Midinfrared fiber sensor for the in situ detection of chlorinated hydrocarbons

摘要

An infrared fiber optic sensor has been developed for the in situ detection of chlorinated hydrocarbons and other pollutant species in water. The sensing element consists of a silver halide fiber, coated with an appropriate polymer. The polymer both enriches the chemical species to be measured in the evanescent wave region of the fiber and serves to exclude water from the measurement region. Evanescent wave spectrometry is then used to accurately quantify chemical species such as chlorinated hydrocarbons which have their strongest absorption bands above 10 $mu@m. In order to increase the evanescent absorbance signal, and therefore the sensitivity of the sensor, a number of novel launch designs and fiber configurations has been examined. Results from a range of such configurations are presented and conclusions are drawn regarding optimum sensor design.