采用小波变换提取弱反射光纤布拉格光栅干涉信号

Extraction of Interference Signal of Weak Reflection Fiber Bragg Grating by Wavelet Transform

提出一种提取基于迈克耳孙干涉的弱反射光纤布拉格光栅(WFBG)时分复用系统中干涉信号的方法,以降低数据采集量并提高零差对称解调精度。对光强信号进行连续小波变换,寻找变换系数的极值,相邻的极小值和极大值用于界定激光干涉区间。针对不同宽度的激光脉冲工况,调整小波尺度因子,以寻找干涉区间,分别基于干涉区间内光强信号的最大值和平均值得到干涉信号,最后采用零差对称算法解调干涉信号的相位信号。将WFBG传感器放入振动液柱内,多次测量同一弱正弦信号,并对测量信号进行正弦曲线拟合。拟合结果显示采用连续小波变换提取短脉冲干涉区间并以平均值法计算干涉信号有助于提高该传感系统的零差对称解调精度。

To reduce the data acquisition quantity and improve the accuracy of zero difference symmetric demodulation,a method for extracting interference signals in a time-division multiplexing system with a weak fiber Bragg grating(WFBG)based on Michelson interference is proposed.Continuous wavelet transform is applied to the intensity signal to find the extreme value of the transform coefficient.The adjacent minimum and maximum values are used to define the laser interference region.According to the laser pulses with different width,the wavelet scale factor is adjusted to find the interference region.The interference signal is obtained based on the maximum intensity and the average intensity in the interference region,respectively,and the phase signal of the interference signal is demodulated by the zero difference symmetry algorithm.The WFBG sensor is put into a vibrating liquid column.The same weak sinusoidal signal is measured repeatedly,and the measured signals are fitted by the sinusoidal curve.The fitting results show that extracting the short pulse interference region by the continuous wavelet transform and calculating the interference signal by the average value method are helpful to improve the zero difference symmetric demodulation accuracy of the sensing system.