Patent ID: 8848285

Claim:
An optical fiber comprising: (i) a glass core doped with greater than 300 ppm of Er 2 O 3 and at least 0.5 wt % of Al 2 O 3 , with a radius R 1 from about 3μm to about 15μm, a maximum relative refractive index delta Δ 1MAX from about between 0.3% to 2% relative to the glass cladding; an effective area of LP01 mode between 10 μm 2 and 100 μm 2 at 1550 nm, the glass core radius R 1 and refractive index are selected such that the core is capable of supporting the propagation and transmission of an optical signal with X number of LP modes at a wavelength of 1550 nm, wherein X is an integer greater than 1 and less than 20; and (ii) a glass cladding surrounding and in direct contact with the glass core, wherein the glass core comprises a maximum relative refractive index Δ 1MAX such that Δ 1MAX >Δ 4MAX .