High Sensitivity Optical Fiber FP Interferometer Based on Vernier Effect for Temperature Sensing

A temperature sensor based on fiber Fabry Perot interferometer (FPI) is proposed and demonstrated, which is composed of hollow core fiber (HCF) and cascaded multimode fiber (MMF). The optical Vernier effect is successfully realized through FP cavities with different lengths of HCF and MMF, and the temperature sensitivity is significantly improved. The temperature sensitivity of 69.2 $\text{pm}/^{\circ}\mathrm{C}$ is achieved by detecting the generated spectrum envelope through the FPI's spectrum. A high sensitivity optical fiber temperature sensing system with low complexity, good linearity, short response time, and low cost can be realized with the proposed method.