为了实现温度和应变同时测量，本文设计了一种基于多模干涉的光纤温度和应变传感器.该传感器利用光纤熔接机将一段细保偏光纤和一段细芯光纤错位熔接后引入萨格纳克环中而制成.由于光纤错位和模场失配，传感器内存在偏振模干涉和纤芯模-包层模干涉.对不同温度和应变作用下采集到的传感器透射谱进行滤波处理，可提取两种干涉对应的透射谱.基于透射谱中两个不同波谷的温度和应变灵敏度建立同时测量矩阵，即可实现温度和应变的同时测量.实验数据显示该传感器的温度和应变分辨率分别为0.30 ℃和13.50 με.本实验可以作为物理和光电相关专业本科生物理创新实验，帮助大学生掌握光纤传感原理、实验技能和数据处理与分析方法.

In order to achieve simultaneous temperature and strain measurement, in this paper, a fiber optic temperature and strain sensor based on multi-mode interference is proposed. The sensor is fabricated by splicing a section of thin polarization maintaining fiber and a piece of thin core fiber in a Sagnac loop with a fiber fusion splicer. Interference between polarization modes and core mode-high cladding modes exist in the sensor due to fiber offset and mode field diameter mismatch. The transmission spectra corresponding to the two types of interferences under different temperatures and strains are extracted by a low pass filter. The simultaneous temperature and strain measurement are validated by building a matrix through the temperature and strain sensitivities of two selected dips in transmission spectra. Experimental results show that the temperature and strain resolutions are 0.30 ℃ and 13.50 με, respectively. This experiment can be used as an innovative physics experiment for undergraduates majoring in physics and optoelectronics to help them master the principles of optical fiber sensing, experimental skills, and data processing and analysis methods.