IMPROVED ACTIVE OPTICAL FIBERS WITH WAVELENGTH-SELECTIVE FILTERING MECHANISM, METHOD OF PRODUCTION AND THEIR USE

摘要

The invention relates to optical fibers for use in optical amplification of light, such as in optical fiber amplifiers and lasers and for use in delivery of high power light, in particular to a scheme for reducing amplified spontaneous emission at undesired wavelengths. The invention further relates to articles, methods and use. An object of the invention is achieved by a micro- structured optical fiber, which is adapted to guide light by the photonic bandgap effect and to have one or more pass bands and at least one stop- band over a wavelength range from ^?stop1 to ^?stop2- In an aspect of the invention, the at least one stop-band provides filter functions that suppress nonlinear effects. In another aspect, the core region is actively doped, and the active material has an emission spectrum with a higher value of the emission cross section s_E at a wavelength ^?ASE between ^?stop1 and ^?stop2 than outside said wavelength range such that amplified spontaneous emission and lasing within the wavelength range from ^?stop1 to ^?stop2 is reduced. In still another aspect, the optical fiber exhibits photonic bandgaps at different wavelength ranges in different radial directions of a cross section of the optical fiber.