An Omni-Azimuth Angle Sensor for Tilt Measuring Based on FBG Array

An omni-azimuth angle sensor for tilt measuring based on fiber Bragg grating (FBG) array is proposed. It is designed based on the sensitivity of FBG to axial traction. The sensor consists of a mass block and a cube frame connected by an FBG array. The FBG array consists of four FBGs. When the sensor is tilted at different angles, the axial traction of each FBG will change due to the pull of the mass block. The tilt angle of the sensing unit can be obtained by calculating the magnitude and direction of the resultant traction of the four FBGs. The array design and measurement theory of the sensor are introduced, and the sensitivity of the sensor is discussed. Experimental results show that the FBG array can be used to measure the omni-azimuth angle. The angle sensitivity varies unevenly with the tilt angle and the range of variation is 0.08 nm/° to 0.4593 nm/°. Using the spectrometer with an accuracy of 0.01 nm, the angle resolution ranges from 0.125° to 0.0218°. The array effectively extends the measurement range of the tilt sensor, and reduces the number of FBGs as much as possible on the basis of achieving omni-azimuth angle measurement.