Optical fiber sensors

Optical fiber sensors can be incorporated into a structure at the time of fabrication for structural health monitoring and they can be utilized for knowing the state of the structure on continuous basis and indicating the adverse changes in the structure such as initiation of crack and growth of defects. Fiber Bragg Grating (FBG) sensors are the most popular optical fiber sensor. FBGs are diffraction gratings which are written into the core of a single mode fiber using interfering lasers. The grating reflects light at a particular wavelength which can be measured by analyzing the spectral response [Figure 7.1].

Figure 7.1: Working basis of fiber optic sensors

A change in spacing of grating and shift in its characteristic wavelength is observed in the presence of longitudinal strain or temperature variations.