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RESEARCH PRODUCT

Ondes scélérates et statistiques extrêmes dans les systèmes optiques fibrés

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This thesis deals with extremes statistics which has become an attractive subject in optics since a comparison with oceanic rogue waves has been proposed at the end of 2007. We report some potential mechanisms stimulating the rogue wave formation in the context of guided propagation of light in optical fibers. In a first part, we explore optical rogue waves in supercontinuums generated by fourth-order modulation instability and we propose a stabilization method based on the use of two continuous seeds. Then, we present a detailed study on Raman fiber amplifiers where we determine the conditions of emergence of giant structures : in presence of a partially incoherent pumping wave, a quasi-instantaneous gain combined with a low walk-off lead to extremes statistics. We have validated these conditions for a continuous wave as well as a pulse train. Conclusions have also been successfully extended to a parametric amplifier based on incoherent second-order modulation instability. In the last part, a turbulent system is studied as a function of incoherence and we identify three regimes. In one of these regimes, we highlight the existence of intermittent quasi-solitons. Finally, we are interested in nonlinear structures called Akhmediev Breathers which present compression-decompression cycles and we focus our attention on its asymptotic limit: the Peregrine soliton. It corresponds to a very interesting prototype of rogue waves. Our experimental work, performed at optical communication wavelength and using several methods of spectro-temporal characterization, is complemented by numerical and analytical studies.