This work presents the implementation of an optical system for fiber Bragg grating writing by using the phase mask technique. The method consists of radiating a photosensitive optical fiber with a suitable intensity pattern of UV light that generates a spatial modulation of the fiber core refraction index and creates the Bragg grating. As light source a beam of an Nd-YAG pulsed laser, of quadrupled frequency, and 266 nm emission, was used. The proposed system is described, the results are analyzed, and applications developed with fiber Bragg grating are mentioned.