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Article Dans Une Revue IEEE Sensors Journal Année : 2021

Direct Non-Invasive Measuring Techniques ofNanometric Liquid Level Variations UsingExtrinsic Fiber Fabry–Perot Interferometers

Résumé

This article investigates two different non-contact non-invasive solutions for measuring nanometric-order liquid-surface displacements with Extrinsic FiberFabry-Perot interferometers. They are investigated fordeveloping hydrostatic leveling sensor (HLS) systemstargeting the detection of very slowly-evolving movementsin geophysics and geotechnics. In the first technique,the sensing beam from the interferometer traverses a liquidof known refractive index and is reflected by a mirrorsubmerged at the bottom of the HLS vessel. The liquid-levelvariation is thus sensed as a variation of the optical pathlength of the interrogating beam. The second solution, on theother hand, directly exploits the reflection of the sensingbeam at the air-liquid interface in the absence of a reflective surface in the vessel. The subsequent variation of liquid levelis then measured directly as the beam’s optical path variation in air. The common denominator of these two techniquesis an Extrinsic Fabry-Perot sensor with nanometric precision operating at a wavelength of∼1310 nm. The interrogatingbeam suffers from high IR absorption in water, hence the latter solution is more advantageous in terms of dynamicrange. In applications where liquids other than water canbe employed, the use of low optical absorption liquids suchas Polydimethylsiloxanic fluids is recommended at this operating wavelength. Being more viscous and less volatile thanwater, these fluids can significantly improve the noise floor of HLS systems, hence contributing to a larger dynamicrange, lower instrumental drift and higher signal-to-noise ratio.
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Dates et versions

hal-03089317 , version 1 (28-12-2020)

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Patrick Chawah, Renaud Briand, Valerie Dupe, Frederick Boudin, Michel Cattoen, et al.. Direct Non-Invasive Measuring Techniques ofNanometric Liquid Level Variations UsingExtrinsic Fiber Fabry–Perot Interferometers. IEEE Sensors Journal, 2021, 21 (2), pp.1580-1587. ⟨10.1109/JSEN.2020.3020512⟩. ⟨hal-03089317⟩
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