An asymmetric Core-Offset optical fiber Mach-Zehnder interferometer based on CO2-Polished method for vector curvature measurement

In this paper, we propose an asymmetric fiber-optic Mach-Zehnder interferometer based on multimode fiber (MMF) and no-core fiber (NCF) for vector curvature sensing. The proposed sensor is fabricated by core-offset splicing using arc discharge and then CO 2 laser polishing of the core-offset region. The beam propagation method is employed to simulate the influence of different structural parameters on the transmission spectrum, thereby determining the optimal parameters. Based on these simulation results, experimental validation was conducted, which demonstrates that the proposed structure can distinguish between curvature applied along the + X, −X and Y directions with the maximum curvature sensitivities of −29.0 nm/m −1 , 10.9 nm/m −1 and 0.8 nm/m −1 , respectively. The different wavelength responses of the sensor under different bending directions arise from the asymmetry caused by core-offset and side polishing. With its high sensitivity, easy fabrication, and direction discrimination, the proposed sensor is promising for bridge health monitoring and aerospace material inspection.