Highly Sensitive FBG Seismometer With a 3D-Printed Hexagonal Configuration

We have designed and developed a compact fiber optic accelerometer for vibration detection. The mechanical vibrating element is a hexagonal structure which is fabricated using 3D-printing technology. Such a structure can efficiently convert vertical vibrations into periodic deformations of a longitudinally positioned fiber structure into which a fiber Bragg grating (FBG) is inscribed. By demodulating the wavelength shift of the reflection spectrum, we established the relationship between vibrational acceleration and wavelength shift. The measured sensitivity is 421.4pm/g. A second FBG inscribed in the fiber enables temperature compensation. The proposed design has achieved a working bandwidth from 10 to 210Hz with a resonant frequency of 124.9 Hz. Both laboratory and in-field measurements using our sensor have been compared with those of a traditional electromagnetic accelerometer to validate the effectiveness of the derived theoretical models and the simulation results. The comparison has effectively supported the parameter determination of the sensor design.