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剥层法是重构光纤Bragg光栅(FBG)参数的常用方法 ,利用剥层法可以解调FBG非均匀应变。常规剥层法获得的FBG复耦合系数存在误差,为提高非均匀应变解调精度,提出基于剥层法的复耦合系数幅值修正改进方法。新方法在剥层求解当前层复耦合系数后,保留耦合系数相位,对耦合系数幅值进行修正,构成新的复耦合系数用于下一层反射谱的剥层求解。给出了改进算法求解非均匀应变的详细步骤和过程,并进行了仿真实验研究。利用传输矩阵法模拟仿真无应变、应变线性增大、应变线性减小以及二次曲线应变下的FBG反射谱,分别使用常规方法和改进的方法对各反射谱进行应变解调。结果表明:改进的方法获得的应变结果与理论应变有更高的一致性;不同理论应变下,改进的方法获得应变最大误差均值约为原始方法的1/5,均方根误差的均值约为原始方法的1/7,改进的方法解调误差远小于原始方法。
Peeling method is a common method to reconstruct fiber Bragg grating (FBG) parameters. Non-uniform strain of FBG can be demodulated by peel-off method. In order to improve the demodulation accuracy of non-uniform strain, an improved method of amplifying the complex coupling coefficient based on the peel-off method is proposed. The new method preserves the phase of the coupling coefficient after the layer is stripped to solve the complex coupling coefficient of the current layer, and modifies the amplitude of the coupling coefficient to form a new complex coupling coefficient for the stripping solution of the next reflection spectrum. The detailed steps and processes of the improved algorithm to solve the non-uniform strain are given, and the simulation experiments are carried out. The transmission matrix method is used to simulate strain-free, strain-linear increase, linear strain reduction and FBG reflection spectra under quadratic curve strain, and the strain spectra of each reflection spectrum are demodulated by the conventional method and the improved method respectively. The results show that the strain obtained by the improved method has a higher consistency with the theoretical strain. Under different theoretical strains, the average value of the maximum error obtained by the improved method is about 1/5 of the original method, and the mean value of the root mean square error The original method of 1/7, the improved method of demodulation error is much smaller than the original method.