Fiber optic volatile organic compounds sensor based on polymer coated FBG refractometer

Fiber Bragg Grating (FBG) refractometer for liquid refractive index monitoring and its applications have been widely studied in the past few decades. This paper proposes a novel fiber optic volatile organic compounds (VOCs) sensor, achieved by means of polymer film coated high performance FBG refractometer, i.e. cladding removed FBG or even core thinned FBG. Polymer film coated sensor has partial selectivity, which makes this kind of sensors suitable for optical nose systems. While being exposed to VOCs, the sensing layer swells and its refractive index changes at the same time. Transduction part of this sensor, the thinned FBG, works as both strain transducer and refractometer. The mathematical model of the FBG VOCs sensor is introduced and experimentally evaluated with OV-1 coated FBG refractometer, which shows partial selectivity to different vapors and about 100 ppm detection limit to toluene.