Method of making optical fiber preform having one step fluorine trench and over clad

摘要

Forming a low refractive index trench region (112) having a first density; forming an inner barrier layer (116a) containing silica around the trench region at a second density greater than the first density; Depositing a silica-based soot around a barrier layer of 1 to form an overclad region (114) at a third density that is less than a second density; inserting a core cane (102) into the trench-overcladding structure; Forming an outer barrier layer (116b) containing silica in an outer portion of the overcladding region at a fourth density greater than a third density; flowing a downdopant containing gas through the trench-overcladding structure (110) Doping a trench region with a down dopant, wherein the barrier layer (116a, 116b) Diffusion of downdopant to de region (114) within is relaxed,; and, trench-a step of compacting the over-cladding and core caneThe method comprising the steps of: A method of making a consolidated trench-overclad structure having inner and outer barrier layers is also provided.