Predictive mechanisms for underwater laser backward detection channel in bubble-induced turbulence

Bubble-induced turbulence poses tremendous challenges to the stability of underwater laser backward detection channels, accuracy of detection information, and resolution of detection systems. Majority of the existing methods are adopted from the research on laser forward transmission channels in underwater wireless optical communication. However, owing to the different reception modes of the two, coupled with the complexity and variability of the underwater backward scattering channel, the forward transmission channel method is not suitable for characterizing the change of laser backward detection channel.. Based on the spatiotemporal distribution law of the underwater bubble field and laser backscattering theory, a weighted predictive mechanism for the laser backward detection channel under the induced turbulence of an asynchronous mixed bubble layer is proposed. Using this mechanism, the distribution characteristics of the intensity fluctuation of a backward laser detection channel under bubble-induced turbulence were studied statistically and experimentally. The spot scintillation coefficient (SI) was introduced to quantify the effects of the bubble density and scale on the laser backscatter intensity. A goodness-of-fit test was performed based on the correlation coefficient (R²) and root mean square error to verify the accuracy of the model, and the effect of mixed bubble-induced turbulence on the laser backward detection channel was quantified. The results show that the model has 95 % fitting degree at 50–1000 μm bubble size and 100–2000 cm⁻³ bubble density, and the change in bubble size-induced turbulence has a greater effect on channel intensity fluctuation compared to the change in bubble density-induced turbulence. These results provide a potential theoretical application of underwater LiDAR detection.