# Research on Underwater Wireless Optical Communication Channel Model and Its Application
## 3 Underwater Optical Wireless Communication Experiment
### Experimental Results and Discussion  
In this study, wireless optical communication experiments were conducted at four distinct locations with varying water qualities, namely a pond, The Qipan Mountain, The Guanshan Lake, and Benxi. Table 3 lists the attenuation coefficients for different water qualities, along with the corresponding maximum optical communication ranges and associated bit error rates (BERs). Figure 4: Schematic diagram of measuring platform. Figure 5 presents the relationship between water quality (attenuation coefficient) and the maximum communication range, assuming a constant optical-electrical loss in model (6), with the consideration that the received power has an accuracy range of \(\pm\)10%. The data points represent the experimental results, while the solid line represents the model prediction. From Figure 5, it is evident that the experimental data and the model demonstrate good agreement at a medium range but exhibit centimeter-level discrepancies at both short and long ranges. The model's error is dependent on the range, and we speculate that this discrepancy can be attributed to the effects of multipath and environmental light. At longer communication ranges, the channel experiences more interference, causing the actual transmission range to be lower than the model predictions. Conversely, at shorter communication ranges, the impact of interference on optical communication is minimal, resulting in the actual transmission range being higher than the model predictions. Figure 6 illustrates the effective communication space for different spatial configurations of the transmitter and receiver under various water qualities, as simulated using model (9). These simulations take into account received power with an accuracy range of \(\pm\)10%. The transmitter is positioned at the origin along the \(Z\)-axis, while the \(X\)-axis and \(Z\)-axis represent the relative position of the receiver, oriented parallel to the transmitter but not aligned with it. The red and orange curves in the graphs represent received sensitivities of \(-\)26.4 dBm and \(-\)22.4 dBm, respectively. The black and blue dots in the graphs represent actual data points collected during the experiments, with black indicating successful com  
Figure 5: Effective communication ranges for different water quality conditions (with different attenuation coefficients). \begin{table}
\begin{tabular}{l l l l l l} \hline \hline \multirow{2}{*}{**Number**} & \multirow{2}{*}{**Place**} & \multirow{2}{*}{**Attenuation Coefficient**} & **Measured Max** & **Calculated Max** & **BER (Max** \\  & & **Communication Range (m)** & **Commication Range (m)** & **Commication Range (m)** & **Commication Range \\ \hline
1 & Pond & 0.24–0.82 & 9.8 & \textgreater{}20 & 3.05 \(\times\) 10\({}^{-5}\) \\
2 & The Guanshan Lake & 2.2–2.8 & 4.2 & 4.02–5.00 & 3.12 \(\times\) 10\({}^{-5}\) \\
3 & Benxi & 5.1–5.7 & 2.4 & 1.82–2.43 & 3.02 \(\times\) 10\({}^{-5}\) \\
4 & The Qipan mountain (25 m from the shore) & 6.8–7.3 & 1.9 & 1.45–1.88 & 3.11 \(\times\) 10\({}^{-5}\) \\
5 & The Qipan mountain (near the shore) & 10.2–10.6 & 1.7 & 0.94–1.12 & 3.20 \(\times\) 10\({}^{-5}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The parameters of optical communication. munication and blue indicating failures. To simplify the plot, only the most critical data points are displayed. During experiments conducted in the pond, the receiver was moved at 2 m intervals along the \(Z\)-axis to account for long range. However, in the lake environment, the receiver was moved at 1 m intervals to ensure a more accurate analysis. This change in the interval between the pond and lake experiments allows for a more comprehensive assessment of communication performance and behavior in different scenarios. The experimental data indicate that the error between the measured values and the model predictions is small for the medium communication range in the lake water, with differences in the communication range being maintained within approximately 10 cm.