Biaxial 3D-Printed Inclinometer Based on Fiber Bragg Grating Technology

A Fiber Bragg Grating (FBG)-based inclinometer has been developed for field use, designed to incorporate biaxial 3-dimensional (3D) printed tilt sensors (in which four FBGs were used). The inclinometer was characterized by examining its response to a wide range of tilts, over the range from 0° to 90°, towards the inclination axes. An excellent linear correlation between the wavelength shifts and the inclination angle (up to the 90° used) was obtained, showing an average sensitivity of 0.01 nm per degree of inclination angle, for each of the FBGs used. In addition to the four FBGs that form the basis of the inclination measurement, a further FBG was included in the design to allow compensation for any temperature changes experienced during the measurements. The device was calibrated over the range from −25°C to 80°C (corresponding to the extremes of cold and hot weather conditions likely to be experienced in-the-field), and a sensitivity to temperature change of 0.011nm/°C was achieved, allowing an effective temperature correction to be applied. The data obtained from a full characterization of the performance of the sensor system, carried out in a stable, controlled environment, indicate that this inclinometer yields good sensitivity, making it highly applicable for use in monitoring rapid ground movements and deformations with its compact design allowing its wide use.