Self-calibrated free-running dual-comb ranging using subsampled repetition frequency information

Dual-comb ranging (DCR) is an emerging absolute distance measurement method with rapid speed, high precision, and wide ambiguity range. DCR has important applications in remote sensing, large-scale manufacturing, and aerospace exploration. However, the typical DCR system requires cumbersome phase-locking electronics for frequency stabilization and distance calibration, which hinders the practical application of DCR. In this paper, we demonstrate a free-running DCR scheme based on two free-running mode-locked fiber lasers. Two fiber lasers are environment-shared to improve the anti-aliasing capability. We then introduce a self-calibration technique that can directly extract the subsampled repetition frequency information from the interferograms (IGMs). By using this technique, real-time calibration of measured distance can be achieved without extra repetition frequency detection module and frequency counter. The system realizes a 5.3 mu m precision for-1 m stand-off distance at-1 kHz acquisition speed. With averaging, the measurement precision drops to-101 nm at the averaging time of 3 s. The ambiguity range of our DCR system is-2.6 m due to the relatively small repetition frequency. For dynamic distance measurement, it shows good consistency with a commercial heterodyne interferometer. Our method provides a cost-effective scheme for high-performance absolute distance measurement, and it is promising for promoting DCR system out of the laboratory and realizing field-deployed applications.