Highly sensitive gas pressure sensor utilizing the harmonic vernier effect in parallel FPIs with femtosecond laser processing

This work proposes and prepares a high-sensitive fiber optic gas pressure sensor based on the first harmonic vernier effect (FHVE). It has two parallel Fabry-Perot interferometers (FPI), each made of a single-mode fiber and a small segment of capillary tube fused as a sensing cavity and a reference cavity, and the end face of the sensing cavity is cut into a thin slice with a femtosecond laser pulse to make it sensitive to gas pressure. When the sensing cavity's (FPI1) and reference cavity's (FPI2) free spectral ranges are close to each other, a traditional vernier effect occurs, and the gas pressure sensitivity approaches 58.49 nm/MPa, which is approximately 14.64 times that of the single sensing cavity (FPI1). When the free spectral range of the sensing cavity (FPI1) is roughly twice that of the reference cavity (FPI3), the first harmonic vernier effect is observed. This leads to a significant in-crease in gas pressure sensitivity, up to 141.80 nm/MPa, which is about 35.45 times higher than what a single sensing cavity (FPI1) would achieve. Furthermore, testing results reveal that the sensor is temperature insensi-tive, with a low cross-sensitivity of 3.1 x 10-5 MPa/degrees C for gas pressure to temperature. This device is made of pure quartz glass, has high mechanical strength, a sealed construction, is easy to fabricate, has a high sensitivity of gas pressure, and may be used to monitor pressure in extreme conditions such as offshore oil or underwater operations.

Automated summary

This work proposes and prepares a high-sensitive fiber optic gas pressure sensor based on the first harmonic vernier effect (FHVE). The sensor has two parallel Fabry-Perot interferometers (FPI) made of single-mode fibers and capillary tubes. The end face of the sensing cavity is cut with a femtosecond laser pulse to enhance gas pressure sensitivity. The sensor achieves a high gas pressure sensitivity and is temperature insensitive, making it suitable for monitoring pressure in extreme conditions.