Intrinsic Fabry–Pérot Cavity Sensor Based on Etched Multimode Graded Index Fiber for Strain and Temperature Measurement

Two Fabry-Perot interferometers based on chemical etching in multimode graded index fibers are fabricated and their response to temperature and strain are compared. Chemical etching is applied in the graded index fiber end creating an air cavity. The interferometric cavity is formed when the graded index fiber with the air concavity is spliced to a single-mode fiber. The intrinsic sensors present high sensitivity to strain and low sensitivity to temperature. For the 62.5 μm core fiber, sensitivities of 6.99 pm/με and, 0.95 pm/°C were obtained for strain and temperature, respectively. The sensor based in the 50 μm core fiber, on the other hand, presented sensitivities of 4.06 pm/με and -0.84 pm/°C for strain and temperature, respectively.