非均匀应变场中光纤布拉格光栅的数值分析

当非均匀应变场作用在光纤布拉格光栅（FBG）上时，由于FBG周期和有效折射率在沿FBG长度方向都为变量，所以会导致光谱形状的变化。采用耦合模理论和龙格库塔的方法可以准确地分析非均匀应变场中的FBG光谱特性，其缺点是收敛速度慢；而传输矩阵法虽然可以大大提高收敛速度，但是由于忽略了非均匀应变场的变化梯度，在分析变化率较大的非均匀应变场时与龙格-库塔方法相比准确度较差，通过改进适用于分析非均匀应变场的FBG等效周期，既保留了传输矩阵分析FBG的快速收敛性，又保证了分析准确性。

Numierical Analysis of Fiber Bragg Grating Under Inhomogeneous Strain Fields

The spectrum of fiber Bragg grating(FBG) in inhomogeneous strain fields is distorted due to its inhomogeneity of both the periods and the effective refractive index.The coupling mode theory and Runge-Kuta method can be employed to exactly simulate the spectrum of FBG in such fields,but the convergence speed is slow.On the other hand,although the transfer matrix method could be used instead for higher convergence speed,the precision is poor because of the neglect of the grads of strain change.By improving the FBG equivalent period,a novel simulation method based on modified transfer matrix method is proposed,which has the advantage of quick-convergence as well as good accuracy.