采用双方波信号和B-样条小波解调弱反射光纤布拉格光栅

提出了一种采用双方波信号和B-样条小波解调弱反射光纤布拉格光栅(WFBG)的方法,并进行了实验验证.单个方波周期设置为相邻WFBG间光纤中激光往返传输的时间,对单个方波进行猝发操作形成双方波,则前WFBG反射的后方波与后WFBG反射的前方波重叠干涉.采用B-样条小波变换降低干涉信号的噪声,利用Hilbert变换对干涉信号进行π/2相移,对原干涉信号和相移后干涉信号比值进行反正切运算,得到干涉信号的相位信息.将间隔为50m的5-WFBG阵列置于木地板上,分别接收不同振幅和频率的正弦声波,采用上述方法解调的干涉相位信号能较好地反映声波信息.该解调方法解调光路简单,数据处理简单.

Demodulation of Weak Fiber Bragg Grating Using a Double Square Wave and B-spline Wavelet

A double square wave and B-spline wavelet for demodulation of a Weak Fiber Bragg Grating(WFBG)was proposed and demonstrated.A period of single square wave is set as the round trip time of laser transmission in the fiber between two adjacent WFBGs.The burst operation is conducted to the single square wave to form a double square wave,for which the rear square wave reflected by former WFBG and the front square wave reflected by latter WFBG overlap and interfere.B-spline wavelet transform is used to reduce the noise of interference signal.Hilbert transform is applied to produceπ/2 phase-shift of the interference signal.Arc tangent operation is conducted to the ratio of the interference signal with the phase-shifted signal to obtain the phase signal of the interference signal.A 5-WFBG array with 50 meters equispaced length is put on a wooden platform,and received sinusoidal sounds with different amplitudes and frequencies respectively.The experimental results can reflect the information of the sounds well.The advantage of the proposed demodulation method is that the optical structure and data processing is simple.