Method and apparatus for producing crystalline cladding and crystalline core optical fibers

A method for preparing a crystalline clad and crystalline core optical fiber, comprising:

• securing a crystalline fiber core having a refractive index and a first end and a second end in a holder with no or minimized thermally induced stress, wherein the first end of the crystalline fiber core is secured in the holder and wherein the second end is free to move in at least an axial direction of the fiber within the holder;
• immersing the crystalline fiber core into at least one molten liquid phase epitaxy (LPE) solution comprising at least one flux and at least one cladding until a crystalline cladding layer has formed thereon, said crystalline cladding layer having a lower refractive index than the crystalline fiber core refractive index;
• further comprising adding the molten LPE solution through a 1-dimensional or 2-dimensional mesh type bottom support, wherein the molten flux passes through the mesh type bottom support and there is a relative movement between the fiber core preform and mesh bottom support along at least the axial direction of the fiber during an LPE growing process, resulting in a uniform cladding growth, wherein the crystalline fiber core and mesh type bottom support is separated while the molten flux is still at a molten liquid state by creating a relative translation along an axial direction of the crystalline fiber core, after the crystalline fiber core and mesh bottom support are pulled out of the crucible.