Improved fiber optic sensor for salt concentration based on polymer swelling

Abstract
An improved design for fiber optic chemical sensors based on polymer swelling is applied to the detection of changes in electrolyte concentration. In this design the polymer sensing element is isolated from the fiber optics by a rubber diaphragm glued to a reflecting piece of aluminum. Changes in polymer size move the diaphragm, changing the intensity of light reflected into an optical fiber. The sensor design allows the user to adjust the distance between the optical fibers and the reflecting surface so that maximum sensitivity can be achieved. The new design is demonstrated using a bead of crosslinked strongly basic anion exchange resin as a sensing element to detect changes in electrolyte concentration.