Highly sensitive air pressure sensor based on harmonic Vernier effect by Fabry-Perot and Sagnac interferometers cascading

Abstract

A high sensitivity harmonic Vernier effect air pressure sensor is proposed based on Fabry-Perot interferometer (FPI) and Sagnac interferometer (SI) cascading. FPI consists of an F-P cavity with micro-pore, detecting the changes of environmental air pressure. The reference interferometer SI is composed of panda fiber rings and cascaded with FPI to generate a harmonic Vernier effect. In harmonic Vernier effect sensor, using inner envelope intersection to measure air pressure can achieve more accurate sensitivity and measurement accuracy. Meanwhile, the harmonic Vernier effect has lower requirements for free spectral range matching between two interferometers, making it easier to achieve harmonic Vernier effect and its sensitivity is i + 1 times that of the fundamental Vernier effect. The sensitivity of the first-order harmonic Vernier effect sensor obtained in the experiment is 132.32 nm/MPa, while the corresponding the fundamental Vernier effect sensor has the sensitivity of only 68.78 nm/MPa, almost doubling. The experimental results also confirm that the proposed sensor has excellent long-term stability and repeatability. Meanwhile, the temperature cross-sensitivity of the proposed air pressure sensor is only 0.0124 MPa/°C, which is small. This sensor is expected to play a crucial role in precise and highly sensitive air pressure measurement applications.