FBG mirrors are based on Raysung’s proprietary Double-Clad FBG technique, where the wavelength difference between the high reflection cavity mirror (HR) and the output coupler (OC) can be controlled at +/-0.1 nm accuracy. With the special heat management technique of FBGs, the FBGs meet to the highest standards of reliability and performance needs. For fiber laser developers working with a 10/125 or 20/400 fibers, the common design parameters are HR: > 99% reflectivity, 2 nm or 3 nm FWHM and OC: 5% or 10% reflectivity, 0.5 nm or 1 nm FWHM.