The dark current and noise density of the PIN photo-electric detector are deteriotating immensely under the space irradiation environment and the corresponding characteristics of the fiber optic gyroscopes(FOGs) have the same tendency.To monitor the working status of the PIN detector,a method is introduced to realize the on-orbit supervision of the noise density from the PIN detector.When FOGs start up,light source′s current is switched off and there is no light arriving at the PIN detector,so t...