The far-field intensity pattern of a light beam with a defined value of orbital angular momentum is analyzed theoretically and experimentally. Using numerical simulations of a wave plane diffracted through of a hologram with fork shape, we calculate the mean radius of the inner ring for beams with integer orbital angular momentum in the Fraunhofer regime. For beams with non integer orbital angular momentum, we study the rotation on the far field intensity pattern diffracted produced by the dislocation phase over the fork hologram. Additionally, experimental results are presented for the far field diffraction pattern for beams with integer OAM and non-integer OAM, product of an electromagnetic wave incident on a fork hologram written on a spatial light modulator.