为测量压电换能器在快速交变电场驱动下的实际伸长变化，提出一种基于调频激光自外差信号解调技术的测量方法。该方法通过外差技术实现信号频谱搬移,避免了光电探测器接收时低频噪声的干扰，准确地获得了压电换能器端面速度的傅里叶谱；对傅里叶谱进行分析，从而获得压电换能器端面的速度曲线；对速度曲线积分，得到了伸长曲线。实验结果表明，基于调频激光调制解调技术测量压电换能器伸长曲线具有方法简单、信号质量好、精度和灵敏度高且误差小等优点。

In order to measure the actual elongation of piezoelectric transducer(PZT) driven by fast alternative electric field, a method based on frequency-modulation(FM) laser heterodyne signal demodulation technique is proposed. The method shifts the frequency spectrum of signal by using FM laser heterodyne technique so that the signal will not be disturbed by low-frequency noises. In that case, the Fourier spectrum of end plane velocity of PZT is measured accurately, with which the velocity variation can be deduced. Then, the elongation of PZT can be obtained by performing integration on the velocity. The results show that, this method simple, can acquire high quality signal easily, and has high sensitivity high accuracy.