In this paper, an experimental device for a fiber-optic Mach-Zehnder sensor is designed and constructed, with the optimization of the design to obtain clear and stable spatial interference fringes. An independently designed peak-finding algorithm is implemented for high-precision fringe counting, enabling accurate counting even in the presence of external disturbances. The experimental device has a clear physical concept, intuitive physical phenomena, and rich experimental content. Students can observe the interference of multiple polarization states and the effect of polarization on fringe contrast by adjusting the polarization. They can also observe the effect of phase changes on fringe movement by adjusting the temperature of the semiconductor thermoelectric cooler or the voltage of the piezoelectric ceramic. Data acquisition and processing can be accomplished by students designing algorithms for measurement. The device is simple in structure, lightweight and compact, easy to adjust, low in manufacturing cost, and accurate in measurement, making it suitable for promotion and application in university physics laboratory teaching.