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Fiber Optic Sensors For Detection of Toxic and Biological Threats

Photonics Laboratories, Inc., Philadelphia, Pennsylvania, 19104, USA
Author to whom correspondence should be addressed.
Sensors 2007, 7(12), 3100-3118;
Received: 2 October 2007 / Accepted: 29 November 2007 / Published: 4 December 2007
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Protection of public and military personnel from chemical and biological warfareagents is an urgent and growing national security need. Along with this idea, we havedeveloped a novel class of fiber optic chemical sensors, for detection of toxic and biologicalmaterials. The design of these fiber optic sensors is based on a cladding modificationapproach. The original passive cladding of the fiber, in a small section, was removed and thefiber core was coated with a chemical sensitive material. Any change in the opticalproperties of the modified cladding material, due to the presence of a specific chemicalvapor, changes the transmission properties of the fiber and result in modal powerredistribution in multimode fibers. Both total intensity and modal power distribution (MPD)measurements were used to detect the output power change through the sensing fibers. TheMPD technique measures the power changes in the far field pattern, i.e. spatial intensitymodulation in two dimensions. Conducting polymers, such as polyaniline and polypyrrole,have been reported to undergo a reversible change in conductivity upon exposure tochemical vapors. It is found that the conductivity change is accompanied by optical propertychange in the material. Therefore, polyaniline and polypyrrole were selected as the modifiedcladding material for the detection of hydrochloride (HCl), ammonia (NH3), hydrazine(H4N2), and dimethyl-methl-phosphonate (DMMP) {a nerve agent, sarin stimulant},respectively. Several sensors were prepared and successfully tested. The results showeddramatic improvement in the sensor sensitivity, when the MPD method was applied. In thispaper, an overview on the developed class of fiber optic sensors is presented and supportedwith successful achieved results. View Full-Text
Keywords: Fiber Optic Sensors; Chemical Sensors; Biological Sensors; Home Land Security; Fiber Optics; Gas Sensors; Sarin Detection Fiber Optic Sensors; Chemical Sensors; Biological Sensors; Home Land Security; Fiber Optics; Gas Sensors; Sarin Detection
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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El-Sherif, M.; Bansal, L.; Yuan, J. Fiber Optic Sensors For Detection of Toxic and Biological Threats. Sensors 2007, 7, 3100-3118.

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