The invention relates to a low-
crosstalk large-mode-area multi-core
fiber and a preparation method thereof. The low-
crosstalk large-mode-area multi-core
fiber is characterized by comprising a centralcore, a
coating layer I surrounding the central core, a plurality of bypass cores and a
coating layer II, wherein the plurality of bypass cores extend along an
optical fiber axis and are arranged in aregular polygon manner; and the
coating layer II covers the central core, the coating layer I and the plurality of bypass cores. Different elements are doped into a process for manufacturing the central core, the bypass cores, the coating layer I and the coating layer II, so that refractive indexes of the four parts generate a certain
refractive index difference, and the refractive indexes of thefour parts are ranked from the central core to the bypass cores to the coating layer I to the coating layer II from high to low. The purpose of the design is to effectively suppress inter-core
crosstalk of the central core and the bypass cores. Meanwhile, by utilizing a principle that the
refractive index of the coating layer I is lower than that of the central core or the bypass cores, energy inthe central core is further prevented from leaking out, the coating layer II has the lowest
refractive index and located on the outermost side of the multi-core
fiber, leakage of energy of the bypasscores is suppressed, the stability of the
optical fiber structure is ensured, and the transmission efficiency of light signals is increased.