Cascadable Four-Core Fiber Bragg Gratings Accelerometer for 2-D Low-Frequency Vibration Measurement

A 2-D vector vibration sensor is designed and fabricated by using an optical fiber double-clamped beam with four-core fiber Bragg gratings (FBGs) and a mass block that is glued in the middle of the fiber. Vectorial acceleration perpendicular to the fiber can be measured using two mutually orthogonal FBG-pairs in the four-core fiber to obtain the 2-D vibrating information. The experimental results show that the sensor possesses a 2-D 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 potential applications for dynamic monitoring in oil exploration, seismic exploration, and heart rate monitoring.