利用OptiGrating软件研究了TFBG(倾斜光纤光栅)在环境折射率变化极其微小的情况下不同模式的光谱特性。结果表明, 微小环境折射率的变化对纤芯模与幻影模的影响甚微, 却对包层模影响较大。由于变化极小, 包层模谐振波长的漂移可以忽略, 只需考虑谐振峰深度的变化。发现波长在1 542 nm附近的高阶包层模对环境折射率高度敏感, 并且在一定的范围内灵敏度极高, 最高可达10-5 量级, 在高精度折射率传感领域前景广阔。

In this paper, we use OptiGrating software to investigate the spectral characteristics of TFBG different modes when surrounding refractive index changes extremely little. Result shows that the micro change of refractive index has very little impact on core mode and phantom mode, but has great impact on the cladding modes. Because the change is very little, the drift of cladding mode resonant wavelength can be neglected, and only the variation of the resonant peak depth needs to be considered. The high-order cladding modes near 1 542 nm wavelength are sensitive to the surrounding refractive index. In a certain range of refractive index,the precision is extremely high with orders of magnitude up to 10-5 . The simulation results obtained in this paper has broad prospects in high precision refractive index sensing field.