Abstract: Described herein is a method for making a depressed index cladding for the inner cladding of an optical fiber. The method involves making the depressed index cladding in two steps. The innermost portion of the inner cladding is produced using a soot method, thereby deriving the advantages of the soot method for the region of the cladding that carries the most optical power, then forming the remaining portion of the inner cladding layer using a rod-in-tube step. This method effectively marries the advantages and disadvantages of both methods.

Abstract: The specification describes an improved VAD method wherein a multi-layer preform, with three or more layers of material having different refractive indices, are produced. The method involves the combination of tandem dual torch deposition, and multiple pass deposition, without consolidation between multiple passes.