Elastic Plate-Coupled Dual FBG Configuration Enabling High-Sensitivity Fiber-Optic Accelerometer with Wide Frequency Range

Vibration sensing plays a pivotal role in structural health monitoring of civil infrastructures. This paper presents a novel Fiber Bragg Grating (FBG) based accelerometer employing an elastic plate-coupled dual-FBG configuration, designed to achieve high sensitivity (56.5 pm/G) and broadband operation (30-800 Hz) while inherently suppressing temperature crosstalk. By placing a mass between two cascaded FBGs, the two gratings experience tensile and compressive strain individually during vibration, which enhances the sensitivity for a given acceleration and eliminates the temperature effect simultaneously. A theoretical model based on the geometrical design of the accelerometer is deduced and simulated based on finite element analysis (FEA) to achieve optimal parameters. A parametric finite element model integrating modal analysis and amplitude-frequency response simulations guides the optimization of resonant frequency (1262 Hz calculated vs. 1200 Hz experimental) and strain distribution. Experimental validation demonstrates <5% deviation between simulated and measured frequency responses, with robust transverse interference resistance (<8% cross-sensitivity). The central wavelength drift of the fiber Bragg grating demonstrates good linearity and stability in response to acceleration. The proposed FBG accelerometer offers significant advantages over existing designs, particularly in applications requiring wide operational frequency bands and high sensitivity.