25 October 2011 Liquids analysis using back reflection single-mode fiber sensors
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We demonstrate a new and simple configuration for measuring physical properties of liquids. With proper data analysis, the proposed setup can potentially extend its application to chemical analysis and characterization of two-phase fluids. The fiber sensor is based on the characteristic reflection spectrum obtained from different samples allocated on the tip of a cleaved single-mode optical fiber. Different tests fluids provide a distinctive reflection spectrum and the physical properties of the sample can thus be inferred through spectral analysis. Our experiments are based on a single mode optical fiber dipped into the liquid of interest and a fiber Bragg grating (FBG) interrogator for registering the backreflected light. We analyze how the pending drops formed on the tip of the fiber generate an interference pattern whose features depend on the physical properties of the test liquid. The experimental setup is controlled through a virtual instrument to perform the tests automatically. Each experiment involves data acquisition from the FBG interrogator and recording images by means of a CCD camera. Image analysis provides information about the geometry of the drop and fiber positioning is carefully controlled to provide consistent reflection patterns for different experiments with the same sample. Preliminary results show the correlation between the spectral response and the drop's geometry, which in turn is directly related to surface tension of the liquid sample. The performance of the proposed configuration is evaluated with two liquids (glycerin and PDMS polymer) showing the feasibility of this approach for developing a simple fiber optic liquid analyzer.
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Víctor Salazar-Haro, Víctor Salazar-Haro, Violeta Márquez-Cruz, Violeta Márquez-Cruz, Juan Hernández-Cordero, Juan Hernández-Cordero, } "Liquids analysis using back reflection single-mode fiber sensors", Proc. SPIE 8011, 22nd Congress of the International Commission for Optics: Light for the Development of the World, 80114W (25 October 2011); doi: 10.1117/12.902186; https://doi.org/10.1117/12.902186

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