Search results for "Non linéaire"
showing 5 items of 25 documents
Microfibres for nonlinear optics
2011
In this thesis, I present my works on the fabrication, the characterization and the use of optical microfibres. Microfibres are optical fibres drawn down to sub-wavelength diameters by a temperature controlled process. Due to their small dimensions, microfibers have very special properties such as a high confinement of the electromagnetic field, a enhanced non-linear coefficient and a large evanescent tail. These properties are studied in the first chapter, after which a description of the techniques used for the drawing and manipulation of the microfibres is given. Next, we present our experiments on non-linear effects in silica microfibres. In particular, we show that it is possible to ge…
Observateur et contrôle optimal : améliorer l'efficacité de la conduite automobile avec Kalman et Pontryagin
2010
The PhD presents a combined approach to improving individual car efficiency. An optimal observer, the Extended Kalman Filter, is used to create an efficiency model for the car. Particular attention was paid to handling the asynchronous and redundant nature of the measurement data. A low-cost sensor suite developed to measure data is described. This sensor suite was installed on multiple vehicles to good success. It employsan accelerometer, gps, fuel injector timer, and Vss input to measure all the data necessary to reconstruct the car's state. This observer and sensor suite can be used as the base for any study which requires car efficiency maps, allowing research to proceed without manufac…
Etude des sources supercontinuum à fibres transparentes dans le moyen infrarouge
2012
The work reported in this thesis deals with the study of the supercontinuum generation in fibers transparent in the mid-infrared. To generate a supercontinuum between 3 and 5 µm we compare different glass families such as fluoride glasses, tellurite glasses and chalcogenide glasses. These fibers are pumped with fiber lasers emitting at 2 µm with nanosecond or picosecond pulse duration. This wavelength allows us to reach the zero dispersion wavelength of the chalcogenide tapered fibers. We report supercontinuum generation up to 3800 nm in a fluoride glass fiber. A connection with 75 % of transmission is made between a ZBLAN and a SiO2 fiber. We also measured absorption lines of the methane a…
Nouveaux systèmes de contrôle de la polarisation de la lumière par effets non lineaires dans les fibres optiques
2013
This thesis deals with the work the development of an all-optical device for the control of the polarization state of light. Actually, this feature of light remains so far an uncontrolled variable, which can degrade the performances of all-optical systems. Based on nonlinear interaction between two counterpropagating waves inside an optical fiber, this device called polarization attractor allows to control the polarization state of light without polarization dependent losses.In a first part, we carry out extensive studies of the polarization attractor properties leading to the control and the regeneration of the polarization state of the 10-Gb/s NRZ and RZ telecommunication signals. Then, t…
Nonlinear resonances and some of their applications to information processing
2021
The study of resonance phenomena in nonlinear dynamical systems has drawn considerable attention for years. The most studied nonlinear resonance is undoubtedly the famous stochastic resonance, which consists of perturbing a nonlinear system with an appropriate amount of noise to enhance the detection of a subthreshold input signal. Since the introduction of stochastic resonance in the context of climate dynamics, it was later observed that a deterministic high frequency perturbation can replace noise leading to vibrational resonance. Even if this latter resonance was investigated in many areas of science for more than two decades now, it is still receiving attentions. It is the subject of t…