRC tensile parameters necessary for design that can be directly obtained from the standard characterisation test method suggested. Proposed classification encompasses the existing classification for conventional reinforced and fibre-reinforced concrete. In it, both plain concrete and fibre-reinforced concrete are presented as a particular case of a more general tensile constitutive response for concrete. Standard methodology and classification proposed are in accordance with the evolution of concrete and unify historic milestones achieved by the international research community. / El Hormigón de Muy Alto Rendimiento (HMAR) combina los últimos avances tecnológicos en hormigón y se erige como un material prometedor para el futuro. El HMAR ha demostrado su gran capacidad para adaptarse a las cada vez más exigentes demandas sociales y medioambientales. Con un gran abanico de posibilidades en su dosificación para conseguir las propiedades mecánicas deseadas, el HMAR es un material lleno de posibilidades aún sin explorar y sin explotar. Los ingenieros tienen la responsabilidad de esta tarea. Sin embargo, es justo reconocer que no se trata de una tarea fácil y que requiere de un desarrollo previo de códigos de diseño adecuados y ampliamente aceptados por parte de la comunidad científica. La aparición de nuevas tecnologías, el mayor conocimiento sobre la aportación de las fibras así como su industrialización y bajada de precios, las mayores preocupaciones sobre la durabilidad estructural, incremento de la vida útil o la reducción de los costes de mantenimiento, entre otros factores, han derivado en el desarrollo de nuevas tipologías de hormigones cuyo comportamiento mecánico difiere de manera sustancial de los tradicionales hormigones con fibras. Es por ello que tanto la readaptación de las metodologías de caracterización como las metodologías de diseño deben ser reformuladas. Y esto debe hacerse de manera no disruptiva, es decir, manteniendo la línea de los hitos alcanzados en los hormigones con fibras convencionales de manera que queden integrados en metodologías de caracterización y de diseño que los engloben, porque al fin y al cabo, y aunque con nuevas y mejores propiedades mecánicas, los nuevos hormigones siguen siendo hormigones. Así debe ser entendido y así debe quedar reflejado en las nuevas normativas. El presente trabajo se centra en uno de esos nuevos materiales desarrollados con el avance de las nuevas tecnologías como es el HMAR. En especial, este documento se centra en ese aspecto tan fundamental para el desarrollo de nuevos hormigones como es la caracterización mecánica y la tipificación. Este trabajo incluye una revisión del comportamiento mecánico uniaxial a tracción del hormigón y de su evolución con la aparición de las diferentes tecnologías. Además, se revisan y se ponen en cuestión los sistemas tradicionales de caracterización, así como los nuevos sistemas desarrollados en los últimos años para su empleo específico en el HMAR. A lo largo del documento se desarrollan diferentes metodologías para la obtención del comportamiento constitutivo a tracción del HMAR, así como la propuesta de una metdología simplificada de caracterización especialmente diseñada para ser incluida en una norma, todas ellas debidamente validadas. Estas metodologías son de aplicación específica a los resultados experimentales obtenidos mediante un ensayo a cuatro puntos sin entalla, cuya propuesta de estandarización para el HMAR ha sido también desarrollada. Finalmente, se presenta una propuesta de tipificación de acuerdo a los parámetros más relevantes del comportamiento a tracción del HMAR que son necesarios para el diseño y que pueden ser directamente obtenidos del ensayo de caracterización propuesto. Esta clasificación engloba a la clasificación existente para el hormigón armado convencional y los actuales hormigones con fibras, de manera que se presenta la actual definición de hormigón con fibras como un caso particular de estos nuevos hormigones, respetando al máximo la evolución de este material y aunando los logros conseguidos por la comunidad científica. / Dins de les combinacions de les tecnologies més recents en el formigó, el formigó de molt alt rendiment (UHPFRC) sorgeix com un material prometedor per al futur pròxim. L'UHPFRC ha demostrat poder ser un formigó flexible per adaptar-se a les sempre canviants demandes socials i mediambientals. Amb una gran flexibilitat en la seua composició i les seues propietats mecàniques, l`UHPFRC està ple de possibilitats de ser explorades i explotades. Els enginyers han de prendre la responsabilitat d'aquesta tasca. No obstant això, és just reconèixer que això no serà fàcil i requerirà el desenvolupament de normes de disseny fiables i àmpliament acceptades per la comunitat científica. Hi ha una gran preocupació al voltant de la durabilitat, la vida útil de les estructures i la reducció del cost de manteniment, juntament amb el desenvolupament de noves tecnologies de formigó, un millor coneixement de l'efecte de la fibra i un enorme creixement en la indústria de la fibra acompanyat per la reducció del preu de la fibra, han conduït, entre altres factors, al desenvolupament de nous tipus de formigons, el comportament mecànic dels quals es diferencia substancialment dels formigons reforçats amb fibres convencionals. És per això que les metodologies de caracterització actuals i les normes de disseny han de ser revisades i ajustades a aquests nous materials. No obstant això, la revisió del codis de disseny no pot prescindir de les antigues fites aconseguides gràcies a dècades de treball dur. S'ha d'oferir una visió integrada en la qual els nous tipus de formigons integren els ja existents en un grup més ampli, ja que, al cap i la fi i malgrat tenir propietats noves i millorades, els nous tipus de formigons són encara un tipus de formigó. Així es com s'hauria d'entendre i reflectir-se en els nous codis i normes. El treball presentat en aquest document es centra en un d'aquests materials que s'han desenvolupat recentment i que abasta les principals tecnologies avançades en el formigó: el Formigó de Molt Alt Rendiment Reforçat amb Fibres (UHPFRC). Aquest treball se centra específicament en els requisits fonamentals per al desenvolupament i l'ús generalitzat d'aquest, com ara la caracterització i classificació del comportament constitutiu a tracció. Aquest treball inclou una revisió profunda del comportament a tracció uniaxial del formigó i els seus canvis al temps que la tecnologia de les fibres ha evolucionat. A més, els mètodes tradicionals estàndard de caracterització, així com els recentment desenvolupats per al seu ús específic en l'UHPFRC són revisats i qüestionats. Al llarg del document, es mostra el desenvolupament de diferents metodologies per a determinar el comportament constitutiu a tracció uniaxial de l'UHPFRC, juntament amb una proposta de caracterització simplificada especialment desenvolupada per poder ser inclosa en normativa. Totes les metodologies desenvolupades presentades en aquest document han estat comprovades i validades. Aquests mètodes estan dissenyats específicament per a la seva aplicació en els resultats experimentals obtinguts a partir d'un tipus especial d'assaig de flexió a quatre punts, a més també s'inclou una proposta d'estandardització per a l'UHPFRC. Finalment, es presenta una proposta de classificació en funció dels paràmetres més rellevants del comportament a tracció de l'UHPFRC que són necessaris per al disseny i que es poden obtindre directament del mètode d'assaig estàndard suggerit per a la caracterització de l'UHPFRC. La classificació proposada té amb compte la classificació existent per al formigó armat convencional i el reforçat amb fibres. En ella, tant el formigó en massa com el formigó reforçat amb fibres es presenten com un cas particular d'una resposta constitutiva a tracció més general per al formigó. La metodologia estàndard i la classificació proposada estan d'acord amb l'evolució de formigó i unifica l / López Martínez, JÁ. (2017). CHARACTERISATION OF THE TENSILE BEHAVIOUR OF UHPFRC BY MEANS OF FOUR-POINT BENDING TESTS [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/79740 / TESIS