A photonic lantern includes three or more optical fibers housed within a glass capillary, each optical fiber includes a core and a cladding. The photonic lantern tapers between a first and second end such that a diameter of the glass capillary is greater at the first end than the second end and the cladding of at least two of the three or more optical fibers comprises an up-down doped cladding doped with a dopant combination that includes an up-dopant and a down-dopant. The up-dopant increases and the down-dopant decreases the effective refractive index of the up-down doped cladding. The dopant combination decreases a material viscosity of the up-down doped cladding such that a difference in the effective refractive index between a silica cladding and the up-down doped cladding is greater in a tapered region and at the second end than at the first end.

Disclosed herein is a fiber pump combiner, comprising, a multi-clad fiber comprising an outer cladding layer and an inner cladding layer, a plurality of tapered trenches formed in the inner cladding layer and a plurality of pump fibers, wherein the plurality of pump fibers are tapered and fused into corresponding ones of the plurality of tapered trenches.

An optical fiber comprising: (i) a core region comprising an outer radius r.sub.1, and 3.0r.sub.17.0 microns and a relative refractive index .sub.1max and 0.32%.sub.1max0.5%; (b) a depressed index cladding region surrounding the core region comprising an outer radius r.sub.3 and a relative refractive index .sub.3 less than 0.2%, and trench volume V.sub.3 wherein 45% -micron.sup.2|V.sub.3|200% -micron.sup.2; (c) a first outer cladding region surrounding the depressed index cladding region and comprising a relative refractive index .sub.4 and an outer radius r.sub.4; and (d) a second outer cladding layer comprising 5 wt %-20 wt % titania, a relative refractive index .sub.5, and a thickness T.sub.M, wherein 3 micronT.sub.M30 microns, and outer radius r.sub.565 microns; the optical fiber has a mode field diameter MFD.sub.1550 and 8 micronsMFD.sub.155010.5 microns, a cutoff wavelength 1550 nm when bent 1 turn around a 2.5 mm radius mandrel, and a bending loss at 1550 nm when using a mandrel comprising a radius of 2.5 mm of 1.0 dB/turn.

Disclosed herein is a fiber pump combiner, comprising, a multi-clad fiber comprising an outer cladding layer and an inner cladding layer, a plurality of tapered trenches formed in the inner cladding layer and a plurality of pump fibers, wherein the plurality of pump fibers are tapered and fused into corresponding ones of the plurality of tapered trenches.

An optical fiber comprising: (i) a core region comprising an outer radius r.sub.1, and 3.0r.sub.17.0 microns and a relative refractive index .sub.1max and 0.32%.sub.1max0.5%; (b) a depressed index cladding region surrounding the core region comprising an outer radius r.sub.3 and a relative refractive index .sub.3 less than 0.2%, and trench volume V.sub.3 wherein 45% -micron.sup.2|V.sub.3|200% -micron.sup.2; (c) a first outer cladding region surrounding the depressed index cladding region and comprising a relative refractive index .sub.4 and an outer radius r.sub.4; and (d) a second outer cladding layer comprising 5 wt %-20 wt % titania, a relative refractive index .sub.5, and a thickness T.sub.M, wherein 3 micronT.sub.M30 microns, and outer radius r.sub.565 microns; the optical fiber has a mode field diameter MFD.sub.1550 and 8 micronsMFD.sub.155010.5 microns, a cutoff wavelength <1550 nm when bent 1 turn around a 2.5 mm radius mandrel, and a bending loss at 1550 nm when using a mandrel comprising a radius of 2.5 mm of 10 dB/turn.

An apparatus for combining optical radiation, wherein the apparatus comprises a bundle of input optical fibers formed of glass, a taper, and an output optical fiber, wherein the taper is fused to the output optical fiber; and the apparatus comprises at least one cladding mode stripper to strip out higher order modes that would otherwise degrade a polymer coating on at least one of the input optical fibers and the output optical fiber.

A system for positioning an optical preform in a furnace is provided that includes an upper muffle and a downfeed handle assembly with a tube defining a first end and a second end, the second end extending into the upper muffle. A handle is disposed within the tube. A second end of the handle extends into the upper muffle and a seal assembly is positioned around both the tube and the handle. The first end of the handle extends through the seal assembly and a drive assembly is coupled with the downfeed handle.

Disclosed herein is a fiber pump combiner, comprising, a multi-clad fiber comprising an outer cladding layer and an inner cladding layer, a plurality of tapered trenches formed in the inner cladding layer and a plurality of pump fibers, wherein the plurality of pump fibers are tapered and fused into corresponding ones of the plurality of tapered trenches.

There is described an optical fiber coupler in which at least one fiber is a multiple-clad fiber, containing a single-mode core supporting a single guiding mode and an inner multi-mode cladding guiding multiple modes. The multiple-clad fiber is fused with a second fiber of a different etendue to create an optical fiber coupler having an enhanced multi-mode signal transmission.

Disclosed herein is a fiber pump combiner, comprising, a multi-clad fiber comprising an outer cladding layer and an inner cladding layer, a plurality of tapered trenches formed in the inner cladding layer and a plurality of pump fibers, wherein the plurality of pump fibers are tapered and fused into corresponding ones of the plurality of tapered trenches.