Comparison of ranging precision of dual-comb with different phase-locking methods

This research investigates the time-of-flight (TOF) ranging precision of a dual-comb system, utilizing three distinct phase-locking methods. We continuously collected ranging values over a period of approximately 20 min, then compared the ranging precision across averaging times spanning from 1 µm to 262 s, during which the Allan deviation floor of the TOF ranging is also determined. The results highlight that the dual-comb with two frequency modes locked to two cavity-stabilized continuous-wave (CW) lasers sustains superior ranging precision, achieving an Allan deviation floor of 35 nm at an averaging time of 8 s. Locking the repetition frequencies to a hydrogen maser results in lower precision in comparison to the free-running method for averaging times under 16 µm, and thereafter matches to the free-running precision up to an averaging time of 8 s. These findings are further analyzed through the relative phase noise of the dual-comb’s repetition frequencies.