Preform fabrication by soot processes such as outside vapor deposition (OVD) and vapor axial deposition (VAD) commences with deposition of the core followed by cladding deposition, either with the same torch in the former case or multiple torches in the latter. It is well recognized that low-loss single-mode fibers require a clad/core ratio of at least six. An attractive preform fabrication technique would involve overcladding a core rod with soot, gel, or other cost-effective techniques. For such a process lightguide losses are reduced if the core rod includes a thin cladding layer. Furthermore, for dispersion shifted fiber at 1550 mm with low microbending Induced losses, it is desirable for the core to have a graded refractive-index profile.
© 1987 Optical Society of AmericaPDF Article