光纤开腔法布里–珀罗干涉仪的折射率传感特性研究

Refractive Index Sensing Characteristics of an Open-Cavity Fiber-Optic Fabry-Perot Interferometer

摘要: 本文提出并设计了一种基于光纤开腔法布里–珀罗干涉仪(Fabry-Perot Interferometer, FPI)的折射率传感器。该传感器采用全开腔结构与U型玻璃槽封装，通过单模光纤端面与镀金玻璃圆柱构成干涉腔，有效提升液体导入能力与结构稳定性。随着待测溶液折射率变化，FPI干涉光谱特征峰发生明显漂移，通过对特征波长解调，实现了溶液折射率的高精度测量。实验结果表明，在折射率范围1.3329~1.3343内，传感器折射率灵敏度达到1149.265 nm/RIU，线性拟合系数为0.998。对不同腔长结构的对比实验表明，该传感器具有良好的重复性与工艺一致性，灵敏度偏差小于0.5%。此外，稳定性测试结果显示，在恒定环境下120 min内波长漂移小于0.091 nm，对应折射率误差约为7.9 × 10⁻⁵ RIU。该传感器具有结构简单、成本低、抗腐蚀性强及良好稳定性等优点，在生化检测与工业过程监测等领域具有良好的应用前景。

Abstract: This paper proposed and designed a refractive index sensor based on a fiber-optic open-cavity Fabry-Perot interferometer (FPI). The sensor employs a fully open-cavity structure encapsulated in a U-shaped glass channel, in which the interference cavity is constructed by the end face of a single-mode fiber and a gold-plated glass cylinder. This design effectively improves liquid intake capacity and structural stability of the sensor. The characteristic peaks in the FPI interference spectrum exhibit a remarkable wavelength shift with the variation of the external refractive index, and high-precision measurement of the solution’s refractive index is achieved by demodulating the characteristic wavelengths. Experimental results indicate that within the refractive index range of 1.3329 to 1.3343, the sensor achieves a refractive index sensitivity of 1149.265 nm/RIU, with a linearity coefficient of 0.998. Comparative experiments on structures with different cavity lengths demonstrate that the sensor exhibits excellent repeatability and process consistency, with a sensitivity deviation of less than 0.5%. Furthermore, stability test results show that under constant environmental conditions, the wavelength drift over 120 minutes is less than 0.091 nm, corresponding to a refractive index error of approximately 7.9 × 10⁻⁵ RIU. This sensor offers advantages such as a simple structure, low cost, strong corrosion resistance, and high stability, and holds promising application prospects in fields such as biochemical detection and industrial process monitoring.