提出一种基于夹层多模光纤马赫-曾德尔干涉仪（MZI）与虚拟游标效应结合的高灵敏度温度传感器，进行了理论分析和实验验证。该光纤MZI是通过在两段1 mm长的阶跃型多模光纤之间拼接一段20 mm的渐变多模光纤制成，夹层多模光纤MZI作为游标效应的传感干涉仪，利用信号处理对该光纤MZI的干涉光谱进行变频得到参考干涉仪光谱，通过叠加传感干涉仪和参考干涉仪的波形实现虚拟游标光谱。实验结果表明，在40~100 ℃温度范围内，该传感系统的温度灵敏度为3.884 nm/℃，与单个夹层多模光纤MZI相比，灵敏度提高了37.346倍。与传统的光纤游标传感器相比，所提出的虚拟游标夹层多模光纤温度传感器具有灵敏度极高、尺寸紧凑、制作简单、成本低、结果更可靠等优点。

In this study, a high-sensitivity temperature sensor based on the sandwich multimode fiber Mach-Zehnder interferometer (MZI) with the virtual vernier effect is developed, and theoretical analysis and experimental verification are performed. The MZI was made by splicing a graded-index multimode fiber with a length of 20 mm between two pieces of stepped-index multimode fibers with lengths of 1 mm. The sandwich multimode fiber MZI was used as the sensor interferometer to evaluate the vernier effect, and the reference interferometer spectrum was obtained via frequency conversion of the interference spectrum of the fiber MZI through signal processing. The virtual vernier spectrum was obtained by superimposing waveforms of the sensing and reference interferometers. The experimental results show that the temperature sensitivity of the sensor system is 3.884 nm/℃ within the temperature range of 40-100 ℃, which is 37.346 times higher than that of a single-sandwich multimode fiber MZI. Compared with the traditional fiber sensors based on the vernier effect, the proposed sandwich multimode fiber MZI temperature sensor based on the virtual vernier effect has exceptionally high sensitivity, compact size, simple fabrication, low cost, and more reliable results.