General analytical model for distributed Brillouin sensors with sub-meter spatial resolution

Luc Thévenaz
SPIE, 2009
Article de conférence

A general analytic solution for Brillouin distributed fibre sensors with sub-meter spatial resolution has been obtained by solving the coupled wave equation by a perturbation method. The effect of the interaction of a square pump pulse with a continuous signal is described in full generality for all possible pumping schemes and for any detuning with the resonance condition of the Brillouin interaction. The model predicts how the acoustic wave, the signal amplitude and the gain spectral profile depend upon the pumping scheme. The analytical solution is an unprecedented tool to optimize the sensor configuration by determining the optimum pumping scheme.

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Luc Thévenaz
SPIE, 2009
Article de conférence

Résumé

Official source

https://infoscience.epfl.ch/record/143474?ln=fr

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Concepts associés (13)

Concepts associés

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Publications associées (5)

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Diffusion Brillouin

La 'diffusion Brillouin' est la diffusion inélastique de la lumière par les ondes acoustiques d'un milieu. Dans une expérience de diffusion Brillouin, on illumine un milieu à l'aide d'un faisceau las

Fibre optique

Une fibre optique est un fil dont l’âme, très fine et faite de verre ou de plastique, a la propriété de conduire la lumière et sert pour la fibroscopie, l'éclairage ou la transmission de données num

Acoustic wave

Acoustic waves are a type of energy propagation through a medium by means of adiabatic loading and unloading. Important quantities for describing acoustic waves are acoustic pressure, particle velocit

Distributed Brillouin sensing with sub-meter spatial resolution: modeling and processing

Stella Foaleng Mafang, Luc Thévenaz

A general analytic solution for Brillouin distributed sensing in optical fibers with sub-meter spatial resolution is obtained by solving the acoustical-optical coupled wave equations by a perturbation method. The Brillouin interaction of a triad of square pump pulses with a continuous signal is described, covering a wide range of pumping schemes. The model predicts how the acoustic wave, the signal amplitude and the optical gain spectral profile depend upon the pumping scheme. Sub-meter spatial resolution is demonstrated for bright-, dark- and pi-shifted interrogating pump pulses, together with disturbing echo effects, and the results compare favorably with experimental data. This analytic solution is an excellent tool not only for optimizing the pumping scheme but also for post-processing the measured data to remove resolution degrading features.

Optical Society of America2011

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Recent progress towards centimetric spatial resolution in distributed fibre sensing

Sang Hoon Chin, Stella Foaleng Mafang, Nikolay Primerov, Kwang-Yong Song, Luc Thévenaz

Optical fibre sensors based on stimulated Brillouin scattering have now clearly demonstrated their excellent capability for long-range distributed strain and temperature measurements. The fibre is used as sensing element and a value for temperature and/or strain can be obtained from any point along the fibre. While classical configurations have practically a spatial resolution limited by the phonon lifetime to 1 meter, novel approaches have been demonstrated these past years that can overcome this limit. This can be achieved either by the prior activation of the acoustic wave by a long lasting pre-pumping signal, leading to the optimized configuration using Brillouin echoes, or by probing a classically generated steady acoustic wave using a ultra-short pulse propagating in the orthogonal polarization of a highly birefringent fibre. These novel configurations can offer spatial resolutions in the centimetre range, while preserving the full accuracy on the determination of temperature and strain.

The International Society for Optical Engineering2010

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Sub-centimetre Spatial Resolution in Distributed Fibre Sensing, based on Dynamic Brillouin Grating in Optical Fibers

Sang Hoon Chin, Nikolay Primerov, Luc Thévenaz

Optical fibre sensors based on stimulated Brillouin scattering in optical fibers have now clearly demonstrated their excellent capability for long-range distributed strain and temperature measurements. The fibre is used as sensing element and a value for temperature and/or strain can be obtained from any point along the fibre. While the spatial resolution of classical configurations is practically limited to 1 meter by the phonon lifetime, novel approaches have been demonstrated these past years that can overcome this limit. In this paper, this could be achieved by two physical processes: prior activation of a steady acoustic wave through the classical Brillouin interaction between two Brillouin pumps, and interrogation by Bragg reflection on the acoustic wave using a distinct ultra-short pulse in a highly birefringent fiber.We could achieve a spatial resolution below one centimetre, while preserving the full accuracy on the determination of temperature and strain.

2012

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