Two-dimensional FEM Analysis of Brillouin Gain Spectra in Acoustic Guiding and Antiguiding Single Mode Optical Fibers

The analysis of optical and acoustic properties of optical fibers is required for accurate Brillouin gain spectrum (BGS) determination. We present a full modal-analysis of the guided optical and acoustic modes based on a two-dimensional finite-element method (2D-FEM) for BGS calculation using COMSOL Multiphysics. We believe that this method will be helpful in analyzing and designing special fibers for applications, such as fiber amplifiers with significant SBS (Stimulated Brillouin Scattering) suppression or Brillouin-based fibersensors. The model is adapted for BGS evaluation of any single mode fiber (in term of optical mode) based on its profile, namely its geometry, and its doping composition. Compared to standard multi-layer methods limited to axially-symmetric fibers [1], the 2D-FEM analysis enables the BGS computation even for more complicated geometries, such as PANDA polarization-maintaining fiber where the optical index and the material stress are azimuthally dependant. The results of numerical modeling have shown good agreement with measured Brillouin spectra for different types of silica fibers. Examples are given for a standard GeO2-doped core fiber (standard fiber for telecommunication applications), Fluor-doped cladding fiber (acoustic anti-waveguide) and PANDA fiber

UV irradiation influence on stimulated Brillouin scattering in photosensitive optical fibres

International audienceA study on the influence of UV radiation on stimulated Brillouin scattering in photosensitive germanosilicate optical fibres is presented. The UV exposure of a highly germanium-doped fibre was performed at a power density of ~142 W/cm2. In this configuration, a refractive index change of about 2.5×10−3 was measured, partially due to the compaction phenomenon as well as a 20 MHz permanent change in the Brillouin frequency shift (at 1.55 µm)

PRISE EN COMPTE DU PROFIL DE DOPAGE POUR L'ANALYSE MODALE DES SPECTRES BRILLOUIN DE FIBRES OPTIQUES MONOMODES

National audienceLes caractéristiques spectrales de la diffusion Brillouin spontanée dans les fibres optiques sont fortement dépendantes du profil de composition chimique. Les profils Brillouin des guides acoustiques (ondes acoustiques guidées dans le coeur) et des anti-guides acoustiques (ondes acoustiques guidées dans la gaine) sont très différents. Cet article présente une analyse 2D par une méthode à éléments finis des modes acoustiques en vue de la détermination du spectre de gain Brillouin. Le modèle a été validé expérimentalement dans le cas d'une fibre à coeur dopé Germanium (cas de guides acoustiques) et ensuite appliqué au cas des fibres à gaine enterrée par dopage Fluor (cas d'anti-guides acoustiques)

Two-dimensional FEM analysis of Brillouin gain spectra in acoustic guiding and acoustic antiguiding single mode optical fibers

The analysis of optical and acoustic properties of optical fibers is required for accurate Brillouin gain spectrum (BGS) determination. We present a full modal-analysis of the guided optical and acoustic modes based on a two-dimensional finite-element method (2D-FEM) for BGS calculation using COMSOL Multiphysics. We believe that this method will be helpful in analyzing and designing special fibers for applications, such as fiber amplifiers with significant SBS (Stimulated Brillouin Scattering) suppression or Brillouin-based fiber sensors. The model is adapted for BGS evaluation of any single mode fiber (in term of optical mode) based on its profile, namely its geometry, and its doping composition. Compared to standard multi-layer methods limited to axially-symmetric fibers [1], the 2D-FEM analysis enables the BGS computation even for more complicated geometries, such as PANDA polarization-maintaining fiber where the optical index and the material stress are azimuthally dependant. The results of numerical modeling have shown good agreement with measured Brillouin spectra for different types of silica fibers. Examples are given for a standard GeO2-doped core fiber (standard fiber for telecommunication applications), Fluor-doped cladding fiber (acoustic anti-waveguide) and PANDA fiber

Two-dimensional FEM analysis of Brillouin gain spectra in acoustic guiding and acoustic antiguiding single mode optical fibers

The analysis of optical and acoustic properties of optical fibers is required for accurate Brillouin gain spectrum (BGS) determination. We present a full modal-analysis of the guided optical and acoustic modes based on a two-dimensional finite-element method (2D-FEM) for BGS calculation using COMSOL Multiphysics. We believe that this method will be helpful in analyzing and designing special fibers for applications, such as fiber amplifiers with significant SBS (Stimulated Brillouin Scattering) suppression or Brillouin-based fiber sensors. The model is adapted for BGS evaluation of any single mode fiber (in term of optical mode) based on its profile, namely its geometry, and its doping composition. Compared to standard multi-layer methods limited to axially-symmetric fibers [1], the 2D-FEM analysis enables the BGS computation even for more complicated geometries, such as PANDA polarization-maintaining fiber where the optical index and the material stress are azimuthally dependant. The results of numerical modeling have shown good agreement with measured Brillouin spectra for different types of silica fibers. Examples are given for a standard GeO2-doped core fiber (standard fiber for telecommunication applications), Fluor-doped cladding fiber (acoustic anti-waveguide) and PANDA fiber

In situ radiation influence on strain measurement performance of Brillouin sensors

International audienceA new approach is proposed to monitor in situ the influence of gamma radiations on Brillouin properties of optical fiber extensometers. Experimental results are illustrated with the characterization of two fibers samples up to total dose of about 600Gy. The Brillouin frequency shift remains unaffected at such radiations level, as well as the spectral Brillouin signature or its dependence with strain. Meanwhile, propagation losses increase under radiations with an amplitude related to fiber dopants. The target application is nuclear wastes repository monitoring where higher doses are expected. UV radiation preliminary tests show that compaction phenomenon may occur at such high doses, inducing Brillouin frequency shift up to 20 MHz