Photosensitive indium-doped germano-silica fiber for strong FBGs with high temperature sustainability

A highly photosensitive indium-doped germano-silicate fiber (In-Ge fiber) has been developed for fiber Bragg grating (FBG) fabrication. Tests carried out on the photosensitivity of the fiber have shown that the grating written into this fiber may show a high refractive index modulation, of 3.2×10^-4. Annealing experiments of the FBGs written into this fiber have shown that the FBGs can survive a temperature as high as 900°C for 24 h and even 1000°C for over 2 h. The results of the high temperature annealing studies are presented, as well as the relationship between the peak wavelength of the FBG and temperature, indicating the value of FBG-based devices for high temperature use in such fibers.