Optical fibers for high power lasers and amplifiers

High power fibers are commonly designed with a double-cladding structure, where an outer low-index region acts as a cladding for a multi-mode pump core. In the center of the pump core is placed a single-mode signal core, doped with active material such as ytterbium. The major advantage of the double-clad design, over the more traditional core pumped variety is the large pump area and high numerical aperture, enabling pumping with relatively low-cost, high-power, multimode diode stacks