This diploma thesis describes the function of commonly used elements among optical network, with an emphasis on fiber optic sensors. The basics of optical transmission and types of fibers are described, in addition to active and passive optical components, optical splitters and couplers. Optical fiber sensors are divided in two groups: intrinsic and extrinsic. Interferometric types of sensors are described in detail. The thesis compares theoretical assumptions and practical measurements of two serially-connected couplers. A~new module fulfilling real optical coupler function was made using Matlab. This module can be implemented into the VPIphotonics library. Finally, interferometric function of two serially-connected couplers was tested.

L'objectif de cette thèse est de développer un nouveau schéma numérique du type volumes finis pour la dynamique des gaz. Dans deux articles, F.Berthelin, T.Goudon et S.Minjeaud proposent de résoudre le système des équations d'Euler barotrope en dimension 1 d'espace, avec un schéma d'ordre 1 fonctionnant sur grilles décalées et dont la conception des flux est inspirée des schémas cinétiques. Nous proposons d'enrichir ce schéma afin qu'il puisse résoudre le système des équations d'Euler barotrope ou complet, en dimension 2 d'espace sur maillage cartésien ou non structuré, possiblement à l'ordre 2 et le cas échéant à bas nombres de Mach. Nous commencerons par développer une version 2D du schéma sur grilles cartésiennes (ou MAC) à l’ordre 2 via une méthode de type MUSCL, d'abord pour les équations barotropes puis pour les équations complètes. Ces dernières demandent de traiter une équation d’énergie supplémentaire et l’un des problèmes -résolu- est de trouver une définition discrète convenable de l’énergie totale telle qu'elle satisfasse une équation conservative locale. Dans un troisième chapitre nous étudierons le passage à la limite du compressible vers l'incompressible et nous verrons comment utiliser les atouts de notre schéma afin de le modifier et d'en faire un schéma Asymptotic Preserving pour des écoulements à bas nombres de Mach. Dans un quatrième temps nous proposerons une adaptation du schéma sur des maillages non structurés. Notre approche sera fortement inspirée des méthodes DDFV et pourra présenter des avantages dans les régimes à faibles nombres de Mach. Cette thèse se termine par un cinquième chapitre issu d’une collaboration lors du CEMRACS 2017, où le point de vue considéré n’est plus macroscopique mais microscopique. Nous commencerons par étudier un modèle micro/macro idéalisé auquel un processus stochastique a été ajouté puis nous tenterons d'en déduire un modèle à grande échelle pour un système fortement couplé, qui soit consistant avec la description micro/macro sous-jacente du problème physique. / The objective of this thesis is to develop a new numerical scheme of finite volume type for gas dynamics. In two articles, F.Berthelin, T.Goudon and S.Minjeaud propose to solve the barotropic Euler system in dimension 1 of space, with a first order scheme that works on staggered grids and of which fluxes are inspired by kinetic schemes. We propose to enhance this scheme so that it can solve the barotropic or complete Euler systems, in dimension 2 of space on Cartesian or unstructured grids, possibly at order 2 and at Low Mach numbers where appropriate. We begin with the development of a 2D version of the scheme on Cartesian (or MAC) grids, at order 2 via a MUSCL type method, for the barotropic equations at first and then for the complete equations. The latter require to handle with an additional energy equation and one of the -solved- problems is to find a suitable discrete definition of the total energy such that it satisfies a local conservative equation. In a third chapter we study the transition from the compressible case to the incompressible limit and we shall see how to use the advantages of our initial scheme in order to make it an Asymptotic Preserving scheme at low Mach numbers. In a fourth chapter we propose an adaptation of the scheme on unstructured meshes. Our approach is strongly inspired by the DDFV methods and may have advantages in low-Mach regimes.This thesis ends with a fifth chapter issued from a collaboration during CEMRACS 2017, where the considered point of view is no longer macroscopic but microscopic. We begin by studying a simplified micro/macro model with an added stochastic process and then we attempt to deduce a large-scale model for a strongly coupled system which has to be consistent with the underlying micro / macro description of the physical problem.

We have harnessed the power of various programmable photonics devices for an interferometric measurement technique. Distortion-free laser-based velocity measurements through a dynamic gas-liquid interface are enabled by a closed-loop optoelectronic system. We are employing electrically tunable lenses and micro mirrors to correct low-order wavefront distortions effectively. Our work represents a paradigm shift in interferometric velocity measurement techniques from using static to dynamic optical elements.

Cette thèse traite de la modélisation des tsunamis, des grandes échelles de propagation aux impacts sur desstructures côtières. Un inventaire des phénomènes physiques associés est établi et des modèles adéquats sontprésentés. Une étude numérique avec le modèle de Saint-Venant est effectuée avec le développement d’uneméthode de raffinement de maillage à seuil automatique. La simplicité et les performances de l’approche sontdémontrées. Pour améliorer la précision des prévisions, un système original approchant le modèle Serre-Green-Nahgdi est investigué. Une méthode pour prendre en compte la dissipation d’énergie au déferlement estproposée. Ce modèle permet d’envisager la modélisation fine de la propagation et de l’arrivée à la côte destsunamis dispersifs et non linéaires en des temps de calcul acceptables. Les différents types d’impact sur desstructures sont modélisés grâce à un modèle diphasique compressible permettant de considérer les écoulementsà phases séparées et les milieux aérés. Pour envisager une résolution à tous les régimes, des schémas TousMach sont investigués. Un schéma Tous Mach à variation totale limitée est proposé. Grâce à cette approche,des impacts incompressibles et compressibles sont investigués avec le même modèle. Les impactsd’écoulements aérés induisent des pressions moins élevées mais sur des temps plus longs que leurshomologues en phases pures. Bien que le schéma Tous Mach proposé soit moins sujet aux oscillationsnumériques que les préconditionnements classiques de la littérature, des oscillations non physiques à basnombre de Mach sont mises en évidence sur certains cas tests. Pour finir, une méthode de couplage entremodèles de propagation et d’impact est proposée, afin de pouvoir simuler un tsunami finement avec desmodèles appropriés à chacune de ces phases. / This thesis deals with tsunami modeling, from the large propagation scales to impacts on coastal structures. Aninventory of the associated physical phenomena is given and some adequat models are presented. A numericalstudy is carried out with the Saint-Venant model with the devellopment of an automatic refinment adaptivemesh method. The resolution efficiency and simplicity is justified. To increase the accuracy forecasts, anoriginal system which approximates the Serre-Green-Naghdi model is investigated. A breaking wave methodassociated with this model is proposed. This dissipative model allows thinking about accurate dispersive nonlinear tsunamis simulations up to the coast. Several wave impacts on stuctures are investigated with a generaltwo-phase model allowing separate phases as well as aerated impact studies. The all Mach regime numericaldifficulties are investigated. A new all Mach scheme with limited total variation bound is proposed. Thanks tothis approach, incompressible and compressible impacts are investigated with the same model. Aerated impactsare shown to give smaller impact pressure but on longer time than pure fluid impacts. In spite that the all Machscheme proposed reduces the numerical oscillations of classical literature preconditionning, some unphysicaloscillations are highlighted on some test cases. At the end, a coupling method is proposed in order to accuratlymodel the propagation and the impact of a tsunami with appropriated models for each phases.

This thesis addresses basic scientific research in the field of transmitter front-end circuits for electro-optical data communication. First, the theoretical fundamentals are presented and analyzed. Based on the theoretical considerations, conceptual circuit designs are studied. Finally, in order to prove the described concepts, the circuits were experimentally characterized and subsequently compared to other works in the literature. The analysis covers key theoretical aspects regarding transmitter front-end circuits. It starts from the basic physical effects inside a transistor and ends with the design of high-swing modulator drivers. Furthermore, it comprises the fundamentals of optical modulators as well as the integration of the electrical driver with the modulator. First, the concept of a basic monolithically integrated transmitter consisting of a Mach-Zehnder modulator (MZM) and an electrical driver is presented. The circuit reaches a bit-error-free data rate of 37 Gb/s, which is a record among other monolithically integrated transmitters reported in the literature. It was shown that by employing a high-swing driver, high extinction ratios (ER) can be achieved (namely 8.4 dB at 25 Gb/s and 7.6 dB at 35 Gb/s) while using short-length phase shifters (2 mm of length). It was therefore proved that one of the main drawbacks of the MZM-based transmitters, namely their large chip area, can be mitigated by using high-swing drivers, however without sacrificing the ER. Next, an improved modulator driver design is investigated, the focus of the study being the linearity. In addition to a high peak-to-peak differential output voltage swing of 7.2 Vpp,d, the driver achieves record-low total harmonic distortion (THD) values of 1% (at 1 GHz, for the output swing of 6.5 Vpp,d) and 1.7% (at 1 GHz, for the output swing of 7 Vpp,d). Moreover, the driver reaches a bandwidth of 61.2 GHz and shows a high power efficiency when relating its DC power consumption to its output voltage swing. The achievement of a high linearity and bandwidth without an increased power consumption is due to the fact that the bias currents of the emitter-follower (EF) stages are provided by means of resistors instead of the conventional current sources. The two approaches were first analyzed mathematically and subsequently compared by means of circuit simulations. It was shown that the proposed approach for the realization of the EFs – i.e. by means of resistors – allows a reduction of the DC power consumption by 19% compared to the current-source approach for an equivalent performance in terms of linearity and bandwidth. Finally, a modulator driver concept suitable for higher-order modulation formats is studied, namely the 8-level pulse amplitude modulation (PAM-8). The circuit was realized as a 3-bit digital-to-analog converter (DAC), thus being able to yield 8-level output signals. Moreover, the circuit is able to function as a PAM-4 driver as well, thanks to the tunable tail currents of the DAC core. It achieves a symbol rate of 50 Gbaud, which corresponds to a bit rate of 150 Gb/s for the PAM-8 modulation and 100 Gb/s for PAM-4. The study showed that a modulator driver can be realized that is able to switch between different modulation formats (namely PAM-8 and PAM-4), without requiring extra power or additional circuit parts. Moreover, the use of on-chip single-to-differential converters (SDCs) targets the relaxation of the requirements on the stages that precede the driver. Finally, relating its DC power consumption (590 mW, including the SDCs) to its output voltage swing (4 Vpp,d), the driver shows one of the highest power efficiencies among PAM modulator drivers in the literature.

The purpose of this thesis is the theoretical study of interference and correlation effects in multimode and continuum mode quantum systems. We are concerned with interference effects in multiport devices which in a sense are generalised Mach-Zehnder interferometers. It is shown how these multimode devices can be employed for the study of negative result and interaction free measurements. Interference and coherence effects are also studied in relation to the radiation fields generated by atoms through the process of spontaneous emission. Besides first order interference, higher order coherence effects are investigated with the aid of Glauber's photodetection theory and it is found that detectors that lie in spacelike regions may display nonclassical correlations under certain conditions. It is well known that the vanishing of field commutators between regions that cannot be connected by subluminal signals reflects the locality of quantum field theory. But is it possible that these spacelike regions exhibit correlations that violate Bell type inequalities? This is the main question and principal concern of the thesis and the answer is affirmative, nonclassical correlations between spacelike regions are indeed possible. A scheme of four detectors that lie in spacelike points was also studied. In this case we do not consider the radiation field but a free scalar field in vacuum state. Nevertheless the virtual quanta of this field may induce nonclassical correlations if the intervals between the detectors are spacelike but small enough. The fundamental reason for this fact is the nonvanishing of the Feynman propagator outside the light cone. Since this propagator is decaying expotentially with the distance it is demonstrated that for large spacelike intervals field correlations obey classical inequalities. We should also note that different inertial observers will agree on the violation or not of these inequalities since the results are manifestly Lorentz invariant.

No description available.

Lors de la phase de rentrée atmosphérique d'une sonde spatiale, la paroi du corps est le siège de phénomènes physico-chimiques complexes. Nous nous intéressons dans cette thèse au cas où le matériau solide de l'objet de vol comporte plusieurs constituants s'ablatant de façon différentielle. En particulier, l'un de ces constituants subit un changement de phase donnant lieu à l'apparition d'une phase liquide. Nous sommes en présence de trois phases : solide, liquide et gaz. Les travaux effectués dans cette thèse correspondent au développement de méthodes numériques en 2D capables de modéliser les différentes interfaces en présence ainsi que l'évolution des fluides ou des matériaux séparés par celle-ci. L'enjeu principal de la thèse est de proposer des méthodes et des algorithmes de couplage pour l'écoulement diphasique, la thermique multimatériaux et les changements de phase (fusion et sublimation)

This thesis describes the development of a Mach-Zehnder interferometric filter based planar Doppler velocimetry (MZI-PDV) flow measurement technique. The technique uses an entirely new optical system, an unbalanced MZI incorporating glass blocks for wavefront-matching, to replace the iodine cell currently used in conventional PDV. The free spectral range of the interferometric filter can be selected by adjusting the optical path difference of the MZI. This allows the velocity measurement range, sensitivity and resolution to be varied. This system offers no restricts to the choice of laser wavelength of operation which is not the case with most techniques. Two techniques to process the interference fringe images are presented. The first uses the shift of the fringe pattern to determine the Doppler frequency shift along profiles. The second provides a full-field measurement by normalising the received light intensity at each pixel in the image. With the single camera MZI-PDV scheme, exact alignment of the two output images on the active area of the camera is automatic. This eliminates the pixel-matching problem in conventional two camera PDV systems. The technique allows the measurement of up to three components of the flow velocity across a plane defined by a laser light sheet. The construction of a single velocity component MZI-PDV system that incorporates a phase-locking system designed to stabilise the filter is described. Measurements are made on the velocity field of a rotating disc with maximum velocities of ~±70ms-1 and an axis-symmetric air jet (with a nozzle diameter of 20mm) with an exit velocity of ~85ms-1. Standard deviations in the measured velocities were found to be about 2.9 and 2ms-1 for the two processing methods respectively. The system was then modified to make 3-component velocity measurements using imaging fibre bundles to port multiple views to a single detector head, and the standard deviation of the velocity error is around ±3ms-1 for a maximum velocity of ~±30ms-1 in the field of view. The factors that will affect the quality of the interference fringe image are investigated including polarisation sensitivity of the two beam splitters and flatness of the optical components. The inclination angle and the optical path deviation have little effect on the contrast of the interference fringes since collimated light beams, rather than divergent ones, are used in the interferometer.

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