High-sensitivity fiber gas pressure sensor based on the Vernier effect generated by femtosecond laser-inscribed micro-cascaded FPIs

We demonstrate a Vernier effect-enhanced all-fiber gas pressure sensor with an extremely simple structure. The sensor consists of a rectangular air cavity near the end face of a single-mode fiber (SMF) fabricated by femtosecond laser micromachining. The two walls of the air cavity and the end face of the SMF form micro cascaded Fabry–Perot interferometers to generate the Vernier effect. The sensor exhibits a gas pressure sensitivity of 79.69 nm/MPa within a range of 0.1–2.5 MPa, an ultralow temperature cross-sensitivity of 0.0002 MPa/°C, and excellent stability. Owing to its straightforward fabrication and outstanding performance, the sensor holds significant potential for mass production and application in confined spaces for high-precision gas pressure monitoring.