The present invention relates to a method for manufacturing a multimode optical fibre having a refractive index profile, wherein doped or undoped glass layers are deposited on the interior of a substrate tube by means of a chemical vapour deposition technique, using a reactive gas mixture, so as to obtain a preform having a precisely defined refractive index profile, from which preform of a multimode optical fibre is drawn by heating one end of the perform. At least concentration of one refractive index modifying dopant at a light-guiding core of the multimode optical fibre is modified, so that the concentration of the modifying dopant at the central fibre axis (r=0) is lower than that at the light-guiding core area. The present invention also relates to a multimode optical fibre having arefractive index profile, comprising a light-guiding gradient index core built up from a number of dopant, wherein at least concentration of one refractive dopant of the light-guiding core of the multimode optical fibre is modified, so that the concentration of the dopant at the central fibre axis (r=0) is lower than that at the light-guiding core area.