Groove-assisted double-step ring core optical fiber

The invention discloses a groove-assisted double-step ring core optical fiber. The groove-assisted double-step ring core optical fiber comprises a ring core and an outer cladding; the ring core sequentially comprises a central cladding, a second-layer step ring, a first-layer step ring and an annular groove from inside to outside; refractive indexes of the first-layer step ring core and the second-layer step ring core are distributed in a double-step ring core shape; the first-layer step ring core is used for controlling optical fiber normalization frequency so as to regulate and control the number of modes; the second-layer step ring core is used for increasing the effective area of the modes so as to reduce the nonlinear coefficient of each mode of the optical fiber and suppress a radialhigh-order mode; and the double-layer step structure is used for mode regulation and control with higher degree of freedom. The optical fiber can support eight-order OAM modules, the effective refractive index difference bet