Origin of Excess Loss in Single-Mode Optical Fibers with High GeO2-Doped Silica Core

The problem of excess loss in single-mode germanosilicate optical fibers with GeO2content 20 to 35 mol% is experimentally studied. Excess loss in such fibers is due to the drawing-induced defects, UV absorption tail and scattering. It is sensitive to drawing conditions and to codoping with F and P. Codoping with P results in additional loss presumably caused by P-related drawing-induced defects. Codoping with F diminishes the excess loss presumably by smoothing the inhomogeneous distribution of GeO2in SiO2–GeO2glass.