According to one aspect, a few-mode amplifying fiber in a given spectral band of use is provided. The few-mode amplifying fiber comprises a cladding having a given refractive index (n0) and at least one core of refractive index and of dimensions suited to the propagation of a finite number of spatial modes in the spectral band of use of the fiber, a spatial propagation mode corresponding to a channel for transporting information. The core comprises a first solid material having a given first refractive index (n1) strictly greater than the refractive index of the cladding (n0), and, within said first material, inclusions spatially separated from one another, formed by longitudinal bars comprising a second solid material having a second refractive index (n2) strictly greater than the first refractive index (n1), at least one of said inclusions being actively doped.