FBG Mirrors are based on the reflective properties of the Fiber Bragg Grating (FBG) written in the core of an optical fiber waveguide. FBG mirrors’ principal application is to use a high and low reflector to form a stable laser cavity having the lasing wavelength selected by the low reflector. Fiber Bragg grating (FBG) is a distributed reflector constructed in an optical fiber short segment that allows reflecting particular wavelengths and transmitting the rest of them. The periodic variation of the fiber core refractive index generates a wavelength-specific dielectric mirror, which allows reflecting specific wavelengths. FBG can be used as a high reflector (HR) and output coupler (OC) to make a laser cavity in a fiber laser. Rare earth doped optical fiber increases the laser gain.