Linearly chirped fiber gratings using uniform phase mask

A novel linearly chirped fiber grating was analyzed and fabricated by using uniform phase mask instead of chirped mask. The chirp of the grating is realized by precisely setting the distance between the fiber and the phase mask at every point of the fiber. The spectral characteristic and delay characteristic of such a chirped fiber grating were analyzed. And the influence on the grating by refractive index modulation variation caused by the variation of distance between the fiber and phase mask was also analyzed. In experiments we derived linearly chirped fiber grating by putting the fiber on the curved face behind the uniform phase mask to get ultraviolet light exposure. The fabricated chirped fiber grating has -1102 ps/nm dispersion, and time delay ripple of 17 ps. Gratings with different chirp with one uniform phase mask conveniently by only changing the curve function of the fiber, can be fabricated.