Weakly coupled few-mode optical fiber with slope type refractive index distribution

Abstract

The invention discloses a weak coupling few-mode optical fiber with slope type refractive index distribution, and belongs to the technical field of optical fiber communication. The weak coupling few-mode optical fiber with the slope type refractive index distribution comprises a cladding and a fiber core arranged in the cladding, the refractive index of the fiber core is larger than that of the cladding, the refractive index of the fiber core is in slope type refractive index distribution on the cross section of the optical fiber, and the refractive index of the fiber core is in symmetrical slope type distribution on the two sides of the optical fiber relative to the horizontal diameter of the optical fiber. Coupling between different order modes and even between degenerate modes is reduced by changing distribution of refractive indexes of fiber core materials, inter-mode crosstalk is reduced, and therefore information transmission capacity of the few-mode optical fiber is effectivelyexpanded. Compared with the optical fiber with a non-circular symmetrical fiber core structure, the optical fiber can be well butted with the conventional circular core optical fiber. In combination with the current multi-core optical fiber, the number of available channels of the optical fiber can be multiplied.

Description

technical field [0001] The invention belongs to the technical field of optical fiber communication, and relates to a weak coupling few-mode optical fiber with slope-type refractive index distribution. Background technique [0002] In recent years, with the rapid development of technologies such as mobile Internet, cloud computing, and big data, the global demand for network capacity is growing rapidly. As a new resource for information bearing, the spatial dimension can partially solve the problem of network capacity supply and demand. The multiplexing of space dimension is referred to as space division multiplexing, and the mode division multiplexing technology in the space division multiplexing technology is considered to be an effective way to expand the capacity of the current single-mode optical fiber communication system. The two main implementation schemes are strong Coupling and weak coupling. The few-mode fibers used internationally in the early days are basically ...

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Problems solved by technology

[0006] 1. Increase the effective refractive index difference: This is the simplest and easiest way. Increasing the effective refractive index of the core can significantly increase the effective refractive index difference of adjacent modes, but it has no obvious effect on degenerate modes, and High doping also poses considerable challenges to the preparation process, and will also cause an increase in transmission loss;

[0007] 2. Ring-assisted structure: Adding a high-refractive index or low-refractive index ring in a specific area of ​​the fiber core can achieve the purpose of adjusting the effective refractive index of the mode, thereby reducing the coupling between different order modes, but the effect on the degenerate mode is not good. obvious;

[0008] 3. Ring core structure: The fiber core is designed as a ring structure, which changes the order and number of supported modes. Although it effectively increases the effective refractive index difference between adjacent modes, it also sacrifices the supported modes to a certain extent. quantity;

[0009] 4. Non-circular symmetric structure: use elliptical or triangular core to break the degeneracy between modes, and also increase LP 21 with LP 02 Strong coupling between modes, but due to the special shape of the core, a large coupling loss will occur when it is connected with a conventional circular core fiber

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