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研究了应用法布里－珀罗（简称Ｆ－Ｐ）干涉仪实现气体或透明液体折射率和浓度相干检测的原理，给出了检测系统的主要设计方法和技术参数．该系统主要由光纤Ｆ－Ｐ传感器、ＣＣＤ光电转换器、接口电路和微机组成，主要特点是实现了对折射率和浓度的实时、连续、动态跟踪和高精度测量．我们导出了待测介质的折射率或浓度的变化量随干涉条纹的变化量变化的函数关系式，提出了干涉条纹的“中心位置定位法”，设计了干涉条纹动态跟踪的完整算法，并进一步导出了折射率或浓度的变化量随干涉条纹扫过的ＣＣＤ象元的数量变化的函数关系式．最后，具体计算了干涉条纹的检测精度和折射率或浓度的测量精度，分析了影响测量精度的因素，给出了提高测量精度的方法．
The principle of coherent detection of refractive index and concentration of gas or transparent liquid by Fabry-Perot (F-P) interferometer is studied. The main design methods and technical parameters of the detection system are given. The system mainly consists of optical fiber F-P sensor, CCD photoelectric converter, interface circuit and microcomputer. Its main feature is real-time, continuous, dynamic tracking and high-precision measurement of refractive index and concentration. We derive the function of the change of the refractive index or concentration of the measured medium with the variation of the interference fringes, put forward the “center location method” of interference fringes, and design a complete algorithm of dynamic tracking of interference fringes. A function of the change in the number of CCD pixels swept over by the interference fringes as a function of the amount of change in refractive index or concentration is derived. Finally, the detection accuracy of interference fringes and the measurement accuracy of refractive index or concentration are calculated. The factors that affect the measurement accuracy are analyzed, and the methods to improve the measurement accuracy are given.