## 4 Simulation Results  
In this section, we present selected numerical and Monte Carlo simulation results to verify the accuracy of the derived expressions. The values of \(\alpha\) and \(\beta\) are set, similar to those adopted in [2], as \(\alpha=2.296\), \(\beta=2\) for strong turbulence, \(\alpha=4.2\), \(\beta=3\) for moderate turbulence, and \(\alpha=8.1\), \(\beta=4\) for weak turbulence. Moreover, \(\xi=1.1\) and \(\xi=6.7\) denote strong and weak pointing error effect levels, respectively. The general FSO links' parameters adopted for the simulations are as given in Table 1. Additionally, \(\omega=0.10168\) is considered for clear-air weather conditions and \(\omega=0.91095\) for light foggy weather conditions. Furthermore, it is assumed that \(\rho_{1}=\rho_{2}=\rho\) unless otherwise stated. Figure 3 gives a comparison of a single-hop (SH) FSO link, a non-EH DH FSO link, and the proposed SLIPT-based EH DH FSO link in terms of their OP performance metric. In order to present a fair comparison among the systems, let us denote \(P_{T}\) as the average power consumed by the communication system during \(T\) seconds. In this case, \(\mathcal{P}_{S}\) in (1) is given as \(\mathcal{P}_{S}=(2P_{T}/)(1+\tau)\). The analytical expressions for the SH FSO and the non-EH DH FSO links are obtained from [36] [Equation (12)] and [11] [Equation (5)], respectively. It can be seen from this figure that the proposed SLIPT-based EH DH FSO communication system outperforms the other two systems. It can also be observed from this figure that the SH FSO link presents the lowest OP performance among all considered \begin{table}
\begin{tabular}{l l} \hline
**Parameter** & **Value** \\ \hline Laser wavelength \((\lambda)\) & 1550 nm \\ FSO link distance \((L)\) & 2 km \\ Diameter of the APD & 20 cm \\ Responsivity \((R)\) & 0.9 \\ Optical-to-electrical conversion & 0.9 \\ coefficient \((\eta)\) & 25 mV \\ Thermal voltage \((V_{t})\) & 10 nA \\ Dark saturation current \((l_{0})\) & 1.3265 \\ LOS component’s average power & 1.3265 \\ of the optical signal \((\Omega)\) & 2 \(\times\) 0.1079 \\ Total scatter component’s average power of the optical signal \((2b_{0})\) & 0.596 \\ Amount of scattering power coupled & 0.596 \\ to the LOS component \((p)\) & \(\Phi_{A}=\pi\) \\ Deterministic angles & \(\Phi_{B}=\pi/2\) \\ \hline \end{tabular}
\end{table} 
Table 1: System’s simulation parameters. systems, and this is due to its lack of an intermediate relay node. For instance, an OP value of \(9.3\times 10^{-2}\) is obtained at \(\rho=20\) dB for the SLIPT-based EH FSO link. To acquire the same OP value, the non-EH DH FSO link requires an extra 5 dB, whereas the SH FSO link needs approximately an extra 9 dB of \(\rho\). Figure 4 presents the OP performance of SLIPT-based DH FSO links with different weather conditions and varying pointing error levels. It can be seen from the figure that the foggy weather conditions and high levels of pointing errors both deteriorate the OP performance, as expected. For example, at \(\rho=32\) dB, a link over a clear air and with a low level of pointing errors yields an OP value of \(1.5\times 10^{-3}\), while the same link but with a high level of pointing errors gives an OP value of \(3.1\times 10^{-2}\). Figure 5 exhibits a comparison of an SH FSO link, a non-EH DH FSO link, and the proposed SLIPT-based EH DH FSO link in terms of their ergodic capacity performance. The analytical expressions for the SH FSO and the non-EH DH FSO links are obtained from [36] [Equation (28)] and [11] [Equation (27)], respectively. It can be observed from this figure that the proposed SLIPT-based EH DH FSO link has a superiority in performance over the other two communication links. For instance, at \(\rho=32\) dB, the proposed SLIPT-based EH FSO link yields an ergodic capacity of 5.97 bits/s/Hz, whereas the non-EH DH FSO and SH FSO links give ergodic capacity values of 3.811 bits/sec/Hz and 3.29 bits/s/Hz, respectively.