Fiber Optic Chemical Sensors (FOCs) Information

FOCs are coating-based sensors on fiber optics that detect contaminants by monitoring the change in the refractive index on the coating of the fiber optics that alters the amount of light transmitted to a detector. They may operate by transporting light which, either by wavelength or intensity, provides information about analytes in the environment surrounding the sensor. FOCs can be characterized as intrinsic or extrinsic; extrinsic – use an optical fiber to transport light, e.g. laser induced fluorescence cone penetrometer. Intrinsic FOCs use the fiber directly as the detector; the sensor is then placed directly into the media to be analyzed; interaction of the analyte with the chemically selective layer creates a change in absorbance, reflectance, fluorescence or light polarization. The optical change is then detected by measuring the change in light characteristic carried by the optical fiber.
Fiber optic chemical sensors have been used to detect gas vapors, humidity, ions and organic compounds. One example of their use in environmental cleanup: FOCs have been used to measure volatile petroleum constituents, such as BTEX and chlorinated VOCs such as TCE, PCE, and carbon tetrachloride in groundwater, water, air or soil gas.

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