Les modes de résonance acoustique dans les fibres optiques microstructurées - Applications aux capteurs répartis

Abstract : This thesis deals with the results of our study on the use of acoustic resonance modes to achieve distributed sensors based on photonic crystal fibres (Photonic Crystal Fibres : PCF). First, we demonstrated that at present it is difficult to measure backscattered transverse acoustic modes in an optical fibre. These modes whose frequency is below 2 GHz have been measured in a loop on a nonlinear PCF, a conventional fibre and a dispersion-shifted fibre. The different spectra show a dependence on the fibres cross section structure. Then we developed a Brillouin reflectometer (Brillouin Optical Time Domain Reflectometer : BOTDR) to monitor in real time the Brillouin spectrum along a fibre with a spatial resolution of about a dozen meters. It is particularly capable of discriminating between different modes present in the Brillouin spectrum. Comparison of spectrograms obtained on different transverse structures, confirms that the existence of Brillouin multipeak on PCF is linked to the very small core (with a diameter of about the wavelength of measurement) of the fibre. Finally, in order to better observe the distributed Brillouin spectrum, we have developed a vector Brillouin optical time domain analyzer for high-order acoustic modes to accurately map the Brillouin hybrid modes with the complementary phase of the spectrogram. The measurements taken on a PCF whose diameter varies linearly from 3.5 μm to 2.6 μm show a second Brillouin mode whose frequency varies as -118.2 MHz/ μm.
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Submitted on : Wednesday, August 10, 2011 - 12:41:47 PM
Last modification on : Tuesday, July 3, 2018 - 11:33:00 AM
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Michel Dossou. Les modes de résonance acoustique dans les fibres optiques microstructurées - Applications aux capteurs répartis. Physique [physics]. Université des Sciences et Technologie de Lille - Lille I, 2011. Français. ⟨tel-00614250⟩

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