非本征法珀型超声传感器输出信号的特征

Characteristics of output signal of extrinsic fiber Fabry-Perot acoustic sensors

根据多光束干涉原理制备了非本征光纤法珀(FP)型传感器,用于测量在液体中传播的超声波,分析了传感器灵敏度和幅频特性的影响因素,研究了其输出信号的特征。用镀膜的石英膜、尾纤端面和空气腔形成FP干涉腔。建立了传感器参数确定的方法,对石英膜的幅频特性进行了理论分析和实验验证。最后,建立了非本征光纤FP超声测量系统,讨论和验证了不同工作点状态对系统输出信号特征的影响。实验结果表明,本文制备的非本征法珀型超声传感器可以进行液体中超声的测量;传感器的一阶谐振频率为140 kHz,灵敏度为0.005 nm/Pa。该传感器的输出信号特征决定于工作点状态及输入信号的调制深度,当工作点位于工作曲线的线性区中点时,输出信号的灵敏度最高;当过调制时,输出信号出现倍频,可以扩大测量范围。

Based on multi-beam interference principle,an extrinsic fiber Fabry-Perot （FP） sensor was developed to measure the acoustic signal in liquid, whose interference cavity was consisted of quartz diaphragm,end of pigtail and air film. The sensitivity,amplitude-frequency and the output signals of the sensor were analyzed. The parameters of FP sensor were obtained to analyze amplitude-frequency characteristics of quartz diaphragm theoretically and experimentally. Finally, a measurement system on acoustic signals in water was developed and the effect of operation points on output signals were discussed and tested in different conditions. The experimental results indicate that the extrinsic fiber FP acoustic sensors in proposed system are able to measure acoustic signal in the liquid. Its fundamental frequency can reach to 140 kHz and sensitivity is 0. 005 nm/Pa. The characteristics of output signal of the sensors are dependent on operational points and modulation depths of input signal. The sensitivity of the sensor is optimial when the operational points lie in quadrature point of operation curve, the measurement region will be increased when the output signal is frequency double for over modulation.