Specialty Optical Fibers Handbook

rod-in-tube process are formed by dispersion, milling, casting, and gelation of

colloidal silica. After removal from the mold and air-drying, they are placed over

a core rod and the assembly is dehydrated, consolidated, and drawn into fiber. A

satisfactory interface, free of bubbles and other defects, must be obtained be-

tween the core rod and the gel-derived overcladding tube. By proper cleaning of

the core rod and appropriate consolidation conditions, the loss of the eventual

fiber can be as low as that of the original core rod.

On the right side of the graph, instead of casting a tube, the wet gel is

granulated into particles, which are fed through ...