Fiber optic chemical sensors using a modified conducting polymer cladding

Abstract

A new class of sensors has been designed and prepared based on replacing the original cladding material on a small section of an optical fiber with a conducting polymer or other environmentally sensitive material. Vapor induced chemical interactions with the polymer result in refractive index and optical absorption changes in the polymer cladding. These changes lead to an optical intensity modulation induced within the multi-mode optical fiber. Polyaniline and polypyrrole were used as the modified cladding material on the fiber core. An in-situ deposition method was used to produce uniform thin film coatings of the electronic polymer on the optical fiber. It was found that optimization of the sensor sensitivity can be achieved by selecting the proper incident wavelength, excitation conditions, and optical detection technique. Chemical sensors were developed and tested for detection of HCl and NH3 vapors along with the reducing agent hydrazine. The results clearly demonstrate that conjugated polymer coated fiber optics represent a promising new approach for the detection of volatile toxic gasses.