Abstract: An optical-fiber displacement interferometer was proposed on the basis of the optical Doppler effects and heterodyne technique. The proposed interferometer was assembled by using the components well developed in the telecommunication industry, which consisting of a fiber-pigtailed semiconductor laser, a three-port optical circulator, a fiber probe, a wideband detector, a high-sampling-rate broadband oscilloscope, and so on. The coaxial configuration for the signal light and reference light is adopted so that the proposed interferometer can measure velocities of any reflecting surface and overcomes the effects of polarization-mode dispersion, and its work distance is up to 20 mm. The velocities of the explosively-driven metal plate were measured by the proposed interferometer and compared with those measured by the velocity interferometer system for any reflector. Measured results show the velocities by these two methods are accordant with each other.