Spun round core fiber
View Patent ↗Optical waveguide cores having refractive index profiles that vary angularly about a propagation axis of the core can provide single-mode operation with larger core diameters than conventional waveguides. An optical waveguide includes a core that extends along a propagation axis and has a refractive index profile that varies angularly about the propagation axis. The optical waveguide also includes a cladding disposed about the core and extending along the propagation axis. The refractive index profile of the core varies angularly along a length of the propagation axis.
1. A method of making a core rod preform, comprising:
situating one or more silica rods having a first index of refraction in a silica tube;
situating one or more silica rods having a second index of refraction in the silica tube;
collapsing the silica tube to form a core rod preform; wherein
the core rod preform has a refractive index profile that varies angularly about a longitudinal axis of the preform.
2. A method, comprising:
situating a core rod within a cladding tube to obtain an optical fiber preform, the core rod having a refractive index profile that varies angularly about a longitudinal axis of the core rod; and
drawing the optical fiber preform to create an optical fiber; wherein
the optical fiber preform is rotated while being drawn such that the refractive index profile of a core of the resultant optical fiber varies angularly along the longitudinal axis of the core.
3. The method of claim 2 , wherein the angular variation of the refractive index profile of the core is periodic along the longitudinal axis of the core.
4. The method of claim 2 , wherein the angular variation of the refractive index profile of the core is aperiodic along the longitudinal axis of the core.
5. An optical waveguide, comprising:
a core that extends along a propagation axis, the core having a refractive index profile that varies angularly about the propagation axis; and
a cladding disposed about the core and extending along the propagation axis, the cladding having a refractive index profile that varies angularly about the propagation axis;
wherein the refractive index profile of the cladding and the refractive index profile of the core vary angularly along the propagation axis;
wherein the cladding further comprises one or more mode-discriminating regions, and the one or more mode-discriminating regions are situated a radial distance from the core, the radial distance corresponding to a wavelength of optical radiation to be propagated through the optical waveguide.
6. The optical waveguide of claim 5 , wherein:
the core has a round cross-section; and
the cladding has a polygonal cross-section.