Transmissionsfiber med optisk forstærkning og fremgangsmåde til fremstilling af den

A transmission fibre (1; 5) with optical amplification, comprising a core (2) and a cladding (3). The core material is doped with a first dopant (A) of a material having a higher index of refraction than the material of the cladding (3) and with a second dopant (B) of a material that converts pump energy in the form of light having a first wavelength into light having a second wavelength. The concentration of the second dopant (B) within the core (2) increases in radial direction (r) in proportion to the distance to the centre of the core (2). The core material is preferably doped with a third dopant (C) for compensating the variation in the refractive index caused by the second dopant (B). The cladding (3) may comprise a cladding layer (4) surrounding the core (2) provided with a fourth (D) and a fifth dopant (E) for signal amplification and refractive index compensation, respectively, in the cladding layer (4). The dopants (A, B, C, D, E) have been selected to enable amplification, using the Raman effect or stimulated emission.