Rubber-Based Diaphragm FBG Geophone: Effect of Variable Diameter, Mass, and Thickness

Measuring low-frequency signals is essential for comprehensive monitoring in oil and gas fields as well as for structural health assessments. This article introduces a cutting-edge fiber Bragg grating (FBG) geophone with a rubber-based diaphragm structure. The structure performance was evaluated by varying diameters from 25 to 55 mm, thickness from 0.8 to 1.4 mm, and mass from 0.1 to 3 gm. The present study aims to achieve the highest vibrational sensitivity and the lowest natural frequency. Diaphragm diameter and mass exhibited a direct correlation with sensitivity while showing an inverse relationship with the sensor’s natural frequency. In the seismic frequency range of 5–30 Hz, the optimal parameters for the rubber-based diaphragm were identified as a mass of 1 gm, a thickness of 1 mm, and a diameter of 45 mm, yielding a sensitivity of 89.44 pm/g, and a natural frequency of 39.39 Hz. At these parameters, the temperature sensitivity was also 15.67 pm/°C. The error in sensitivity and natural frequency between the finite element analysis (FEA), experimental results, and theoretical modeling was less than 10%, highlighting the high predictability of the FEA, and experimental model with theoretical modeling. A geophone with this type of performance has significant potential for advancing low-frequency seismic exploration within the oil and gas industry.