Fiber Bragg Grating Sensor (FBG)
By making grating inside core of fiber optic, such grating shall reflect particular wavelength of laser, correlating to period of grating. Grating period expands or shrinks to strain and temperature change.
To fabricate a FBG, photosensitive fiber is exposed to high intensity ultraviolet light, forming a periodic change in the refractive index of the fiber's core. This pattern, or grating, reflects a particular wavelength of light that is dependent upon the period, Λ, of the refractive-index profile formed in the core. In its most basic operation as a sensor, the modulation index within of the FBG is altered by an external stimulus, resulting in a shift in the wavelength reflected by the FBG. By measuring the shift in reflected wavelength, the external stimulus can be determined.