Inclination Sensor Based on FBG with Enhanced Sensitivity

The Brazilian mining disaster, which occurred in 2015 in the city of Mariana, released millions of tons of toxic mud and has caused destruction across a vast area from the mountains of Minas Gerais to the Atlantic Ocean. Preventing such accidents demands a real-time, continuous monitoring sensor system capable of detecting dangerous soil displacement. In this paper, we present a temperature-independent, modular inclinometer based on a fiber Bragg grating (FBG) array for the detection of soil displacement. The proposed sensor array is based on a modular topology, in which each module is composed of a pair of FBG sensors bonded to the opposite sides of a steel cantilever holding a known weight. When the system is inclined, the gravitational force acts on the weight, pushing the cantilever to a bending position. Furthermore, since the measurements are wavelength-encoded, the proposed sensor does not suffer from light source intensity fluctuations. Our prototype was tested in laboratory with inclinations ranging from 0 degrees to 40 degrees with a resolution of +/- 0.025 degrees and very good repeatability, indicating that the proposed system is feasible and can be applied to the precise and fast detection of soil displacements.