WIDEBAND MULTIMODE CO-DOPED OPTICAL FIBER EMPLOYING GeO2 AND Al2O3 DOPANTS

A method of forming a wideband multimode co-doped optical fiber, comprising:

• a) forming a preform, the preform comprising:
• i) a preform co-doped core having a preform core outer edge and comprising silica and co-doped with a first radially varying concentration of GeO2 that decreases with the radial coordinate r out to the preform core outer edge and a second radially varying concentration of Al2O3 that increases with the radial coordinate r out to the preform core outer edge;
• ii) a preform cladding immediately surrounding the preform co-doped core and comprising silica, the preform cladding having an inner preform cladding region of relative refractive index Δ2, an intermediate preform cladding region having a relative refractive index Δ3 with a minimum value Δ3MIN, and an outer preform cladding region having a relative refractive index Δ4, wherein the intermediate cladding region comprises a moat and wherein Δ3MIN<Δ2, Δ4;
• and
• b) drawing the preform to form the wideband multimode co-doped optical fiber comprising a co-doped fiber core defined by the preform co-doped core and having a fiber core outer edge and a diameter in a range from 20 microns to 70 microns and having the first and second radially varying concentrations of GeO2 and Al2O3 out to the fiber core outer edge, and a fiber cladding surrounding the co-doped fiber core and defined by the preform cladding and having a fiber inner cladding region having the relative refractive index Δ2, a fiber intermediate cladding region having the relative refractive index Δ3 with the minimum value Δ3MIN, and a fiber outer cladding region having the relative refractive index Δ4, wherein the fiber intermediate cladding region comprises a moat and wherein Δ3MIN<Δ2, Δ4;
• and
• c) wherein the wideband multimode co-doped optical fiber has a wavelength band Δλ of at least 100 nm having a peak wavelength λP in a wavelength range from 800 nm to 1200 nm and a bandwidth BW≤5 GHz·km.