Ultra-high-sensitivity gas pressure sensor based on a cascaded Fabry-Perot interferometer and the Vernier effect

Subject of study. An ultra-sensitive gas pressure sensor based on a cascaded Fabry-Perot interferometer is proposed. Purpose of the work. In the proposed sensor, we greatly improve the gas pressure sensitivity of the sensor by using the optical Vernier effect method. Method. During the fabrication of the sensor, one Fabry-Perot interferometer is used as the sensing interferometer, and the other Fabry-Perot interferometer is used as the reference interferometer. Both Fabry-Perot interferometers are fabricated by two sections of single-mode fiber spliced at both ends of a section of a quartz capillary. Then, a micro-hole is drilled in the capillary wall of the sensing Fabry-Perot interferometer by using femtosecond laser micro-processing technology for gas pressure measurement. When the free spectral ranges of two Fabry-Perot interferometers are similar, the optical Vernier effect will be generated by cascading them. By precisely controlling the cavity length difference between two Fabry-Perot interferometers, a very high sensitivity magnification factor can be obtained. Main results. The experimental results show that the sensitivity of the Vernier effect sensor is 133.2 nm/MPa in the pressure measurement range of 0–0.8 Mpa, which is 33.3 times higher than that of the single sensor Fabry-Perot interferometer. In addition, the temperature cross-sensitivity of the sensor is relatively small, only 0.93 kPa/°C. The sensor is flexible in design and easy to manufacture and operate. Practical significance. The proposed sensor has extremely high gas pressure sensitivity, and it can be used in the fields of chemical production, pharmaceuticals, oil and gas storage, and environmental protection for high-sensitivity gas pressure measurement.