Fiber Bragg grating (FBG) offered by Precilasers is fabricated by ultraviolet lithography with phase mask. Through precise control of spectral shape and reflectivity, FBG pair formed by wavelength matched gratings with high reflectivity(HR) and low reflectivity(OC) is obtained. It can be used to make high-power CW and pulsed fiber lasers with excellent performance. The backward light at the HR end is effectively suppressed by optimizing the shape of the reflection spectra of the FBGs as well as strengthening the wavelength matching between HR and OC FBGs, so as to achieve the best efficiency and also increase the threshold of Raman scattering. FBG offered by Precilasers can be written on common single-mode fiber, large-mode area fiber, double-cladding fiber, polarization-maintaining fiber and other fibers. The characteristics such as wavelength, spectral width and reflectivity are flexible and can be customized to meet the requirements in many different fields.