Measurement of linear velocity using a resonant ring interferometer with alow-coherence light source

It is demonstrated theoretically and experimentally that linear velocities of reflecting objects may be measured using a resonant ring interferometer with a low-frequency light source. The limiting sensitivity of this interfe rometer is estimated. It is shown that a resonant ring interferometer can b e used to measure extremely low linear velocities corresponding to subhertz Doppler frequency shifts of light, which cannot be measured by conventiona l Doppler techniques based on direct measurements of the frequency differen ce between the initial and reflected waves. (C) 1999 American Institute of Physics. [S1063-7850(99)00612-6].