Unclad Evanescent Wave Fiber Optic Sensor for Toxic Gas Detection

In this book we present the design and construction of an evanescent wave fiber optic sensor for sensing the toxic gas (ammonia). The design of this fiber optic sensor is based on a cladding modification approach. A step index plastic multimode fiber with unclad middle region acts as the sensing element. The experimental results show a positive response to ammonia vapor at various concentrations. The sensing probe length source intensity and source wavelength shows an influence on the sensor response. The theoretical designing of sensing probe has also been presented here. Finally fiber optic is used to detect organic gases (Acetone) at different exposure time.