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.