| 摘要 |
PROBLEM TO BE SOLVED: To provide a few-mode rare-earth-doped amplifier fiber having an equalized gain for a supported signal transmission mode.SOLUTION: A fiber according to the present invention has a high-refractive-index core surrounded by a cladding region having a lower refractive index. The core has a radius aand a refractive index difference &Dgr;nrelative to the surrounding cladding region, and is configured to support, at a selected signal wavelength, a set of lower-order fiber modes having an optical field with a diameter greater than 2*a. The fiber further includes an active region which has an inner portion coextensive with the core and an outer portion surrounding the inner portion and extending into a cladding, and is doped with a rare-earth dopant. The active region has an outer radius agreater than aand encompasses the optical field of the set of lower-order fiber modes at the selected signal wavelength. |
