Tapered MMF sensor fabrication using SnO2-NPs for alcohol sensing application

Metal oxide coated fiber optic sensor is proposed and experimentally characterized for alcohol sensing. The sensor probe design is based on the cladding removed methodology, done via tapering of the fiber. Chemical etching process was used to taper a section of multimode fiber (MMF) and the region was coated by tin dioxide nanoparticles (SnO2-NPs), which were synthesized by the sol–gel method. The sensing principle relies on the refractive index (RI) modification of SnO2 after being in contact with isopropanol solution leading to modulated output response. XRD structurally characterized SnO2-NPs and their crystallite size was found to be 19.88 nm. The prepared fiber dimension, nanoparticles morphology and the elemental composition were confirmed by FESEM and EDX characterization. A maximum average sensitivity with good linear behavior was found to be 22 counts/ppm for the wide range of concentrations (0–500 ppm). Along with excellent sensitivity, sensor shows nice reversibility and repeatability characteristics. A sensor combining optical fiber and metal oxide as sensing elements provides advantages of a miniaturized probe, low cost, ruggedness, online monitoring and remote sensing.