# Extending UWOC System Applications through Photon Transmission Dynamics Study in Harbor Waters
## 4 Conclusions  
This study has critically examined the UWOC within four distinct types of harbor water, employing the Monte Carlo method to simulate photon behavior and analyze key communication parameters. Our findings reveal that the Transmitted full divergence angle, received aperture, and FOV profoundly affect the UWOC system's performance. According to the simulation results, the following three main conclusions can be drawn:  
* Firstly, increased AL and divergence angle lead to higher received normalized power loss and time delay spread, the attenuation initially occurs at a rapid rate and then stabilizes, with these effects being more pronounced in clearer harbor water types.
* Secondly, this work reveals that the impact of communication distance on normalized power loss and time delay spread is more pronounced than that of water quality. This insight challenges that the common Beer-Lambert law no longer applies in  
Figure 13: Analysis of time delay spread in relation to attenuation length and received FOV across four harbor water. (**a**) Harbor I; (**b**) Harbor II; (**c**) Harbor III; (**d**) Harbor IV.  
-hardor water. Communication distance, estimated by simply dividing the attenuation coefficients of different water types in many studies, is ineffective in harbor water contexts.
* Consequently, increasing the received aperture and FOV, particularly over longer communication distances, contributes minimally to reducing normalized power loss or mitigating time delay spread, thus not significantly enhancing communication quality. Based on the fixed transmitted full divergence angle, the most suitable received FOV range is about 1-3.2 rad, and the most ideal received aperture is about 0.15-0.4 m. This result holds substantial technical relevance for the engineering design of UWOC across a range of harbor water conditions.  
It should be noted that this work simplifies the absorption and scattering models to facilitate analysis. We assume that the absorption and scattering characteristics of harbor water remain consistent throughout the photon's travel path. However, real-world water bodies may display more complex scattering and absorption behaviors due to dynamic water movements. This simplification represents a minor limitation of our study.  
All these insights and analysis results pave the way for more efficient design and optimization of UWOC systems, particularly in challenging harbor water environments, by providing a detailed understanding of the interplay between light scattering, absorption properties, and system configuration. Moreover, this study lays a technical and theoretical foundation that could facilitate the replication and expansion of our research into more turbid inland waters. Future research may develop more comprehensive models to accurately represent the diverse environmental conditions found in natural water bodies.  
Conceptualization, C.C. and X.X.; methodology, X.H.; software, G.L.; validation, P.L. ([PERSON]); formal analysis, W.N. and P.L. ([PERSON]); writing--review and editing, C.C.; visualization, C.L.; supervision, W.W. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Key R&D Program, grant number 2021 YFC2800504 and National Key R&D Program, grant number 2022 YFC2806001\(-\)2.  
Not applicable.  
Data available statement: Data are contained within the article.  
The authors thank the support from the State Key Laboratory of Transient Optics and Photonics, China.  
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.