FABRICATION OF SiO2-GeO2 CORE OPTICAL FIBERS BY THE SOL-GEL METHOD.

In order to obtain bubble-free optical fibers of the SiO//2-GeO//2 system by the sol-gel method, the temperature required for collapsing pores in dry gels was increased by adding an ammonia water to the sol starting alkoxide solution. It is also found that the addition of the ammonia water increases the difference in reaction rates for the hydrolysis of Si and Ge alkoxides and causes the precipitation of hexagonal GeO//2 crystals in the gel. The conversion efficiency of Ge alkoxide to GeO//2 in the glass decreased with an increasing amount of precipitating GeO//2 crystals in the gel. Using this sol-gel technique GeO//2-doped silica core optical fibers have been fabricated with a minimum optical loss of 9 db/km at 1. 07 mu m.