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Etude de la diffusion Brillouin stimulée dans les fibres monomodes standard. Application aux capteurs de température et de pression

Abstract : Stimulated Brillouin scattering (SBS) is one of the effects one can observe in single-mode optical fibers and is of major interest in many applications. It results from the diffusion of laser waves through interaction with acoustical waves that are present in the medium and arises mainly threw the form of a backscattered Stokes wave, limiting the maximum power of a transmitted incident laser wave in a fiber and constituting a severe penalty for long distances of optical transmissions. The frequency shift of the Stokes wave with the laser wave is called Brillouin frequency and is closed to 11 GHz for a wavelength 1550 nm. The Stokes wave analysis allows the study of effects which modify acoustical properties, such as temperature and strain. That's why SBS is widely used for fiber optic sensing. In this present work, a general study of SBS properties in optical fibers is proposed, including a new expression for the pump threshold and an approximated solution for standard Brillouin equations. Starting from the pump-probe technique using a single laser source thanks to an electro-optic modulator, and consisting in the introduction of a counter-propagating artificial Stokes wave which is swept in frequency, the Brillouin gain curve is measured for temperatures ranging from 1K to ambiant temperature. This unique potentiality of Brillouin sensing at very low temperatures is shown with a resolution better than 1°C. Results with pressure show for the first time a linear relation with Brillouin frequency, so that SBS is a new sensor of pressure in optical fibers.
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Submitted on : Thursday, February 17, 2005 - 1:34:38 PM
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Sébastien Le Floch. Etude de la diffusion Brillouin stimulée dans les fibres monomodes standard. Application aux capteurs de température et de pression. Physique [physics]. Université de Bretagne occidentale - Brest, 2001. Français. ⟨tel-00008526⟩

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