Optoelectronic sensor for chemical detection in liquid by using ultra thin polymer coating on long period fiber gratings

In this work, a novel fiber optic sensor able to measure the concentration of organic analytes, in aqueous environment is presented. The proposed structure relies on the use of long period gratings (LPGs), as high sensitivity refractive index transducers, coated with thin films of syndiotactic polystyrene (sPS) in the nanoporous crystalline δ form, as sensitive polymeric layer. The combination of the intrinsic and high refractive index sensitivity of the LPGs with the high sorption properties towards chlorinated and aromatic compounds of sPS δ form allows detecting very low concentrations (in the range of few ppm) of analytes in water. Chemical detection is carried out by measuring the wavelength shift and the amplitude changes in the attenuation bands of the LPG due to analyte sorption.