El-Sherif Mahmoud, Bansal Lalitkumar, Yuan Jianming
Photonics Laboratories, Inc., Philadelphia, Pennsylvania, 19104, USA.
Sensors (Basel). 2007 Dec 4;7(12):3100-3118. doi: 10.3390/s7123100.
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.
保护公众和军事人员免受化学和生物战剂的伤害是一项紧迫且日益增长的国家安全需求。基于这一理念，我们开发了一类新型光纤化学传感器，用于检测有毒和生物物质。这些光纤传感器的设计基于包层改性方法。在光纤的一小段中，去除其原有的无源包层，然后在光纤芯上涂覆一种化学敏感材料。由于特定化学蒸汽的存在，改性包层材料的光学性质发生任何变化，都会改变光纤的传输特性，并导致多模光纤中的模式功率重新分布。总强度测量和模式功率分布（MPD）测量都被用于检测通过传感光纤的输出功率变化。MPD技术测量远场图案中的功率变化，即二维空间强度调制。据报道，诸如聚苯胺和聚吡咯之类的导电聚合物在暴露于化学蒸汽时会发生电导率的可逆变化。研究发现，电导率变化伴随着材料光学性质的变化。因此，分别选择聚苯胺和聚吡咯作为改性包层材料来检测盐酸（HCl）、氨（NH₃）、肼（H₄N₂）和二甲基甲基膦酸酯（DMMP，一种神经毒剂沙林的模拟剂）。制备了多个传感器并成功进行了测试。结果表明，当应用MPD方法时，传感器的灵敏度有了显著提高。本文对所开发的这类光纤传感器进行了概述，并给出了成功取得的结果作为支撑。
