Fiber Bragg grating displacement sensors are surface-mounted and detect the distance between two anchor points. On top of that, they can track extension and compression displacement. With the development of fiber optical technologies, fiber Bragg grating (FBG) sensors are frequently utilized in structural health monitoring due to their considerable advantages, including fast response, electrical passivity, corrosion resistance, multi-point sensing capability and low-cost. Fiber Bragg Grating (FBG) sensors are the best choice for harsh environmental conditions and often used as an alternative to traditional ones. They provide several benefits, for example to make precise measurements and to capture events at extremely high speeds. This review provides a comprehensive overview of FBG sensor technology.