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

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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.