Design of a Multiparameter Sensor Based on an Integrated Two-Cavity F-P Interferometer With G-PCF

Abstract

This paper proposes and experimentally demonstrates an all-fiber multiparameter sensor based on an integrated two-cavity Fabry-Pérot (F-P) interferometer. The sensing probe is fabricated by the controlled arc-discharge-induced fusion of a grapefruit-type photonic crystal fiber (G-PCF) and a single-mode fiber (SMF) to form an air microcavity, followed by the integration of a no-core fiber (NCF) and a polydimethylsiloxane (PDMS) coating at the distal end. The spectral modulation characteristics were evaluated across various cavity dimensions to optimize the structural parameters. The sensing mechanism is governed by three distinct dominant response mechanisms: gas pressure mainly drives the elastic deformation of the air microcavity; temperature variations induce PDMS volumetric expansion and alter the optical path length; and the ambient refractive index (RI) primarily modulates the amplitude of the distal Fresnel reflection. By extracting the envelope shift, fine-fringe shift, and fringe intensity, a complete cross-sensitivity matrix is constructed. Experimental results demonstrate the feasibility of simultaneous measurement of temperature, RI, and pressure with reduced cross-sensitivity, achieving sensitivities of 0.060 nm/$^\circ$C, 36.215 dB/RIU, and 3.591 nm/MPa, respectively. Benefiting from structurally separated response channels, this device provides a compact all-fiber platform for multidimensional state monitoring.