Method to Change Localized Pump Absorption Efficiency and Localized Heating in Doped Optical Fiber by Cross Sectional Processing During Fiber Draw

Herein is provided a fiber length including a doped fiber core extending over the fiber length. First and second cladding regions radially surround the core. At least one pump light input site is arranged to accept input pump light into the first cladding region. A low-absorption length over which the first cladding region has a first cross-sectional geometry produces a first level of absorption of input pump light from the first cladding region to the core, extending from a pump light input site for an extent over which the doped core can absorb at least about 10% of input pump light from the first cladding region. A high-absorption section over which the first cladding region has a second cross-sectional geometry produces a second level of absorption of input pump light from the first cladding region to the core, greater than the first level of absorption of input pump light.