Abstract

Several approaches have been previously investigated which utilize fiber optic sensors to determine the relative humidity of air. Such devices typically have the advantage of higher sensitivity and quantitative precision compared to traditional chemical indicators. For example, the use of an optical fiber evanescent sensor for humidity measurements has been described by Russell and Fletcher¹. In their device, a moisture sensitive cobalt chloride/gelatin film is immobilized on a 12cm long silica optical fiber as the humidity probe. Ballantine and Wohltjen described an optical waveguide humidity sensor that employed the same calorimetric reagent/polymer system on a glass capillary². Zhu and Hieftje utilized a fluorescent fiber optic sensor for atmospheric humidity³ based on a dye entrapped within a polymer matrix. However, all of these sensors can only determine the relative humidity above 40% because of sensitivity limitations.

© 1988 Optical Society of America