Enhanced photosensitivity in tin-codoped germanosilicate optical fibers

Enhanced photosensitivity is found in tin-codoped germanosilicate optical fibers. A photo-induced refractive index change (/spl sim/1.4×10/sup -3/) 3 times larger than that observed in pure germanosilicate fibers has been demonstrated. Unlike the technique of using boron-codoping to enhance the photosensitivity of germanosilicate fibers, tin-doping does not have a significant effect on fiber loss at the important telecommunication window of 1.55 μm. High temperature stability of the gratings in tin-codoped germanosilicate fibers is also much over boron-codoped fibers.