摘要：A novel evaluation term and a more reasonable criterion,which is described by a new parameter of brightness factor for active large mode area fiber design,are *** brightness factor evaluation method is based on the transverse mode competition mechanism in fiber lasers and *** brightness factor can be seen as a description of fiber general property since it can represent the output laser brightness of the fiber laser system and because of its ability to resist the nonlinear effect.A core-doped active large pitch fiber with a core diameter of 190 μm and a mode-field diameter of180 μm is designed by this method,and the designed fiber allows effective single-mode operation.