A distributed fiber optic chemical sensor for hydrogen cyanide detection

Abstract

A fiber optic hydrogen cyanide (HCN) sensor having its entire length as the sensing element is reported here. The optical fiber is multimode and consists of a pure fused-silica core and an HCN sensitive cladding. Upon exposure to HCN gas, the cladding rapidly changes color, resulting in attenuation of the fiber's light throughput. The fiber is used to detect HCN at part per million levels, which suggests that the propagating modes of light interact with the cladding. The sensitivity of the fiber as a function of sensor length and challenge concentration will be reported. Prior to exposure, the fiber attenuation measures less than 1 dB/m, making it possible to detect hydrogen cyanide on a continuous length of fiber on the scale of tens of meters. This technology could replace the need for having a collection of point-detectors to cover large areas, and hence lends itself to building and perimeter chemical detection.