This report is a part on going research to develop high temperature optical sensors. We report our design and analyze of a hydrogen loaded fiber Bragg grating (FBG) temperature sensor range from room temperature to over 1000?C. FBGs were fabricated in hydrogen loaded Ge-doped fibers using 248 nm excimer laser and their performance characteristics were tested. The gratings have shown stabilized at temperatures in excess of 700?C and survived at temperatures in excess of 930?C. These testing reveal the thermal reliability of tested gratings is related to the refractive index modulation inside the core of FBGs. In this research, we also found the high temperature resistance FBG could be formatted using conventional hydrogen loaded FBG, and stabilized in excess of 1000?C. Our experimental results provide a better understanding of the formation to the hydrogen loaded FBGs and their decay behavior at elevated temperatures.