The photosensitivity experiment of non - hydrogen - loaded and hydrogen - loaded germanosilicate fiber was done ; the mechanism of non - hydrogen - loaded fiber was compared with that of hydrogen - loaded fiber ; the process of fbg formation was simulated . the results show : the mechanism is color - center model in the non - hydrogen - loaded fiber ; the mechanism is structural model 结果表明：在未载氢的掺锗石英光纤中，起主要作用的光敏机制是色心模型；在载氢掺锗石英光纤中，起主要作用的光敏机制是结构模型。
