Enhanced photosensitivity is found in Tin-codoped germanosilicate optical fibers. A photo-induced refractive index change (similar to 1.4 x 10(-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 mu m. High temperature stability of the gratings in Tin-codoped germanosilicate fibers is also much over Boron-codoped fibers.