光纤振动传感器波长解调方法研究

Research on Wavelength Demodulation Technology of Fiber Optic Vibration Sensor

研究了一种基于长周期光纤光栅的振动传感器波长解调方法,可解调波长范围为1 522～1 538 nm。宽带光源的出射光经光纤布喇格光栅反射后,入射到长周期光栅,经长周期光栅调制后光纤布喇格光栅反射光强会发生变化。通过对谐振波长处光功率的探测,实现光纤布喇格光栅静态、动态信号的监测。通过温度测量实验对监测系统进行标定,实验中光纤布喇格光栅传感器波长偏移量与系统输出电压成线性关系,比值为0.01 nm/mV。将传感器粘贴于铝板表面,采用该系统解调简支铝板结构的微小振动引起的波长变化。系统采集到的动态信号时域波形及频谱与涡电流位移计的测量结果相吻合,表明该系统可实现1 kHz以上的动态应变测量。

A fiber bragg grating（FBG） wavelength demodulation based on long-period fiber grating（LPFG） with wavelength range from 1 522 nm to 1 538 nm is studied.The outgoint light of broad optical source reflected by FBG is incident on LPFG,reflective light intensity of fiber bragg grating modulated by LPFG is changed.By detecting the transmission power at the resonance wavelength of the FBG,the static and vibration signal monitoring of FBG is realized.The monitoring system is calibrated by temperature-measuring experiment,it is found that the wavelength change of FBG sensor is linear to output voltage of the monitoring system and the ratio is 0.010 nm/mV.A FBG sensor is stuck on the surface of aluminum speciment and the wavelength change of FBG caused by vibration of the speciment is monitored by the demodulation system.The acquired vibration signal and fast Fourier transform of the experimnet data is analysised and it agrees with the signal of eddy current displacement meter.It is hopeful that the FBG wavelength demodulation is used to monitor more than 1 kHz dynamic signal.