Influence of upper ocean bubbles on blue-green laser uplink cross-media transmission

Laser cross-media transmission through seawater, the air-sea interface, and atmospheric channels experiences various effects, including spatial and temporal dispersion arising from intrinsic laser divergence and medium scattering, and received power reduction induced by medium absorption. These effects result in a lower signal-to-noise ratio and a limited maximum signal bandwidth. Consequently, channel loss is closely related to the channel transmission characteristics. This paper employs the Monte Carlo simulation method to systematically investigate the effects of upper ocean bubbles on uplink cross-media laser transmission under various conditions. The optical properties of upper ocean bubbles are determined by the latest bubble size distribution model based on Mie scattering theory. The influence of bubbles on laser transmission characteristics is examined through changes in angle of arrival (AOA) distribution, spot intensity distribution, and power loss, which vary with water quality, depth, and wind speed. The results indicate that high-concentration bubbles induce changes in the optical properties of the upper ocean water, thereby exerting a significant influence on laser transmission under high wind speed conditions in clear, shallow waters. For instance, the presence of bubbles increases the spot size by 30% and reduces the received power by 4 dB at a wind speed of 18 m/s. Furthermore, the influence of bubbles on laser transmission characteristics exhibits complex and non-monotonic behavior that varies with water quality and depth conditions. The results reveal the effects of bubbles on uplink cross-media laser transmission under various conditions, quantitatively assessing the impacts on key parameters, such as laser AOA, spot size, and power loss induced by upper ocean bubbles. These findings can provide a solid foundation for the development of advanced blue-green laser-based cross-media wireless communication systems.