27 August 2003 Environmental sensing of hydrocarbons in water using mid-infrared optical fibers
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The sensing of hydrocarbons, such as the BTEX compounds in water, is described. These hydrocarbons, which are constituents of petroleum can find their way into groundwater due to leaks in underground tanks and in associated piping, are known to be carcinogenic and threaten flora and fauna. An infrared fiber optic sensor based on the evanescent wave generated around the bare core fiber is utilised to perform qualitative and quantitative measurements on these analytes. A silver halide fiber is used for its low spectral attenuation between 4-16mm, for within this wavelength range the analytes have characteristic absorption peaks, which allow their concentrations in water to be determined using the Beer Lambert Law. Using narrow bandpass filters centred on a characteristic peak, the sensor can be selectively tuned to a single analyte. Coating the bare core with a hydrophobic plasticised PVC film increases analyte concentration within the active region of the sensor and minimizes water interference, which is considerable at these wavelengths.
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Raymond P. McCue, Raymond P. McCue, James Edward Walsh, James Edward Walsh, Fiona Walsh, Fiona Walsh, Fiona Regan, Fiona Regan, } "Environmental sensing of hydrocarbons in water using mid-infrared optical fibers", Proc. SPIE 4876, Opto-Ireland 2002: Optics and Photonics Technologies and Applications, (27 August 2003); doi: 10.1117/12.463965; https://doi.org/10.1117/12.463965

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