| 摘要 |
The instant invention concerns optical fibers that have complex-valued Vc-parameters due to gain g established by active dopants that are doped into the fiber core in accordance with a doping profile. In particular, the doping levels are very high, such that the gain g makes a sufficiently large contribution to an imaginary part of the complex-valued Vc-parameter to define at least one gain-guided mode, e.g., the fundamental mode or several low-order modes of radiation in the optical fiber. The fiber does not require any index-guiding effects to a single mode or just a few of the lowest-order modes in large cross-section cores having diameters in the range from 50 mum to 500 mum in diameter and yield kilowatt level output power. The fiber may, in addition to gain-guiding, take advantage of a refractive index profile to provide for index-guiding or index-antiguiding effects in addition to gain-guiding.
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