Etude de la transmission du signal sous irradiation transitoire dans les fibres optiques

Ce mémoire présente une étude sur la réponse des fibres optiques à une irradiation transitoire (impulsion X, ~1 MeV, doses 10-8 (10 puissance 8) rad s(exposant)-1). Des mesures complémentaires sous irradiation gamma continue ont aussi été accomplies(~1,2 MeV, doses 108 rad s-1). Additional measurements under steady-state gamma-ray have also been performed (~1,2 MeV,doses <=20 krad, dose rates ~0,5 rad s-1). Our study falls within the more general framework of the integration of optical fibers into the Laser Megajoule facility. The first chapter describes this framework together with the radiation induced defects in pure ordoped silica. The second chapter is focus on the experimental set-up used to measure the induced attenuation. We also give a sum up of the obtained measurements with pure-silica-core fibers and with fibers doped with germanium and/or phosphorus. The third chapter is dedicated to the analysis of the induced losses. The experimental spectra of radiation-induced attenuation have been decomposed with absorption bands related to absorbing defects generated. We have used an original method of decomposition based on the use of absorption bands previously identified in literature. Some physical mechanisms of defect generation and defect transformation have been suggestedST ETIENNE-Bib. électronique (422189901) / SudocSudocFranceF