Patent ID: 7836728

Claim:
A method of manufacturing an optical fiber preform, comprising: inserting two or more core body pieces end-to-end inside a glass cylinder thereby defining joints between adjacent ones of the core body pieces, the core body pieces having a cladding to core diameter ratio (D/d) of four or less, and the cylinder having such inner and outer diameters that finished core rods to be produced have D/d ratios greater than about five; cleaning the core body pieces either before or after the inserting step; mounting the glass cylinder with the inserted core body pieces vertically with respect to a furnace; heating the cylinder and the inserted core body pieces in the furnace thereby elongating the cylinder and the core body pieces inside the cylinder, and collapsing the outside diameter of the cylinder to a determined size to form a core rod; cutting the core rod at one or more positions along the length of the core rod that coincide with the joints between adjacent ones of the core body pieces, thereby yielding a number of core rod sections; depositing a quantity of soot overcladding on the outside circumference of a selected core rod section, and building the outside diameter of the deposited soot overcladding so that the D/d ratio of a finished optical fiber preform is about 15 or more; and consolidating the core rod section with the deposited soot overcladding to obtain the finished optical fiber preform.