Highly sensitive optical fiber pressure sensor based on the FPI and Vernier effect via femtosecond laser plane-by-plane writing technology.

In this paper, a highly sensitive pressure sensor based on fiber-optic Fabry-Perot interferometers (FPIs) and the Vernier effect (VE) is proposed and experimentally demonstrated. We employ a closed capillary-based for the sensing cavity, and an created through femtosecond laser refractive index modulation for the reference cavity, which remains impervious to pressure changes. Connecting these two FPIs in series produces a VE-based cascaded sensor with a clear spectral envelope. The femtosecond laser micromachining technique provides precise control over the length of and facilitates adjustments to the VE's amplification degree. Experimental results reveal significant pressure sensitivities of -795.96 / and -3219.91 / , respectively, representing a 20-fold and 80-fold improvement compared to (-39.80 / ). This type of sensor has good sensitivity amplification and, due to its all-fiber structure, can be a promising candidate for high-temperature and high-pressure sensing, especially in harsh environments.