介绍了压电式光纤相位调制器的相移系数理论公式，提出了基于杨氏双缝干涉原理的相移系数测量方法。对测量方法的可行性进行分析，通过实验对测量方法进行了验证。实际研制了一个基于压电陶瓷环的光纤相位调制器件，实验测得的相移系数与理论分析结果基本一致。利用研制的压电式光纤相位调制器实现了两路准直光束之间的相位锁定，在远场实现了相干合成，干涉条纹可见度从3%提升至43%。

The theoretical formula of phase-shift coefficient of piezoelectric fiber optic phase modulator is introduced, and a measuring method of the phase-shift coefficient is suggested based on Young’s two-slit interference principle. The feasibility of this measuring method is analyzed, and then verified by experiments. A phase modulator device based on piezoelectric ceramic ring is developed, and the phase-shift coefficient is tested which is consistent with the theoretical result. A experiment of phase locking of two beams is carried out with the self-developed piezoelectric fiber optic phase modulator, and coherent beam combination in far-field is achieved successfully. The fringe visibility in phase-locking state is up to 43%, compared with 3% with phase-locking off.