Cascadable four-core fiber-Bragg gratings accelerometer for 2-dimension low-frequency vibration measurement

A two-dimensional (2D) vector vibration sensor is designed and fabricated by using an optical fiber double-clamped beam with four-core fiber Bragg gratings and a mass block which is glued in the middle of fiber. Vectorial acceleration perpendicular to the fiber can be measured using two mutually orthogonal FBG-pairs in the four-core fiber to obtain the 2D vibrating information. The experimental results show that the sensor possesses a 2D vectorial acceleration sensitivity of 345 pm/g in the flat response region of 5-30 Hz, and it is temperature insensitive, compact, and cascadable. Both resonance frequency and sensitivity can be improved by optimizing the length and weight of the free-fiber. The proposed sensor has the potential applications for dynamic monitoring in oil exploration, seismic exploration, heart rate monitoring.