Fiber Bragg Grating sensors one of the most requested fiber optic technologies have superior sensitivity and frequency specifications, making them well suited for many spheres of applications. The FBG inclinometers can be used to identify internal damage at a very early stage. The FBG inclinometers are devices used to monitor subsurface movements through sensors designed to measure inclination with respect to vertical. When installing the FBG inclinometer casing, it is important to select the appropriate diameter. The large-diameter casing is better suited to shear zones, multiple shear zones, and slope failures. Moderate- to small-diameter casing can be used for short-term installations or slopes where smaller displacements distributed along the borehole are anticipated. Correct installation of the casing is important; and deep holes, particularly the influence of helical deformation must be considered. A conventional FBG inclinometer system consists of a plastic casing that is installed in a nearly vertical position in the ground, with a servo-accelerometer or electro-level sensor inserted into the casing to measure the local tilt of the casing in response to ground movement. The sensor element is lowered and raised, guided by grooves in the inner surface of the casing, with the tilt of the casing being recorded at fixed spatial intervals.
Incline FBG sensors have been widely used to monitor ground movements in various applications, for example, landslides, tunnels, and foundations, etc., where they provide vital ground movement information including magnitude, rate, and location. The produced information can be used for checking design assumptions and provide early warning of problems.
Another type of FBG sensors that can monitor inclination is a tiltmeter. Tiltmeters are devices used to monitor the change in the inclination of a ground surface point. The device consists of a gravity sensing transducer capable of measuring changes in inclination as small as one arc second. They are used to monitor slope movements where the landslide failure mode is expected to contain a rotational component. The advantages of using tiltmeters are their lightweight, simple operation, and relatively low cost. They may be combined with an incline FBG sensor and extensometers in what has been termed as integrated pit slope monitoring systems.