Multimode fiber optic with high bandwidth in an extended wavelength range, and the corresponding multimode optical system

摘要

Multimode optical fiber, comprising: a central core surrounded by an external optical coating, said central core having (i) an outer radius a, (ii) a transition radius Rt = a.rt which is smaller than the outer radius a , (iii) a maximum refractive index n0, (iv) a minimum refractive index nCl, and (v) a gradual index profile n (r) that is a function of the radial distance r from the center of said central core , wherein said central core is co-doped with at least fluorine F and Germanium GeO2, wherein said gradual index profile n (r) of the central core is defined by the following equation: ** (See formula) ** where: ** (See formula) ** where the parameter alpha α (r) is a function of the radial distance r from the center of said central core, said parameter alpha α (r) having two or more different values than along radial positions from the center of said central core to the external central core radius a; wherein the weight ratio of fluorine F in the center of the core ([F] r = 0) is between 0 and 3% by weight and the weight ratio of fluorine F in the outer radius of the core ([F] r = a) is between 0.5% by weight and 5.5% by weight, with [F] r = a - [F] r = 0 0.4% in weight; characterized in that the molar fraction of GeO2 in the outer radius of the nucleus ([Ge] r = a) is between 1.5 mol% and 17.5 mol%.