Fiber optic chlorine sensor based on evanescent field absorption

The feasibility of detecting chlorine in water by using a fiber-optic technique is investigated. The technique is based on evanescent field absorption through the color development of reacting diethyl phenylene diamine with chlorine, which forms an azo compound. Transmission attenuation results through color absorption of the fiber-optic waveguide from the azo species surrounding the fiber. Sensor systems with single- and multifiber sensing elements have been designed, constructed, and evaluated for linearity of response, sensitivity, and reproducibility of results. The experimental results establish the feasibility of detecting low-concentration chlorine in water using the proposed fiber-optic technique