Fiber Bragg grating biaxial tilt sensor using one optical fiber

Fiber Bragg grating (FBG) biaxial tilt sensors used to use two optical fibers and four FBGs to measure inclination in two perpendicular directions, whereas here we have demonstrated one using one optical fiber and two FBGs. The inclination along the direction of the fiber (axial direction) can be distinguished by the difference of the resonant wavelengths of the two FBGs, and the inclination in the transverse direction distinguished by the average of the resonant wavelengths of the two FBG. In the experiments, from −50° to 50° in the axial direction, the difference changed linearly with inclination, R2=0.998, and the sensitivity was 1.1pm/°; from 20° to 70° in the transverse direction, the average changed linearly with inclination, R2=0.902, and the sensitivity was 4.5pm/°. The mass of the inertial object was 5.3g. The detailed theoretical and experimental results are in the supplementary material.