(57) Abstract: The Yb to produce a doped double-clad active fiber fiber laser (106), for writing a first Bragg grating near the first end (114a) suitable pre-treated to facilitate the acceptance of UV radiation, in the writing process, the scanned pumping radiation is supplied to the first end of the active fiber, and the first diffraction grating, pre cutting excites the amplified stimulated emission between the reflecting surface of the second end portion of the washed activated fiber (114 b), the result of laser emission is induced from the active fiber as, the laser emission measuring the light output, to obtain a laser efficiency is treated, if the efficiency reaches the maximum value, to stop the writing process. Writing the second diffraction grating near the second end portion (114b) of the active fiber by using the same steps.