Fiber Optic Strain Sensors Technology and Applications

Nowadays, different types of fiber optic strain sensors have attracted attention from all over the world. Fiber Bragg Grating (FBG) has become the most widespread technique, directly applicable to bridges, concrete, and dams for strain measurement.

To create the actual strain sensor, the optical fiber is inscribed during production with a Fiber Bragg Grating (FBG). This is basically a pattern of material interferences, which reflects the light differently from the rest of the fiber. For better understanding, visualize the fiber as a cylindrical length of transparent material, with a number of thin slices in it. When the light from the laser hits this pattern, certain wavelengths are reflected, while others pass through.

The material interferences are placed at certain intervals. When the fiber is stretched or compressed and is therefore subjected to positive or negative strain—these intervals change. When the fiber is stretched, it lengthens and the spaces get bigger and vice versa. Not only does the reflected light take a little longer or shorter to travel back when the Fiber Bragg Grating is under strain, but the wavelength that is reflected also changes. In scientific terms, the Fiber Bragg Grating has a certain refractive index. The refractive index of a material describes how much light is bent or refracted when passing through the material. When the grating changes shape due to strain, its refractive index changes as well.

For measurements, the optical fiber needs to be connected to a so-called interrogator; it continuously sends out light in different wavelengths, one at a time, thus covering a wide spectrum.  In order to ensure the safety of personal and public property, the precise and real-time monitoring of strain becomes more and more important in all kinds of engineering applications, such as chemical plants, gas stations, power stations, bridges, tunnels, oil pipelines, etc.. In general, these application environments full of poisonous gas, intense radiation, and elevated temperature are dangerous to human health, so safe and efficient remote monitoring of strain is of great significance. Compared with conventional electrical sensing methods, an optical fiber strain sensor is more suitable for present applications because of its compact size, high sensitivity, multiplexing capability, immunity to electromagnetic interference, high-temperature tolerance, and resistance to harsh environments.

Fiber optic strain sensors are welded directly to the surface of the metal structure (pipes, beams, etc.), and it has a protective silicone cover. Fiber optic strain sensors are durable and stable, widely used for civil engineering constructions, particularly they reinforce concrete structures exceptionally well.

If you would like to purchase Optromix FBG Strain Sensors, please contact us: info@optromix.com  or +1 617 558 98 58