Enhanced Dual-Comb Underwater Ranging via an Improved VMD Algorithm

Advanced sensors and signal processing algorithms are significant for the use of remotely-operated vehicles and autonomous underwater vehicles. The distance/length measurement is the basis of many sensing functions, including positioning, tracking, surface reconstruction, and pose determination. Optical-based ranging sensors have been proven as a promising tool and obtain up to micrometer-level accuracy when combined with dual-comb interference. Applying this approach to underwater scenarios is feasible, but one must handle the issue that the ranging signal is significantly affected by environmental disturbances and system noises. However, it has been rarely reported that processing algorithms are tailored to the dual-comb signal to improve the quality of measuring signals. This article presents an enhanced underwater dual-comb ranging (DCR) solution via an improved variational mode decomposition (VMD). Specifically, we design a fitness function considering desired dual-comb interferogram characteristics. Accordingly, we optimize vital parameters and decompose the interested ranging signal to ensure final interferogram quality. Experiments verify that our method is superior to others and can improve the signal-to-noise ratio and restore the Gaussian-like shape of interferograms simultaneously. To the best of the authors knowledge, it is the first time DCR is boosted via VMD, and answers the question about interferogram shaping. The proposed solution may find important applications in ranging and imaging tasks underwater, as well as extend their working range and robustness against non-ideal environments.