Abstract In this paper ,we use a fiber mode coup領(lǐng) method to analyse a fiber optical velocity interferometer system for any reflector and use it to measure low velocity impact specimens with diffuse reflecting surface. The experiment results agree with theoritcal analysises fairly and the profile of velocity vs time is first obtained in the experiment . Key words fibre mode coup領(lǐng) method , optical velocity interferometer , low velocity impact , diffuse reflecting surface 全光纖多功能研發(fā)平臺