Spatial positioning measurements up to 150 m using temporal coherence of optical frequency comb

A heterodyne interference system using an optical frequency comb has been developed for spatial positioning measurements and applied to long distances up to 152.85 m. The laser source is a Rb-stabilized optical-frequency comb, and temporal coherence interference occurs at discrete spatial positions, where two optical comb pulse trains in the different arms overlap. A piezoelectric transducer scans to find the peak of the interference fringe envelope corresponding to the position. The measurement of the absolute position is accomplished by shifting the frequencies of the optical comb by 100.1 MHz. The experimental results show that the measurement reproducibility is no more than 1.4 μm for distances up to 152.85 m and that the accuracy is 1.1 μm for a distance of 50.951 m.