A Multi-Azimuth Angle Sensor for Tilt Measuring Based on LPFG Array

A multi-azimuth angle sensor for tilt measuring based on long period fiber grating (LPFG) array is proposed. It is designed based on the sensitivity of LPFG to refractive index. The sensor consists of a sealed cylindrical device containing a half volume NaCl solution. The LPFG array which consists of four mutually perpendicular LPFGs is fixed in the container. When the sensor is tilted at different angles, the liquid level intersects with the LPFGs at different positions. By calculating the intersection point of liquid level and LPFGs, the liquid level equation after tilt can be obtained, and the tilt angle can be obtained. The array design and measurement theory of the sensor is presented, and the sensitivity of the sensor is discussed. The experimental result shows that the LPFG array can be used to measure multi-azimuth angle in tilt. The angle sensitivity varies unevenly with the tilt angle, and the range of variation is 0.0006nm/° ~ 0.0434 nm/°. The array expands the measurement range of the tilt angle sensor effectively.