Photonic lanterns comprising optical fibers having up-down doped claddings

A method comprising:

• directing light into a first end of a photonic lantern, the photonic lantern further comprising:
• three or more optical fibers housed within a glass capillary, each optical fiber comprising a core surrounded by a cladding;
• a second end opposite the first end, wherein the photonic lantern tapers between the first end and the second end such that a diameter of the glass capillary at the first end is greater than a diameter of the glass capillary at the second end;
• the cladding of at least two of the three or more optical fibers comprises an up-down doped cladding doped with a dopant combination comprising an up-dopant and a down-dopant, wherein:
• the up-dopant increases the effective refractive index of the up-down doped cladding;
• the down-dopant decreases the effective refractive index of the up-down doped cladding;
• and
• the dopant combination decreases a material viscosity of the up-down doped cladding;
• and
• the cladding of at least one of the three or more optical fibers comprises a silica cladding, wherein:
• a difference in the effective refractive index between the silica cladding and the up-down doped cladding is greater in a tapered region and at the second end of the photonic lantern than at the first end of the photonic lantern such that the light propagating from the first end to the second end of the photonic lantern retains modal isolation;
• and
• receiving the light output at the second end of the photonic lantern with a first end of a multi-mode optical fiber.

A method of manufacturing a photonic lantern, the method comprising:

• applying heat to a central region of a photonic lantern preform, the photonic lantern preform comprising:
• three or more optical fibers housed within a glass capillary, each optical fiber comprising a core surrounded by a cladding;
• and
• a first preform end opposite a second preform end, wherein:
• 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 decreases the effective refractive index of the up-down doped cladding, the dopant combination comprising an up-dopant that increases the effective refractive index of the up-down doped cladding and a down-dopant that decreases the effective refractive index of the up-down doped cladding;
• and
• the cladding of at least one of the three or more optical fibers comprises a silica cladding;
• stretching the photonic lantern preform in a first direction from the first preform end and in a second direction from the second preform end such that the photonic lantern preform tapers in the central region;
• and
• separating the central region to form at least one photonic lantern from the photonic lantern preform, wherein:
• the photonic lantern comprises a first end corresponding with the first preform end of the photonic lantern preform and a second end corresponding with the central region of the photonic lantern preform;
• the photonic lantern tapers between the first end and the second end such that a diameter of the glass capillary at the first end is greater than a diameter of the glass capillary at the second end;
• and
• a difference in the effective refractive index between the silica cladding and the up-down doped cladding is greater in a tapered region and at the second end of the photonic lantern than at the first end of the photonic lantern.