Self-calibrated fiber optic transflection probe for NO_2 detection

摘要

The paper describes an optical fiber based sensor (FOS) for the detection of the pollutant gas, NO_2, in a mixture of gases. The design comprises of a fiber optic transflection probe with a sensor element placed at one end. In the present FOS, the transducing component is prepared by sol-gel process. An equal quantity of a diazotizing reagent together with a coupling reagent is immobilized in the sol-gel matrix, which forms an azo dye in the presence of NO_2. The sensor relies on the coloration reaction occurring at the micropores of this sol-gel film in the NO_2 environment and offers a consequent variation in the optical absorption at a specific wavelength. The current sensor design gives more than 85% of variation in the output intensity at a NO_2 concentration of few parts per million in air sample.