Abstract: According to embodiments, an optical fiber may include a core portion comprising a radius rC, a centerline CL, a numerical aperture NA greater than or equal to 0.15 and less than or equal to 0.25, a graded relative refractive index profile having a maximum relative refractive index ?Cmax and an ? value greater than or equal to 1 and less than or equal to 3. The core portion may include an up-dopant with a graded concentration from the radius rC to the centerline CL and an attenuation dopant with a constant concentration from the centerline CL of the core portion to the radius rC of the core portion. The optical fiber is multi-moded for wavelengths of light within a range from 800 nm to 1350 nm and an attenuation of the optical fiber wavelengths between 800 nm and 1000 nm is greater than or equal to 0.5 dB/m.

Abstract: According to embodiments, an optical fiber may include a core portion comprising a radius rC, a centerline CL, a numerical aperture NA greater than or equal to 0.15 and less than or equal to 0.25, a graded relative refractive index profile having a maximum relative refractive index ?Cmax and an ? value greater than or equal to 1 and less than or equal to 3. The core portion may include an up-dopant with a graded concentration from the radius rC to the centerline CL and an attenuation dopant with a constant concentration from the centerline CL of the core portion to the radius rC of the core portion. The optical fiber is multi-moded for wavelengths of light within a range from 800 nm to 1350 nm and an attenuation of the optical fiber wavelengths between 800 nm and 1000 nm is greater than or equal to 0.5 dB/m.

Abstract: A multimode optical fiber, and a method of making the fiber, are provided according to the following steps and elements: forming a core preform with a graded refractive index that includes silica and an up-dopant; drawing the core preform into a core cane; forming an inner annular segment preform that includes silica soot and an up-dopant surrounding the core cane; and forming a depressed-index annular segment preform that includes silica soot surrounding the inner annular segment preform. The method also includes the steps: forming an outer annular segment preform that includes silica soot and an up-dopant surrounding the depressed-index annular segment preform; doping the inner, depressed-index and outer annular segment preforms simultaneously or nearly simultaneously with a down-dopant; and consolidating the segment preforms simultaneously or nearly simultaneously into inner, depressed-index and outer annular segments.

Abstract: A multimode optical fiber, and a method of making the fiber, are provided according to the following steps and elements: forming a core preform with a graded refractive index that includes silica and an up-dopant; drawing the core preform into a core cane; forming an inner annular segment preform that includes silica soot and an up-dopant surrounding the core cane; and forming a depressed-index annular segment preform that includes silica soot surrounding the inner annular segment preform. The method also includes the steps: forming an outer annular segment preform that includes silica soot and an up-dopant surrounding the depressed-index annular segment preform; doping the inner, depressed-index and outer annular segment preforms simultaneously or nearly simultaneously with a down-dopant; and consolidating the segment preforms simultaneously or nearly simultaneously into inner, depressed-index and outer annular segments.

Abstract: Methods for forming optical fiber preforms are disclosed. According to one embodiment, a method for forming an optical fiber preform includes forming a preform core portion from silica-based glass soot. The silica-based glass soot may include at least one dopant species for altering an index of refraction of the preform core portion. A selective diffusion layer of silica-based glass soot may be formed around the preform core portion to form a soot preform. The selective diffusion layer may have an as-formed density greater than the density of the preform core portion. A diffusing species may be diffused through the selective diffusion layer into the preform core portion. The soot preform may be sintered such that the selective diffusion layer has a barrier density which is greater than the as-formed density and the selective diffusion layer prevents diffusion of the at least one dopant species through the selective diffusion layer.