Patent ID: 7483611

Claim:
A transmission fibre with optical amplification, comprising a core and a cladding, wherein the core is doped with a first dopant of a material having a higher index of refraction than the cladding and with a second dopant of a material that converts optical pump energy in the form of light having a first wavelength into light having a second wavelength different from said first wavelength for amplifying an optical signal beam to be transmitted by the transmission fibre, wherein the second dopant consists of a material that has an energy level wherein its electron population is inverted relative to a lower energy level by the light of the optical pump energy having a first wavelength that is to be supplied, so as to provide an emission of light having a second wavelength different from the first wavelength that is to be stimulated by the optical signal beam for amplifying said optical signal beam; wherein the second dopant has a dopant concentration within the core that increases in radial direction in proportion to a distance to the centre of the core; wherein the core is doped with a third dopant, and wherein the third dopant and a variation in dopant concentration of the third dopant within the core have been selected such that a variation in the refractive index caused by the second dopant is compensated; and wherein average dopant concentrations of the first, the second and the third dopant have been selected so that amplification at a peak of an amplification curve ranges between 0.001 and 0.01 dB/km and wherein attenuation is less than 0.25 dB/km at a wavelength of 1550 nm when no optical pump energy is used.