An Optical Fibre Sensor for Biofilm Measurement using Intensity Modulation and Image Analysis

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Abstract

he development of an online sensor to determine the fouling properties of aqueous process fluids is described. A plastic optical fiber with its cladding removed over a sensitized length measures the growth of biofilms in a closed loop water process system by evanescent field attenuation and intensity modulation. The sensor detects material build-up at the core-cladding interface by means of refractive index modulation. A theoretical model is developed showing that an increase in cladding refractive index reduces the intensity of light propagating in the fiber and attenuates the high order modes. The modulation mechanism of the sensor is demonstrated using a CCD camera and frame grabber to record the far field modal distribution of the fiber, when the outer modes are excited. The intensity distribution changes spatially in response to the biofilm deposit on the sensor, indicating evanescent field attenuation

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CCD image sensors biological techniques fibre optic sensors image processing intensity modulation microorganisms optical fibre cladding optical information processing optical modulation optical polymers refractive index measurement CCD camera aqueous process fluids biofilm deposit biofilm measurement biofilms cladding refractive index closed loop water process system core-cladding interface evanescent field attenuation far field modal distribution fouling properties frame grabber high order modes image analysis intensity distribution intensity modulation light propagation intensity material build-up modulation mechanism online sensor optical fiber sensor outer modes plastic optical fiber refractive index modulation sensitized length

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