Temperature-insensitive two-dimensional tilt sensor based on cylindrical pendulum and FBGs

We propose a temperature-insensitive two-dimensional (2-D) tilt sensor based on a cylindrical pendulum and Fiber Bragg Gratings (FBGs). Three FBGs are fixed on the cantilever beam structure, and the included angle between them is 120°. The central wavelength of the FBG reflection spectrum drifts under pressure, and the inclination angle can be measured by monitoring the drift. The relationship between the stress and the deformation of the tilt sensor is obtained by finite element simulation, then the optical fiber tilt sensor is calibrated and tested. The experimental results show that the tilt sensitivity of the three FBGs of the sensor is 19.83 pm/°, 20.26 pm/°, and 20.04 pm/°, respectively. The temperature sensitivity is 35.8 pm/°C, 36.79 pm/°C, and 36.24 pm/°C, respectively. The measurement error is ± 0.2° within the range of ± 15° of deflection angle, and ± 0.55° within the range of 0°–360° of direction angle. And the sensor is inherently insensitive to temperature. This tilt sensor has the advantages of simple structure, small transmission loss, self-compensation of temperature, and long-distance transmission, and has broad application prospects.