# Research on Underwater Wireless Optical Communication Channel Model and Its Application
## 3 Underwater Optical Wireless Communication Experiment
### Experimental Setup
The close alignment between the curves suggests a significant resemblance between the observed radiation intensity distribution and a centrally symmetric Gaussian distribution. Consequently, in model (9), Equation (10) is utilized to calculate the function \(f(\theta)\). \[f(\theta)=e^{\frac{-(\mu-\mu)^{2}}{2^{2}}},(\mu=0,\sigma=14.53) \tag{10}\]  
A measurement platform was specifically designed for the test site. This platform served the purpose of fixing the underwater wireless optical communicator transmitter. The receiver was connected to the measurement slider, which could move freely in the X-Z plane on a rail. The rail was fixed with a scale and the pointer was on the slider. The measurement platform was 15 m long in the Z direction, 7 m long in the Y direction, and 6.3 m long in the X direction. This ensured sufficient space for conducting experiments and positioning the transmitter and receiver at the desired depths underwater. The entire experimental system, as shown in Figure 4, comprised several components. These included \begin{table}
\begin{tabular}{l l} \hline \hline
**Parameters** & **Values** \\ \hline Light source & LED \\ Optical transmit power & 6 W (radiometric) \\ Optical wavelength & 450 nm (royal blue) \\ Emitter beam shape & 45\({}^{\circ}\) (half angle) \\ Receive beam shape & 45\({}^{\circ}\) (half angle) \\ Dimensions (length \(\times\) diameter) & 264 \(\times\) 128 mm \\ Receiver detector & Photomultiplier tube (PMT) \\ Receiving sensitivity & \(-\)24 dBm \\ Data rate & 1–5 Mbps \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Parameters of optical communication. Figure 3: Relative radiation intensity distribution of the light source. the transmitter, receiver, signal-transmitting PC, signal-receiving PC, underwater cable, and two power supplies. Both the transmitter and receiver were located 7 m underwater and were connected to the power supply and test equipment ashore via underwater cables. This setup enabled the transmission and reception of signals between the underwater devices and the shore-based equipment, facilitating the measurement and analysis of the optical communication performance. By varying the position of the receiver of the optical communication device along the X and Z axes in specific increments, changes in communication status were observed to determine the maximum communication range and the effective communication space. To measure the maximum communication range, the transmitter was kept parallel and aligned with the receiver. The transmitter was fixed at coordinates (0,0,0) and the receiver was translated in a straight line at X = 0 and Y = 7. Initially, the receiver was moved along the Z-axis at a spacing of 1 m until the results of the two measurements before and after were successful and unsuccessful, at which point the slider was moved at intervals of 0.1 m instead, and the maximum Z value of the receiver that could complete the communication was recorded. For measuring the effective communication space, the transmitter and receiver were still kept parallel, but they were no longer aligned. The transmitter remained fixed, while the receiver was moved at different Z-axis distances for the X-axis movement. The process began with initial displacement to a distance of 1 m for approximate measurements. Subsequently, the receiver was adjusted at intervals of 0.2 m to facilitate precise measurements. This systematic approach enabled the accurate determination of the final effective communication space.