| Surface plasmon resonance (SPR) is a physical phenomenon, which will happen when incident light with a certain angle or wavelength incidents into the interface of metal film and other medium, meanwhile the wavevector component of incident light in the interface equals to the wavevector of surface plasmon wave. At this time, the total reflection attenuation appears because the total reflection condition in the interface is broken. SPR-based sensors can detect variations of the refractive indice of the medium on the sensor surface with high accuracy and sensitivity. SPR-based prism sensors appeared in the 1960's and have been widely used in biochemistry, medicine, environmental protection and other fields. SPR-based fiber optic sensors appeared in the 1990's and have greater prospects for study due to its small size, fast response, low cost and online real-time detection.The study for SPR-based fiber optic chemical sensor mainly includes the following two aspects:the choice of sensitive materials and the design of SPR sensing system, and the preparation and investigation of sensitive materials faced to target molecules are the basic of the whole research work.In this thesis:(a) the principle of SPR-based fiber optic chemical sensor and the effects of various parameters on the transmission spectrum and resonant wavelength of SPR-based fiber optic sensor were studied, and SPR-based fiber optic chemical sensing system was constructed; (b) the sensitive materials for target molecules were prepared and studied, including the selection and preparation, the recognition mechanism for target molecules, the dielectric properties and gas sensing properties. The details are as follows:(1) Using the weakly guiding dispersion equation, the core and cladding effective refractive indices of three layers' model were calculated; then the self-coupling coefficient and core-cladding coupling coefficient were calculated; at last, the sensitivity of long period fiber grating (LPFG) was analyzed.(2) Using the dispersion equation under infinite cladding radius, weakly guiding dispersion equation and doubly cladding dispersion equation, the effective refractive indices of fiber core under three different conditions were calculated, then the sensitivity of ThFBG was analyzed via changing the external medium refractive index and core radius.(3) Using numerical calculations for the S PR-based fiber optic sensors with four-layer models, the effects of the thicknesses and dielectric constants of metal layer and sensing layer on the transmitted spectrum, resonance wavelength and sensitivity were studied, meanwhile the appropriate input parameters and the sensitivity were obtained. Compared with LPFG and ThFBG sensing system, the SPR-based fiber optic sensing system has higher sensitivity.(4) Cobalt and copper phthalocyanine were synthesized with phthalic anhydride and urea, and alkoxy substituted copper phthalocyanine was synthesized via DBU catalytic method. Their peformance were characterized and analyzed by using SEM, XRD, IR and UV-Vis.(5) By controlling the solution concentration of metalphthalocyanine (MPc) and spin speed of spin-coating apparatus, the MPc films with different thicknesses were prepared. Furethermore, their optical properties of refractive index and gas sensing behaviour were detected by using UV-Vis and ellipsometer technique.(6) The refractive indices of cryptophane-A and silicone SE-30 were calculated by using group contribution method. Then the refractive index of the composite sensitive film was calculated by using two-component calculation method. Moreover, the process of CH4 molecules encapsulated into cryptophane-A was analyzed. At last, the relationship between the refractive index of composite sensitive film and the concentration of CH4 was obtained.
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