Abstract

The physical structures of UV-induced refractive index changes associated with fiber Bragg gratings (FBGs) in Ge-SiO₂ core fibers reported to date are reviewed and discussed. They are (1) induced mechanical property changes: volume changes (densification or dilation) and core-cladding interfacing tension changes, and (2) induced color centers: Ge E’, Ge(1) and Ge(2) paramagnetic defects, and GeH non-paramagnetic defects. Conflicting structural models of the paramagnetic defects proposed in the literature can be resolved by taking into account their different contributions to the refractive index of FBGs.

© 1999 Optical Society of America