ALKALI-DOPED OPTICAL FIBER, ITS PREFORM AND METHOD OF MAKING THE SAME

摘要

Disclosed is an alkali-doped optical fiber preform and method for making the same. A silica glass member, such as a rod or the like is heated in a furnace chamber at a temperature of less than 75 C below the softening point of the glass rod in an environment containing an alkali metal vapor to form an alkali metal oxide doped glass rod. This method provides a peak concentration in the outer half portion of the silica glass member. The alkali metal oxide doped glass member may be overclad with additional glass to form an optical fiber preform ready for drawing into an optical fiber. Alternatively, the alkali metal oxide doped glass member may be inserted into a porous, glass soot optical fiber preform or inserted into a tube comprising solid glass.