Optical Fiber Multi-Sensing System Using Liquid Crystal and Dye Films

1.在角锥棱镜上镀制了多种有机染料薄膜，对少量反应气体的颜色反应光谱、荧光光谱变化及其强度进行了测量、评价和选择。利用含有向列型液晶的胆甾型液晶，通过调节溶解比，制备了具有1.3μm选择反射带的胆甾型液晶盒。构造了表面涂有不同染料膜的角立方棱镜传感头，并用多变量参数法分析了酸性和/或碱性气体的光谱变化。从而实现气体物种的分离和检测。在实验结果的基础上，将一对胆甾型液晶盒和一个向列型液晶盒夹在涂有染料膜的棱镜和与光纤相连的杆状透镜之间，制成了多传感头。构建了多传感器系统，并对其性能进行了测试和评估。以不同锚定强度的取向膜为衬底，制备了液晶盒，并测量了分子取向状态的变化对液晶传输特性的影响。研究了分子在电场中的取向与锚定强度的关系，并对其性能进行了评价。上述多传感头通过光纤连接，传感系统采用OTDR方式实现，可以远程监测多种电器的异常现象。对研究结果进行了检验，并对研究工作进行了总结。

1. Various organic dye films are deposited on the corner-cube prism, and the color reaction spectra, fluorescent spectrum changes and their intensities for small quantity of reaction gases are measure, evaluated and selected for the research studies.2. Cholesteric liquid crystal cells with selective reflection band at 1.3 μm are prepared using cholesteric liquid crystals containing nematic liquid crystals with adjusted dissolving ratios.3. The sensor heads with the corner-cube prism of which surfaces are coated by different dye films are constructed, and spectrum changed for acid and/or base gases are analyzed by using multi-variable parameter method. Then the separation and detection of gas species can be attained.4. On the basis of experimental results, the multi-sensor heads are prepared by sandwiching a couple of cholesteric liquid crystal cells and a nematic liquid crystal cell between the corner-cube prism coated with dye films and the rod lens connected with the optical fiber. Then the multi-sensing system is constructed and its properties are measured and evaluated.5. The liquid crystal cells are prepared using the substrates coated with several alignment films, which have different anchoring intensities, and the dependence of transmission properties on the electric fields are measured as the change of molecular orientation states. Relations between the anchoring strength and the molecular orientation for the electric field are studied and the evaluations for their properties have been made.6. The multi-sensor heads above described are connected with the optical fiber, and the sensing system is implemented using an OTDR method, where abnormal phenomena of plural electric apparatuses can be monitored remotely.7. The results are examined and the research work is summarized.