This paper provides a systematic introduction to the principle of FP cavity fiber optic sensors based on thin film technology and reviews the applications and development trends of this sensor in various measurement fields. Fiber sensors possess characteristics such as compact structure, simplicity, electromagnetic interference resistance, and reusability, making them widely applicable in various practical engineering applications. Keywords: fiber-optic sensor, Fabry–Perot cavity, peak-to-peak method, zero-cross detection 1. An integrated fiber Bragg grating (FBG) was included to monitor. A fiber-based Fabry–Perot (FP) optical sensor is well-suited for the rapid and selective detection of gas molecules, including volatile organic compounds (VOC), explosive analytes, etc.