Photorefractivity in Ge0 sub 2 -Doped Silica Fibers.

Photorefractivity has been observed in several Ge0 sub 2 -doped fibers. The effect is mainfested by formation of a grating in the fiber core introduced by laser radition in the green part of the spectrum. The grating is a distributed Bragg reflector which selectively reflects light at the writing wavelength. Reflections of up to 50% in a 15 cm length of fiber have been observed. The grating persists for at least 5 days after being written.