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Optical Engineering

Optical refractometer based on multimode interference in a pure silica tube
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Paper Abstract

A multimode interferometer based-fiber optic sensor with a silica tube section aimed to measure refractive index (RI) variations of surrounding liquids is presented. The sensing head is a silica tube section fusion spliced to single mode fibers operating in transmission. In the splice regions tapers were made to allow the light to be guided in the silica tube while the core is formed by air. This configuration permits measurements of refractive index variations with sensitivities of 101.1, 106.29, and 107.97 nm/RIU considering resonances with different wavelengths. The same resonances were tested with temperature variations with sensitivities achieved of 7.8, 8.7, and 9.3 pm/ °C, respectively. The spectral variation associated with one degree temperature change corresponds to a refractive index change of ~8 × 10-5, proving the low temperature dependence compared with sensitivity to RI variations.

Paper Details

Date Published: 1 October 2011
PDF: 4 pages
Opt. Eng. 50(10) 100504 doi: 10.1117/1.3646393
Published in: Optical Engineering Volume 50, Issue 10
Show Author Affiliations
Luís Coelho, INESC Porto (Portugal)
Orlando Frazão, INESC Porto (Portugal)
Jens Kobelke, Institut für Photonische Technologien e.V. (Germany)
Kay Schuster, Institut für Photonische Technologien e.V. (Germany)
José Luís Santos, Univ. do Porto (Portugal)

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