An FBG Vibration Sensor Tailored for Monitoring Ultralow-Frequency Vibration Signals

Monitoring low-frequency and ultralow-frequency (
$0.01\sim 20$
Hz) vibration signals is crucial for various engineering structures and projects, including rotating machinery, bridges, dams, marine platforms, nuclear power plants, and seismic research. To address the limitations of conventional fiber Bragg grating (FBG) sensors in detecting 0.01 Hz vibrations, a novel FBG sensor with a dual-spring leaf structure is proposed. The sensor’s dynamic response formula is established, and the influence of structural parameters on sensitivity and natural frequency is analyzed. Simulation analysis is conducted to determine static stress and modal characteristics, followed by performance testing using an ultralow-frequency vibration test system. Results show that the proposed sensor can effectively monitor vibration signals in the 0.01–20 Hz frequency range with a natural frequency of 50 Hz. In addition, it demonstrates displacement sensing capabilities in the 0.01–1 Hz frequency band, providing valuable insights for similar sensor designs.