A Fiber Bragg Grating Force Sensor with Sensitization Structure

This article presents a fiber Bragg grating (FBG) force sensor with enhanced sensitivity. a strain-reinforcing mechanism comprised of a linear structure and loop-shaped structure is proposed. When external tension is applied, the strain directions are opposite in the two structures. Two FBGs were adhered to the surfaces of positive and negative strain bodies and sensor data were compared. Then, the sensing principle of the FBG force sensor was deduced based on the theory of material mechanics. Results of theoretical calculations and finite element analysis (FEA) show that sensitivity of the proposed sensor is about 5.07 times higher than an FBG directly adhered to the surface of the substrate. Comprehensive testing of the sensor prototype was conducted. Experimental results show that the sensor can achieve a sensitivity of 38.25 pm/kN with a repeatability error and hysteresis error of 2.11% and 1.76%, respectively. The enhanced coefficient is 4.84, which is basically consistent with theoretical design value of 5.07. In addition, favorable temperature compensation and creep resistance were obtained during performance tests. Good capability for alternating strain measurement has also been demonstrated. Our results demonstrate the potential for superior structural health monitoring in civil engineering applications using the proposed sensor structure.