Dual-comb parallel sampling absolute distance measurements with an extended non-ambiguity range

Abstract Precise absolute distance measurements are crucial in both scientific and industrial fields. Among various techniques, dual-comb ranging stands out due to its high precision and fast acquisition rate. However, the inherent periodicity of the comb pulse train leads to the limited non-ambiguity range (NAR) and periodic measurement dead zones, thereby impeding its practical applications. Here, we propose and demonstrate an arbitrary absolute distance measurement system utilizing dual repetition rate parallel linear asynchronous optical sampling. Based on the broad spectrum of optical frequency combs and wavelength division multiplexing technology, two sets of pulse trains with different wavelength ranges and repetition rates are used as signal pulses for simultaneous distance measurement. This approach straightforwardly extends the NAR to tens of kilometers by leveraging the Vernier effect. Additionally, incorporating a variable optical delay line in the reference path eliminates the measurement dead zones, thus enabling continuous measurements. Experimental results demonstrate that our proposed ranging system exhibits an Allan deviation of approximately 0.32 μm at an averaging time of 440 ms. Compared to commercial interferometers, the ranging accuracy is better than 3.8 μm for a target mirror positioned about 7 m away. Overall, the proposed system provides a compact, fast, high-precision, and dead-zone-free long-distance ranging solution with significant practical value for various precision engineering applications.