FEW-MODE OPTICAL FIBRE WITH LOW DEGENERACY

摘要

A few-mode optical fibre with low degeneracy, comprising a fibre core and cladding (3), wherein the fibre core is composed of a main fibre core (1) and 2N auxiliary fibre cores (2), the main fibre core (1) being located in the centre of an optical fibre, the 2N auxiliary fibre cores (2) being symmetrically arranged on the two sides of the main fibre core (1), and the centre of the main fibre core (1) and the centre of the 2N auxiliary fibre cores (2) being located on the same straight line; the main fibre core (1) has the same refractive index as that of the auxiliary fibre cores (2), and the boundary of the main fibre core (1) is tangent to the boundary of the adjacent auxiliary fibre cores (2), the boundaries of the two adjacent auxiliary fibre cores (2) being tangent; and all the diameters of the auxiliary fibre cores (2) are less than the diameter of the main fibre core (1), and the diameters of the auxiliary fibre cores (2) decrease gradually from inside to outside. Destroying the circular symmetry of a refractive index distribution of the optical fibre by introducing the auxiliary fibre cores (2) so as to form a refractive index distribution with double symmetry. This kind of refractive index distribution demotes a four-fold degenerate high-order mode to a two-fold degenerate mode, thereby increasing an effective refractive index difference therebetween, and enabling a mode field distribution form of the high-order mode to be fixed.