Three-Dimensional Low-Frequency Earthquake Monitoring Vibration Sensor Based on FBG

Fiber Bragg grating (FBG) vibration sensors exhibit promising application prospects in complex environmental fields such as earthquake, tsunami, and coal mine vibration monitoring. In response to the challenge of effectively capturing low-frequency vibration signals using existing FBG sensors, this study proposes a specialized 3-D low-frequency FBG vibration sensor designed for earthquake monitoring. Initially, the study established a composite elastic structural model of cross reeds and cantilever beam elastomers to pick up low-frequency signals effectively. Subsequently, this study utilizes a differential evolution genetic algorithm to achieve global results under multiple constraints of composite structures. Finally, the research involves processing and packaging the sensor to ensure sensor stability. The experimental outcomes reveal that the sensor maintains a stable range between 0.1 and 20 Hz, exhibiting a minimum detectable frequency of 0.01 Hz and a sensitivity of 606.2 pm/g. The sensor achieves a transverse sensitivity ratio of 2.3%, with a dynamic resolution exceeding 0.173 mg/Hz $^{1/2}$ within the stable range and a dynamic range of 81.9 dB, exhibiting satisfactory sensitivity and precise angular characterization. The sensor has excellent temperature compensation and creep resistance. The insights derived from this research offer substantial promise for advancing low-frequency vibration monitoring in various complex environmental contexts.