Abstract: An optical fiber is disclosed that can be used as an active medium in fiber lasers and/or fiber amplifiers, featuring a preferably rare-earth-doped silica active core surrounded by a pure or doped silica cladding layer (“pump core”). The pump core is surrounded by a doped or pure silica inner cladding for guiding pumping radiation within the pump core. Thus, the refractive index of the inner cladding is lower than that of the pump core. The fiber is surrounded by a protective coating made of polymeric material. One or more additional outer cladding layers, having refractive indexes lower than said inner cladding, may optionally be placed between the inner cladding and the protective coating to further protect the polymer coating from damage. Unlike the prior art, the protective coating does not serve as the only cladding, but is assisted by the inner cladding and optional outer cladding(s).

Abstract: An optical fiber is disclosed that can be used as an active medium in fiber lasers and/or fiber amplifiers, featuring a preferably rare-earth-doped silica active core surrounded by a pure or doped silica cladding layer (“pump core”). The pump core is surrounded by a doped or pure silica inner cladding for guiding pumping radiation within the pump core. Thus, the refractive index of the inner cladding is lower than that of the pump core. The fiber is surrounded by a protective coating made of polymeric material. One or more additional outer cladding layers, having refractive indexes lower than said inner cladding, may optionally be placed between the inner cladding and the protective coating to further protect the polymer coating from damage. Unlike the prior art, the protective coating does not serve as the only cladding, but is assisted by the inner cladding and optional outer cladding(s).

Abstract: A double-core light-conducting fiber comprise a pump core, a laser core which is arranged centrically in the pump core, and a cladding surrounding the pump core. The pump core which is constructed with a substantially circular cross section has at least one ground portion on the outside which extends in the light direction of the double-core light-conducting fiber and amounts to 1% to 49% of the diameter of the pump core. A process for the production of the double-core light-conducting fiber and to a double-core fiber laser and to a double-core fiber amplifier are also disclosed which use the double-core light-conducting fiber according to the invention. The substantially round pump core with its centrically arranged laser core enables a simple connection with other fiber-optic components and a simple coupling in of the pumping light.