The cladding pumping within a double-clad fiber structure is an effective technique to convert high-power multimode beam into high-power. almost diffraction limited beam. Since the pump efficiency is limited by the presence of higher skew-ray modes. geometrical perturbations are used to scramble the modes and to achieve a higher overlap of the electromagnetic field with the doped core. https://www.jandroutboard.com/product-category/pull-along-toy/