Large-mold-field gain fiber used for outputting single-mode lasers

The invention discloses a large-mold-field gain fiber used for outputting single-mode lasers. The large-mold-field gain fiber comprises a fiber core (1), a trench layer (2), a first wrapping layer (3) and a second wrapping layer (4), wherein the fiber core (1) is wrapped with the trench layer (2), the first wrapping layer (3) and the second wrapping layer (4) in sequence. The refractive index of the second wrapping layer (4) is lower than that of the fiber core (1), and the refractive index of the trench layer (2) is lower than that of the second wrapping layer (4). The large-mold-field gain fiber has the advantages of being high in high-order mode inhibiting capability, large in basic mode overlap factor and the like; moreover, the refractive index of the fiber is distributed in an axisymmetric mode, and the fiber has the advantages that the fiber processing technology is mature, and the processing difficulty is low.