Crystalline optical fiber and its method of manufacture

Abstract From the Canadian patent

A crystalline metal halide optical fiber having a two or a three layer structure. The core consists of relatively small crystals. An inner crust surrounds the core and has the same composition but consists of relatively large crystals. An optical outer crust surrounds the inner crust and has a different composition from the inner crust but has generally the same sized crystals. The differing crystal sizes can be produced from a preform by extruding a crystal at a low uniform temperature at a relatively high speed.