## 4 Results and Discussion
Figure 5: Scintillation index of a spherical wave versus the inner scale for different aperture diameters. Figure 1:0 Scintillation index of a spherical wave versus the inner scale for different wavelengths. The influence of the aperture averaging effect and anisotropic turbulence on the scintillation index is presented in Figure 1:1 Note that with or without aperture averaging in Figure 8 means whether the aperture averaging effect is used in the UWOC system or not. Obviously, the scintillation index decreases more sharply with the aperture averaging effect than that without the aperture averaging effect. This phenomenon is apparent when the inner scale is small. Furthermore, for a fixed value of \(\mu_{x}\) or \(\mu_{y}\), the anisotropic turbulence factor in the \(y\) or \(x\) axis contributes to the decrease of the scintillation index. The detailed variation of the scintillation index under various anisotropic turbulence factors with the aperture averaging effect is also given in the embedded subfigure, which further confirms our conclusions in Figures 4 and 5. Figure 1:2 Scintillation index of a spherical wave versus the inner scale with and without the aperture averaging effect for different anisotropic factors. Figure 1:3 Scintillation index of a spherical wave versus the inner scale under isotropic turbulence for different aperture diameters. Figure 9 demonstrates the effect of aperture diameter on the scintillation index under different anisotropic factors. The scintillation index decreases with increasing \(\mu_{x}\) or \(\mu_{y}\). In addition, the scintillation index decreases gradually as the aperture diameter increases, which is similar to Figure 1:4 Note that the scintillation index tends to be consistent when the aperture diameter is larger enough. Figure 10 depicts the influence of the inner scale \(L_{i}\) and outer scale \(L_{o}\) as a function of propagation distance \(L\) in anisotropic ocean turbulence. As shown in Figure 10, the scintillation index increases with increasing propagation distance, since the intensity fluctuations of the beam propagation in weak anisotropic turbulence increase and become increasingly more unstable. It can be seen from Figure 10 that there is a minimal effect of the outer scale on the scintillation index for a fixed inner scale when the propagation distance is considerable. However, there is a contrary trend for the inner scale, i.e., a larger inner scale leads to a smaller scintillation index. This phenomenon can be explained from a physical point of view: the outer scale of turbulence is much larger than the spot radius of the beam. The outer scale is a relatively uniform and stable medium for small beams. The inner scale of turbulence is smaller, and the change of the inner scale of turbulence per unit area is larger. Therefore, we conclude that the inner scale of the oceanic turbulence plays a more significant role than the outer scale in affecting the scintillation index in weak turbulent conditions. The effect of both inner and outer scales on the scintillation index is shown in Figure 1:5 It can be seen from this figure that in the case of weak turbulence, the outer scale has little effect on the scintillation index compared to the inner scale, which is similar to the previous conclusions [35; 50]. Figure 1:6 Scintillation index of a spherical wave versus the receiver aperture diameter for different anisotropic factors. The turbulence structure parameter is an influencing factor that affects the intensity of turbulence. Figure 12 analyzes the influence of the turbulence structure parameters, \(C_{n}^{2}\), on the scintillation index with aperture averaging of a spherical wave in the marine environment. The results show that the scintillation index increases with the increase of \(C_{n}^{2}\). This phenomenon is more obvious with the increase of the communication distance. Figure 1:7 Scintillation index of a spherical wave versus the inner and outer scales.