Electrical Strain Gauges for Infrastructure - Fiber Bragg Gratings (FBGs) are optical sensors that measure strain by reflecting a specific wavelength of light, which shifts under strain, offering advantages such as immunity to electromagnetic interference and. Optical Fiber vs. They are very well suited to the new materials of glass and carbon fiber reinforced composites which are often used for highly stressed constructions, e. Strain gauges use electrical resistance changes, while FBGs rely on wavelength shifts in optical fibers to detect strain with high sensitivity and. Optical sensors based on Fiber Bragg Gratings (FBG) are becoming increasingly popular.