| Summary: | The Angle of Arrival (AOA) fluctuation caused by oceanic turbulence is the critical factor affecting the performance of underwater communication and imaging systems. Based on the general Oceanic Turbulence Optical Power Spectrum (OTOPS), this paper derives analytical solutions for the full interval of the Wave Structure Function (WSF) and the AOA fluctuation variance of the Gaussian beam using the Rytov approximation method applicable to weak turbulence conditions. The approximate solutions of the above physical quantities and the Spatial Coherence Radius (SCR) in the asymptotic intervals of large spacing (<italic>ρ</italic>≫<italic>η</italic>, where <italic>ρ</italic> denotes spacing and<italic>η</italic> denotes Kolmogorov microscale) and small spacing (<italic>ρ</italic>≪<italic>η</italic>) are also discussed. The numerical results show that the existing results have a large deviation around the Fresnel ratio <italic>Λ</italic><sub>0</sub>=1 when <italic>ρ</italic>≫<italic>η</italic>. On the basis of this, the relationship between AOA fluctuation variance and<italic>ρ</italic>/<italic>η</italic> is also analyzed. In the asymptotic interval <italic>ρ</italic>≪<italic>η</italic>, the AOA fluctuation variance is almost constant. When in the interval <italic>ρ</italic>≈<italic>η</italic>, the AOA fluctuation variance decreases sharply. When in the asymptotic interval <italic>ρ</italic>≫<italic>η</italic>, the decline of the AOA fluctuation variance becomes gradually flat. The results derived in this paper are more accurate and applicable to a wider range. These results will enable a better study of the propagation properties of Gaussian beams in weak oceanic turbulence.
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