倾斜长周期光栅级联谱特性及折射率传感研究
Cascade Spectrum Characteristics and Refractive Index Sensor of Long Period Tilted Grating

基于耦合模式理论和折射率传感理论，通过传输矩阵法分析了级联倾斜长周期光纤光栅(Cascade Tilted Long Period Fiber Bragg, CTLPFG)的光谱特性和折射率传感特性。本文分别模拟了不同级联长度、级联角度、级联位置下的CTLPFG的谱特性，最后又模拟了不同环境折射率对CTLPFG不同包层模式的有效折射率的影响。研究结果表明：级联长度达到一个周期长度或者级联位置靠近光栅两端时，传输谱中的两个主损耗峰会逐渐变成一个主损耗峰；当只改变一个TLPFG倾角时，会对损耗峰的带宽产生影响；包层模式的有效折射率会随着外界环境折射率的增大而增大，并且高阶包层模式的有效折射率对环境折射率的变化更加敏感。因此，可以通过利用CTLPFG的不同参量之间的互补特性来设计出所需要的传输谱。
Based on coupling mode theory and refractive index sensing theory, The spectral characteristics and refractive index sensing characteristics of cascaded inclined long-period fiber grating (Cascade Tilted Long Period Fiber Bragg, CTLPFG) were analyzed by transmission matrix method. In this paper, the spectral characteristics of CTLPFG with different cascade lengths, cascade angles and cascade positions are simulated respectively. Finally, the effects of different ambient refractive index on the effective refractive index of CTLPFG with different clad-ding modes are simulated. he results show that when the cascade length reaches a period length or the cascade position is close to the two ends of the grating, the two main loss peaks in the transmis-sion spectrum gradually become one main loss peak. When only one TLPFG Angle is changed, the bandwidth of the loss peak will be affected. The effective refractive index of cladding mode increas-es with the increase of ambient refractive index, and the effective refractive index of higher order cladding mode is more sensitive to the change of ambient refractive index. Therefore, the required transmission spectrum can be designed by using the complementary characteristics between dif-ferent parameters of CTLPFG.