Optical guide including nanoparticles and manufacturing method for a preform intended to be shaped into such an optical guide

The invention relates to an optical fiber comprising a gain medium which is equipped with: a core which is formed from a transparent material and nanoparticles comprising a doping element and at least one element for enhancing the use of said doping element; and an outer cladding which surrounds the core. The invention is characterized in that the doping element is erbium (Er) and in that the enhancing element is selected from among antimony (Sb), bismuth (Bi) and a combination of antimony (Sb) and bismuth (Bi).According to the invention, one such fiber is characterized in that the size of the nanoparticles is variable and is between 1 and 500 nanometers inclusive, and preferably greater than 20 nm.