Deflection Measurement Using Fiber Optical Gyro (FOG) Wang Lixin Hu Wenbin Prof., State Key Industrial Test Base for Fiber Optic Sensing Technology, WUT, Wuhan 430070, China.The approach of how to measure the track using Fiber Optical Gyro (FOG) is introduced. The advantage of this track measuring method using FOG is proved by the experiment results, and the relationship of the linear velocity and the precision is presented. At the end of the paper, several rules to reduce the error are summarized.fiber optical gyro(FOG); track measurement; deflection measurement