中文摘要：

本文基于耦合模理论，建立了严格的四层金属膜理论模型，探讨了镀金属膜长周期光纤光栅(Long-penodfibergmtmg,LPFG)的温度、应变及折射率特性，以及镀膜参数对镀金属膜长周期光纤光栅光谱特性的影响。仿真结果表明，长周期光纤光栅表面最优的金属膜厚度将引起表现等离子共振（Surfaceplasmonresonance,SPR)特性，这一特性将使得LPFG对稳定及折射率都有较高的敏感性，而对应变影响较小。理论分析表明，银膜厚度在〇.8—1.2nm范围内时，折射率敏感度达到最大值为42.4026,敏感度增加4.5%。仿真结果为镀膜长周期光纤光栅的设计及参数优化提供了理论指导。

英文摘要：

To obtain the influence rules of the coating parameters of a long-period fiber grating(LPFG)with respect to temperature,strain and refractive index sensing properties,based on the mode coupling theory,a strict four-layer theorietical model of a metal film coated LPFG is established,and these parameters that affect the spectral characteristics of the metal film coated LPFG are studied.The simulation results show that there is an optimal metal film thickness on the surface of the LPFG that will induce the surface-plasmon resonance(SP R)effect,which results in higher sensitivity to the environmental temperature and refractive index but has little influence on the strain There is theoretical evidence that when the silver thickness is between0.8and1.2nm,the refractive index sensitivity will reach the peak point of42.4026,at which the refractive index sensor sensitivity is increased by4.S%.The theoretical results of coating a long-period fiber grating provide a good theoretical basis and guidance for LPFG design and parameters optimization