提出了一种基于游标效应（VE）的极大倾角光纤光栅Sagnac干涉环折射率传感器。利用光学VE的基本原理，设计并制作自由谱宽为1.52 nm的保偏光纤Sagnac干涉仪和自由谱宽为1.36 nm的极大倾角光纤光栅Sagnac干涉结构，通过级联的方式将两个干涉光路进行叠加，得到游标光谱。实验结果表明，该传感器的游标包络特征明显，经游标放大后的折射率灵敏度达到-1286.40 nm/RIU，相比普通极大倾角光纤光栅传感器的横磁（TM）模和横电（TE）模的折射率灵敏度分别提高约8.46倍和约10.55倍，与理论计算结果吻合。传感器的输出光谱稳定，并且具有结构简单、制作方便、抗温度干扰能力较强等优点，在生化、生物医学检测等领域具有良好的应用前景。

An excessively tilted fiber grating (ExTFG) Sagnac interference loop refractive index sensor based on vernier effect (VE) is proposed. Utilizing the basic principle of the optical VE, a polarization-maintaining fiber Sagnac interferometer with a free spectral range (FSR) of 1.52 nm and a Sagnac interferometer composed of ExTFG with an FSR of 1.36 nm are theoretically designed and fabricated. The vernier spectrum is obtained by superimposing two optical paths by cascading. Experimental results show that the characteristics of the vernier envelope are easy to identify, and the refractive index sensitivity reaches -1286.40 nm/RIU through vernier amplification, improved ~8.46 and ~10.55 times than that of the TM and TE polarizations of the ExTFG sensors, respectively, which is in good agreement with the theoretically calculated result. The output spectrum of the sensor is relatively stable, and the sensor has the advantages of simple structure, convenient fabrication, and strong resistance of temperature crosstalk, leading to promising application in the fields of biochemical and biomedical detections.