通过对光纤法布里-珀罗(Fabry-Pérot cavity,F-P)腔单波长功率监测,对时域信号进行快速傅里叶变换(FFT),检测振动信号频率。建立了F-P腔的瞬时响应模型。发现透射响应比反射响应有微小延时,证明了F-P腔的多次反射原理对于一般频率不超过几十千赫兹的振动信号的测量没有影响。直接作用在F-P腔上的振动较强时,超过解调单值范围,波形发生畸变。通过增大振动源与F-P腔的距离控制解调单值性,当距离增至8 cm时,获得相对准确的解调结果。

Vibration signal frequency is measured by monitoring the single wavelength power of fiber Fabry-Pérot (F-P) cavity and applying fast Fourier transform (FFT) to the time domain signal. An instantaneous model is established and the minute response delay between transmission and reflection is shown. It is proved that the multi-reflection of F-P cavity has little influence on the measurement of vibration with a frequency generally not higher than some dozen kilohertz. The waveform will be distorted when the vibration directly applied on the F-P cavity is intense and out of the demodulation monotropic range. Desensiblization is implemented by increasing the distance between the vibration source and the F-P cavity to control the monodromy of demodulation and more accurate demodulation results are obtained when the distance is increased to 8 cm.