Fujikura's FBG (Fiber Bragg Gratings) are manufactured by forming periodic refractive index variations on the core of an optical fiber through ultraviolet light irradiation. FBGs exhibit reflection and transmission characteristics for specific wavelengths, functioning as mirrors. A fiber Bragg grating (FBG) is a type of distributed Bragg reflector constructed in a short segment of optical fiber that reflects particular wavelengths of light and transmits all others. Typically, the perturbation is approximately periodic over a certain length of e.