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Timeline of Sylvie Delepine-Lesoille

2017
Jun
13
Published new article




Article

France’s State of the Art Distributed Optical Fibre Sensors Qualified for the Monitoring of the French Underground Repos...

Published: 13 June 2017 by MDPI in Sensors

doi: 10.3390/s17061377

This paper presents the state of the art distributed sensing systems, based on optical fibres, developed and qualified for the French Cigéo project, the underground repository for high level and intermediate level long-lived radioactive wastes. Four main parameters, namely strain, temperature, radiation and hydrogen concentration are currently investigated by optical fibre sensors, as well as the tolerances of selected technologies to the unique constraints of the Cigéo’s severe environment. Using fluorine-doped silica optical fibre surrounded by a carbon layer and polyimide coating, it is possible to exploit its Raman, Brillouin and Rayleigh scattering signatures to achieve the distributed sensing of the temperature and the strain inside the repository cells of radioactive wastes. Regarding the dose measurement, promising solutions are proposed based on Radiation Induced Attenuation (RIA) responses of sensitive fibres such as the P-doped ones. While for hydrogen measurements, the potential of specialty optical fibres with Pd particles embedded in their silica matrix is currently studied for this gas monitoring through its impact on the fibre Brillouin signature evolution.

0 Reads | 1 Citations
2017
Feb
17
Published new article




Article

Steady γ-Ray Effects on the Performance of PPP-BOTDA and TW-COTDR Fiber Sensing

Published: 17 February 2017 by MDPI in Sensors

doi: 10.3390/s17020396

We investigated the evolution of the performances of Pulse Pre Pump-Brillouin Time Domain Analysis (PPP-BOTDA) and Tunable Wavelength Coherent Optical Time Domain Reflectometry (TW-COTDR) fiber-based temperature and strain sensors when the sensing optical fiber is exposed to two γ-ray irradiation conditions: (i) at room temperature and a dose rate of 370 Gy(SiO2)/h up to a total ionizing dose (TID) of 56 kGy; (ii) at room temperature and a dose rate of 25 kGy(SiO2)/h up to a TID of 10 MGy. Two main different classes of single-mode optical fibers have been tested in situ, radiation-tolerant ones: fluorine-doped or nitrogen-doped core fibers, as well as Telecom-grade germanosilicate ones. Brillouin and Rayleigh Sensitivities of N-Doped fibers were not reported yet, and these characterizations pave the way for a novel and alternative sensing scheme. Moreover, in these harsh conditions, our results showed that the main parameter affecting the sensor sensitivity remains the Radiation Induced Attenuation (RIA) at its operation wavelength of 1550 nm. RIA limits the maximal sensing range but does not influence the measurement uncertainty. F-doped fiber is the most tolerant against RIA with induced losses below 8 dB/km after a 56 kGy accumulated dose whereas the excess losses of other fibers exceed 22 dB/km. Both Rayleigh and Brillouin signatures that are exploited by the PPP-BOTDA and the TW-COTDR remain unchanged (within our experimental uncertainties). The strain and temperature coefficients of the various fibers under test are not modified by radiations, at these dose/dose rate levels. Consequently, this enables the design of a robust strain and temperature sensing architecture for the monitoring of radioactive waste disposals.

1 Reads | 3 Citations
2016
Apr
18
Published new article




Article

Error Analysis of Clay-Rock Water Content Estimation with Broadband High-Frequency Electromagnetic Sensors—Air Gap Effec...

Published: 18 April 2016 by MDPI in Sensors

doi: 10.3390/s16040554

Broadband electromagnetic frequency or time domain sensor techniques present high potential for quantitative water content monitoring in porous media. Prior to in situ application, the impact of the relationship between the broadband electromagnetic properties of the porous material (clay-rock) and the water content on the frequency or time domain sensor response is required. For this purpose, dielectric properties of intact clay rock samples experimental determined in the frequency range from 1 MHz to 10 GHz were used as input data in 3-D numerical frequency domain finite element field calculations to model the one port broadband frequency or time domain transfer function for a three rods based sensor embedded in the clay-rock. The sensor response in terms of the reflection factor was analyzed in time domain with classical travel time analysis in combination with an empirical model according to Topp equation, as well as the theoretical Lichtenecker and Rother model (LRM) to estimate the volumetric water content. The mixture equation considering the appropriate porosity of the investigated material provide a practical and efficient approach for water content estimation based on classical travel time analysis with the onset-method. The inflection method is not recommended for water content estimation in electrical dispersive and absorptive material. Moreover, the results clearly indicate that effects due to coupling of the sensor to the material cannot be neglected. Coupling problems caused by an air gap lead to dramatic effects on water content estimation, even for submillimeter gaps. Thus, the quantitative determination of the in situ water content requires careful sensor installation in order to reach a perfect probe clay rock coupling.

1 Reads | 1 Citations
2015
Oct
15
Published new article




Article

Fabrication of optical fibers with palladium metallic particles embedded into the silica cladding

Published: 15 October 2015 by The Optical Society in Optical Materials Express

doi: 10.1364/ome.5.002578

Absorption of hydrogen gas (H2) in contact with palladium (Pd) makes Pd a material of choice for numerous H2 sensors. In this paper, we present the fabrication of optical fibers with embedded Pd particles in the silica cladding of the fibers. Fiber preforms prepared with a powder mixture of silica and palladium oxide (PdO) are heat-treated under specific conditions to reduce PdO to metallic Pd particles, dispersed in the silica matrix. Optical fibers with different topologies have been fabricated with lengths of several hundred meters and PdO concentration ranging from 0.01% to 5% mol (in addition to silica). Oxidation state, homogeneity, shape and size distribution of the particles embedded in the cladding of the preform and the fiber samples are studied with structural and micro-structural characterizations. Optical properties of the fibers are finally studied for evaluating the potential of this proof-of-concept work.

0 Reads | 1 Citations
2015
Sep
28
Published new article






Study of the hydrogen influence on the acoustic velocity of single-mode fibers by Rayleigh and Brillouin backscattering ...

Published: 28 September 2015 by SPIE-Intl Soc Optical Eng in 24th International Conference on Optical Fibre Sensors

doi: 10.1117/12.2194102

We study the effect of hydrogen gas diffusion in silica optical fibers on Brillouin and Rayleigh scatterings. By modeling hydrogen diffusion kinetics as a function of temperature and pressure and by measuring simultaneously Rayleigh and Brillouin scattering on G652 single-mode fiber samples during H2 desorption (previously exposed to 175 bars H2 at 80°C), we have demonstrated experimentally that acoustic velocity increases linearly with H2 concentration with a ratio of about (4.8 m/s) / (%mol H2). © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

1 Reads | 0 Citations
2015
Jun
15
Published new article




Article

Effects of Radiation and Hydrogen-Loading on the Performances of Raman Distributed Temperature Fiber Sensors

Published: 15 June 2015 by Institute of Electrical and Electronics Engineers (IEEE) in Journal of Lightwave Technology

doi: 10.1109/jlt.2014.2388453

The integration of Raman-distributed temperature fiber-based sensors (RDTS) into the envisioned French deep geological repository for nuclear wastes, called Cigéo requires evaluating how the performances of RDTS evolve in harsh environments, more precisely in presence of H2 or γ-rays. Both H 2 and radiations are shown to affect the temperature measurements made with the single-ended RDTS technology. The amplitudes of the observed effects depend on the different classes of multimode fibers varying in terms of composition and coatings. By selecting the most tolerant fiber structure for the sensing, we could maintain the RDTS performances for such application. A hardening by system studies will be mandatory before integration of single-ended RDTS in Cigéo.

0 Reads | 5 Citations
2014
May
02
Published new article






Palladium particles embedded into silica optical fibers for hydrogen gas detection

Published: 02 May 2014 by SPIE-Intl Soc Optical Eng in SPIE Photonics Europe

doi: 10.1117/12.2054303

In this paper, we report the fabrication and characterization of a new concept of optical fibers whose cladding is composed of palladium particles embedded into the silica glass cladding. Since conventional fiber processes are not suitable for such realizations, we developed an original process based on powder technology to prepare our specific preforms. Step, graded index and photonic crystal optical fibers with original shapes were realized. The use of high purity powders as raw materials combined to a specific preforms heat treatment allowed the fabrication of resistant and long length metal-cladding optical fibers. Microstructured Pd-SiO2 composite cladding optical fibers with single-mode behavior and optical losses lower than 2 dB/m at 1530 nm were characterized. Hydrogen-induced attenuation sensitivity of these fibers at the 1245 nm wavelength was demonstrated after long H2 exposure. Dehydrogenation kinetics calculations and experiments were studied. © (2014) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

0 Reads | 0 Citations
2013
Sep
16
Published new article




Article

Dielectric relaxation behavior of Callovo-Oxfordian clay rock: A hydraulic-mechanical-electromagnetic coupling approach

Published: 16 September 2013 by Wiley in Journal of Geophysical Research: Solid Earth

doi: 10.1002/jgrb.50343

[1] Water content is a key parameter to monitor in nuclear waste repositories such as the planed underground repository in Bure, France, in the Callovo‐Oxfordian (COx) clay formation. High‐frequency electromagnetic (HF‐EM) measurement techniques, i.e., time or frequency domain reflectometry, offer useful tools for quantitative estimation of water content in porous media. However, despite the efficiency of HF‐EM methods, the relationship between water content and dielectric material properties needs to be characterized. Moreover, the high amount of swelling clay in the COx clay leads to dielectric relaxation effects which induce strong dispersion coupled with high absorption of EM waves. Against this background, the dielectric relaxation behavior of the clay rock was studied at frequencies from 1 MHz to 10 GHz with network analyzer technique in combination with coaxial transmission line cells. For this purpose, undisturbed and disturbed clay rock samples were conditioned to achieve a water saturation range from 0.16 to nearly saturation. The relaxation behavior was quantified based on a generalized fractional relaxation model under consideration of an apparent direct current conductivity assuming three relaxation processes: a high‐frequency water process and two interface processes which are related to interactions between the aqueous pore solution and mineral particles (adsorbed/hydrated water relaxation, counter ion relaxation and Maxwell‐Wagner effects). The frequency‐dependent HF‐EM properties were further modeled based on a novel hydraulic‐mechanical‐electromagnetic coupling approach developed for soils. The results show the potential of HF‐EM techniques for quantitative monitoring of the hydraulic state in underground repositories in clay formations.

0 Reads | 5 Citations
2013
Jun
30
Published new article




Article

Durcissement des capteurs à fibre optique fondés sur la rétrodiffusion Brillouin. Application à l’observation - surveill...

Published: 30 June 2013 by Lavoisier in Instrumentation Mesure Métrologie

doi: 10.3166/i2m.13.1-2.69-96

0 Reads | 0 Citations
2013
May
20
Published new article






Validation of TW-COTDR method for 25km distributed optical fiber sensing

Published: 20 May 2013 by SPIE-Intl Soc Optical Eng in Fifth European Workshop on Optical Fibre Sensors

doi: 10.1117/12.2025802

The paper reports results of the long distance (25 km range) distributed optical fiber sensing by means of Tunable Wavelength Coherent Optical Time Domain Reflectometry (TW-COTDR) method. The tests were designed to verify the accuracy and repeatability of the method in long distance measurements, as well as compatibility with various optical fiber types. Results demonstrate the capability of the method to detect strain or temperature changes over long distances. This proposed method is compared to Brillouin sensing techniques, into the same fibers. Unlike the Brillouin-based methods, measurement uncertainty does not increase with increasing distance. We demonstrated 0.16°C uncertainty at 21km.

0 Reads | 0 Citations
2012
Nov
19
Published new article




Article

High γ-ray dose radiation effects on the performances of Brillouin scattering based optical fiber sensors.

Published: 19 November 2012 in Optics Express

doi:

The use of distributed strain and temperature in optical fiber sensors based on Brillouin scattering for the monitoring of nuclear waste repository requires investigation of their performance changes under irradiation. For this purpose, we irradiated various fiber types at high gamma doses which represented the harsh environment constraints associated with the considered application. Radiation leads to two phenomena impacting the Brillouin scattering: 1) decreasing in the fiber linear transmission through the radiation-induced attenuation (RIA) phenomenon which impacts distance range and 2) modifying the Brillouin scattering properties, both intrinsic frequency position of Brillouin loss and its dependence on strain and temperature. We then examined the dose dependence of these radiation-induced changes in the 1 to 10 MGy dose range, showing that the responses strongly depend on the fiber composition. We characterized the radiation effects on strain and temperature coefficients, dependencies of the Brillouin frequency, providing evidence for a strong robustness of these intrinsic properties against radiations. From our results, Fluorine-doped fibers appear to be very promising candidates for temperature and strain sensing through Brillouin-based sensors in high gamma-ray dose radiative environments.

0 Reads | 2 Citations
2012
Nov
15
Published new article




Article

High γ-ray dose radiation effects on the performances of Brillouin scattering based optical fiber sensors

Published: 15 November 2012 by The Optical Society in Optics Express

doi: 10.1364/oe.20.026978

The use of distributed strain and temperature in optical fiber sensors based on Brillouin scattering for the monitoring of nuclear waste repository requires investigation of their performance changes under irradiation. For this purpose, we irradiated various fiber types at high gamma doses which represented the harsh environment constraints associated with the considered application. Radiation leads to two phenomena impacting the Brillouin scattering: 1) decreasing in the fiber linear transmission through the radiation-induced attenuation (RIA) phenomenon which impacts distance range and 2) modifying the Brillouin scattering properties, both intrinsic frequency position of Brillouin loss and its dependence on strain and temperature. We then examined the dose dependence of these radiation-induced changes in the 1 to 10 MGy dose range, showing that the responses strongly depend on the fiber composition. We characterized the radiation effects on strain and temperature coefficients, dependencies of the Brillouin frequency, providing evidence for a strong robustness of these intrinsic properties against radiations. From our results, Fluorine-doped fibers appear to be very promising candidates for temperature and strain sensing through Brillouin-based sensors in high gamma-ray dose radiative environments.

0 Reads | 11 Citations
2012
Sep
01
Published new article




Article

Distributed Hydrogen Sensing With Brillouin Scattering in Optical Fibers

Published: 01 September 2012 by Institute of Electrical and Electronics Engineers (IEEE) in IEEE Photonics Technology Letters

doi: 10.1109/LPT.2012.2206578

We report on the design and test of a truly distributed hydrogen sensor based on Brillouin scattering into single-mode G652 optical fibers. The proposed system enables remote, robust, long-term, and truly distributed hydrogen sensing into long-range structures, such as radioactive waste repositories, with a spatial resolution in the order of 2 m over several hundred meters. For the first time, we demonstrate that Brillouin frequency shift depends on hydrogen concentration in the silica core with a rate of approximately 0.21 MHz/%H2 . Influence parameters are discussed. We showed that temperature influence may be corrected with a collocated carbon-coated fiber.

0 Reads | 5 Citations
2010
Jan
01
Published new article




Article

Truly Distributed Optical Fiber Sensors for Structural Health Monitoring: From the Telecommunication Optical Fiber Drawl...

Published: 01 January 2010 by Hindawi Limited in Advances in Civil Engineering

doi: 10.1155/2010/930796

Although optical fiber sensors have been developed for 30 years, there is a gap between lab experiments and field applications. This article focuses on specific methods developed to evaluate the whole sensing chain, with an emphasis on (i) commercially-available optoelectronic instruments and (ii) sensing cable. A number of additional considerations for a successful pairing of these two must be taken into account for successful field applications. These considerations are further developed within this article and illustrated with practical applications of water leakage detection in dikes and concrete structures monitoring, making use of distributed temperature and strain sensing based on Rayleigh, Raman, and Brillouin scattering in optical fibers. They include an adequate choice of working wavelengths, dedicated localization processes, choices of connector type, and further include a useful selection of traditional reference sensors to be installed nearby the optical fiber sensors, as well as temperature compensation in case of strain sensing.

0 Reads | 9 Citations
2009
Dec
01
Published new article






Distributed Optical Fibre Sensors for Structural Health Monitoring: Upcoming Challenges

Published: 01 December 2009 by IntechOpen in Optical Fiber New Developments

doi: 10.5772/7569

0 Reads | 0 Citations
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