## 4 Discussion and Conclusions  
This research has investigated the impact of solar irradiation interference on optical inter-satellite links, focusing on the signal-to-noise ratio and path configuration simulations. The ideal case and solar-irradiance-affected cases for different field-of-view angles and transmission powers have been simulated. When the FoV is reduced to 1\({}^{\circ}\) or less, the signal-to-noise ratio is maintained despite interference from solar irradiance, with transmission \begin{table}
\begin{tabular}{c c c c} \hline \hline \(\boldsymbol{\sigma}\) & **Link Constraint** & **Link Loss** & **Distribution** \\ \hline \multicolumn{4}{c}{(a) Inter-plane} \\ \hline \multirow{2}{*}{0\({}^{\circ}\)} & 1000 km & 5.54\% & 7232/7656 \\  & 3000 km & 6.57\% & 50,236/53,768 \\ \hline \multirow{2}{*}{23.5\({}^{\circ}\)} & 1000 km & 11.60\% & 6768/7656 \\  & 3000 km & 11.59\% & 47,538/53,768 \\ \hline \multicolumn{4}{c}{(b) Inter-shell} \\ \hline \multirow{2}{*}{0\({}^{\circ}\)} & 1000 km & 10.82\% & 34,580/38,776 \\  & 3000 km & 8.85\% & 293,780/322,292 \\ \hline \multirow{2}{*}{23.5\({}^{\circ}\)} & 1000 km & 12.47\% & 33,942/38,776 \\  & 3000 km & 12.14\% & 283,154/322,292 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Link configuration information obtained under various conditions from ‘Seoul to London’. Part (**a**) represents the inter-plane, and (**b**) represents the inter-shell configurations. powers close to 1 W. However, for an FoV of 6\({}^{\circ}\), more transmission power (>10 W) is required to overcome solar irradiance. Using a multi-directional FoV model and Heron's-law-based categorization, the impacts of solar irradiance on inter-plane and inter-shell configurations have been investigated. The detour strategy, in two inter-continental scenarios, suggests that the inter-shell configuration outperforms the inter-plane one, reducing the overall path distance by up to 2500 km. Notably, because of the orbital inclination, inter-shell configurations exhibited higher link loss during summer in the northern hemisphere than inter-plane configurations; however, by offering more than five times the number of alternative paths, better performance is provided under solar irradiance. Although satellite laser communication terminals with high optical powers could mitigate the impact of solar irradiation, it is a challenging solution in space-based links, mainly because of high energy consumption, thermal management challenges, weights and costs, and a reduction in the satellite's lifespan. Consequently, future research should focus on developing models that minimize solar interference using lower transmission power, with the development of next-generation laser communication terminals, by applying an advanced machine-learning approach and energy-efficient and compact schemes, such as integrated sensing and communications (ISACs). Future work could explore the alteration vulnerability from the satellite attitude destabilization on the influence of solar irradiation through dynamic link modeling, providing deeper insights into the system's robustness. Conceptualization, J.S.H. and H.C.; methodology, J.S.H. ; software, J.S.H. ; validation, J.S.H., J.-Y.L. and H.C.; formal analysis, J.S.H. and J.-Y.L. ; investigation, J.S.H. ; resources, H.C.; data curation, J.S.H. and J.-Y.L. ; writing--original draft preparation, J.S.H. ; writing--review and editing, J.-Y.L. ; visualization, J.S.H. and J.-Y.L. ; supervision, H.C.; project administration, H.C.; funding acquisition, H.C. All authors have read and agreed to the published version of the manuscript. This research was supported by MSIT (the Ministry of Science and ICT), Korea, under the ITRC (Information Technology Research Center) support program (IITP-2025-RS-2023-00259061) supervised by IITP (the Institute for Information and Communications Technology Planning and Evaluation). Also, this research was supported by a National Research Foundation of Korea (NRF) grant funded by MSIT (RS-2023-00253346). Not applicable.