A multimode optical fiber having a core region. The core region includes silica, has an outer radius r1, and has a maximum relative refractive index of about 1.5% or less. Additionally, the multimode optical fiber is configured to have an effective bandwidth of about 4.7 GHz-Km or greater for an excited portion of the core region that has a diameter greater than 50 microns, the effective bandwidth being at a wavelength that is within a range of between about 800 and about 1370 nm.