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Optical detection of volatile organic compounds using selective tensile effects of a polymer-coated fiber Bragg grating.

We demonstrated a novel selective chemical sensing approach by incorporating a poly(dimethylsiloxane) (PDMS)-coated fiber Bragg grating (FBG) structure for optically detecting various volatile organic compounds (VOC's). When the proposed structure is exposed to a nonpolar solvent, a tensile stress is induced between the coated PDMS and the optical fiber by a VOC-dependent swelling effect of the PDMS, which results in a Bragg wavelength shift dependent on the concentration and the type of VOC's. Because of no need of an etching process of a fiber cladding, the proposed PDMS-coated FBG can be used as a simple, convenient, and durable chemical sensing element with a high sensitivity, compared with conventional FBG sensors requiring an evanescent wave coupling.