Abstract
A heterodyne interference system developed for space positioning is used to measure a long distance up to 152.85 m. The laser source is a stabilized optical-frequency comb with the repetition frequency of 100 MHz. An acoustic optical modulator generates a shifted frequency of 100.1 MHz so the frequency of heterodyne signal is 100 kHz. The temporal coherence interference happens at discrete positions, where two optical comb pulse trains in the different arms overlap with each other. A piezo-electric transducer scans to find the peak of interference fringe envelope corresponding to the position. The absolute positioning measurement can be realized by shifting the repetition frequency of the optical comb. The experiment results show the reproducibility is no more than 1.5 μm for the distances up to 152.85 m.
