中文摘要：

基于长周期光纤光栅（ LPFG）包层有效折射率与包层半径、折射率和环境折射率的良好相关性,提出一种LPFG的新颖结构。利用传输矩阵法和三包层光纤的色散方程对其建模,mathcad15计算软件进行数值仿真和模拟。得到新型结构LPFG谐振峰发生分裂,即一个透射峰分裂为两个；两个分裂峰谐振波长间距随着腐蚀段包层半径的减小或填充材料厚度的增大而增加,模式越高增加越快；同时分裂峰间距在填充材料折射率小于1.4和大于1.48时基本不变,而在1.4和1.48之间分裂峰间距变化显著,在1.44附近达到极值。此种结构LPFG设计上的特殊性即可弥补半腐蚀LPFG容易断的不足,又可通过填充敏感材料且利用分裂峰间距定标而提高气体或液体浓度传感灵敏度。

英文摘要：

A novel LPFG structure was proposed based on the excellent relation between effective refractive index of cladding,radius and refractive index of cladding and environment refractive index. A theoretical model was built using transmission matrix method and dispersion equation of three-layered fiber,and then numerical simulation was carried out by Mathcad15 software. The simulation results show that the resonance peak is divided into two peaks, and the gap between them is increased when decreasing the cladding radius of the etched section or increasing the thickness of the filling materials. The gap increase is more rapid for the higher order mode. Moreover, the gap between the divided peaks remains unchanged when the refractive index of the filling materials n is less than 1 . 4 and more than 1 . 48 . The gap change is remarkable when the refractive index is in the 1 . 4＆lt;n＆lt;1 . 48 range and it reaches the maximum at n=1 . 44 . The specific LPFG structure designed in this manuscript can not only compensate for the defect of easy-to-breaking for half-etched LPFG,but also increase the detection sensibility to gas and liquid by changing the filling materials and calibrating the gap between the divided peaks.