## 5 Numerical Results
Figure 6 also shows that the SOP of the hybrid system will increase with the increase of turbulence intensity, whether FSO link eavesdropping or RF link eavesdropping. Therefore, it can be seen that whether FSO link eavesdropping or RF link eavesdropping, the turbulence intensity has an obvious impact on the SOP of the hybrid system. When the turbulence intensity is the same, the SOP of the system with RF link eavesdropping is higher than that with FSO link eavesdropping. It can be seen from Figure 5 that the capacity of the hybrid system is the highest, the only RF system is the second, and the only FSO system is the lowest. Therefore, the instantaneous security capacity of the hybrid system with RF eavesdropping is smaller than that with FSO eavesdropping. It is further known that the SOP of the hybrid system with RF eavesdropping is larger than that with FSO eavesdropping. Assuming moderate turbulence and a target rate of \(0.1\) bit/s/Hz, (\(\alpha_{m}=2\), \(\mu_{m}=1\)), \(\overline{\gamma}^{RF}=10\) dB, \(\xi=2\), and \(\xi^{E}=1\), Figure 7 describes the relationship between the SOP of the hybrid system with FSO link eavesdropping and RF link eavesdropping and the average SNR of the FSO channel under the different average SNR of eavesdroppers. When the average SNR of the eavesdropper increases, the SOP of the hybrid system increases accordingly. For example, when the average SNR of the FSO channel is \(5\) dB and \(\overline{\gamma}^{E}=-5\) dB, the SOP of the hybrid system with RF link eavesdropping and FSO link eavesdropping is \(1.87~{}\times~{}10^{-3}\) and \(5.927~{}\times~{}10^{-4}\), respectively; when average SNR of the FSO channel is \(5\) dB and \(\overline{\gamma}^{E}=0\) dB, the SOP of the hybrid system with RF link eavesdropping and FSO link eavesdropping is \(2.16~{}\times~{}10^{-2}\) and \(7.809~{}\times~{}10^{-3}\), respectively. Assuming moderate turbulence, (\(\alpha_{m}=2\), \(\mu_{m}=1\)), \(\overline{\gamma}^{RF}=10\) dB, \(\overline{\gamma}^{E}=0\) dB, \(\xi=2\), and \(\xi^{E}=1\), Figure 8 describes the relationship between the SOP of the hybrid system with FSO link eavesdropping and RF link eavesdropping and the average SNR of the FSO channel under different target rates. The SOP of the hybrid system with RF eavesdropping link is higher than that of the FSO eavesdropping link. Whether FSO link eavesdropping or RF link eavesdropping, the SOP of the hybrid system further increases with the increase of the target rate. This is because when the target rate is increased, the SOP of the hybrid system also increases. Figure 5: Relationship between channel capacity and SNR of the hybrid system, only FSO system and only RF system under different pointing errors and moderate turbulence. Figure 6: Underdifferent turbulence intensity, the relationship between the SOP of the hybrid system with RF and FSO link eavesdropping and the average SNR of the FSO channel. Figure 7: Under different \(\overline{\gamma}^{\rm E}\) conditions, the relationship between the SOP of the hybrid system with RF and FSO link eavesdropping and the average SNR of the FSO channel. Assuming moderate turbulence (\(\alpha_{m}=2\), \(\mu_{m}=1\)), \(\overline{\gamma}^{RF}\) = 10 dB, \(\overline{\gamma}^{E}=0\) dB, and \(R_{s}=0.1\) bit/s/Hz, Figure 9 describes the relationship between the SOP of the hybrid system with FSO link eavesdropping and RF link eavesdropping and the average SNR of the FSO channel under different \(\xi\) and \(\xi^{E}\). It can be seen from Figure 9 that whether it is FSO eavesdropping or RF eavesdropping, the SOP of the hybrid system decreases with the increase of \(\xi\). According to Figure 5, as \(\xi\) increases, the capacity of the hybrid system also increases, so the SOP of the hybrid system with RF or FSO eavesdropping decreases.