条纹计数法解调精度受限，而常用的高精度外差调频解调法(如相位生成载波法、线性调频法)，在光源调频过程中伴生有幅度调制并且调制解调系统复杂。提出了一种基于双光纤光路相位解调的法布里珀罗(F-P)位移传感器，原理上省去了光源调频过程，在提高检测精度的同时，成本与条纹计数法相当。与已有报道的双光路结构不同的是，该传感器对两干涉光路之间相位差无严格要求，安装调节简单，降低了传感器的工艺难度。位移测量实验结果表明，该传感器在0～500 μm的测量范围内，线性度为1.1%，误差限值为±3 μm。

To overcome the accuracy limits of fringe counting method for a Fabry-Perot (F-P) interferometer and the complexity of a higher resolution demodulation system such as phase generated carrier (PGC), linear frequency modulation (LFM) and heterodyne frequency modulation, where residual amplitude modulation always exists in frequency modulation, a dual-fiber F-P displacement sensor based on double-fiber phase demodulation is presented. The proposed demodulation scheme eliminates the modulation on light source, improves the accuracy, and keeps the system cost as low as that of the fringe counting method. Compared with the reported dual-fiber F-P structure, this design has no strict requirement for a specific phase difference between the two interference paths, which makes it more feasible for manufacturing. Experimental results demonstrate a good linearity of 1.1% and a resolution of ±3 μm within a measuring range of 0~500 μm for the sensor system.