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1 October 2011 Optical refractometer based on multimode interference in a pure silica tube
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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.
©(2011) Society of Photo-Optical Instrumentation Engineers (SPIE)
Luís Coelho, Orlando Frazão, Jens Kobelke, Kay Schuster, and José Luís Santos "Optical refractometer based on multimode interference in a pure silica tube," Optical Engineering 50(10), 100504 (1 October 2011).
Published: 1 October 2011

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