## 7 Network Simulation and Discussion
Firstly, the received signal is divided and sent to the delay line for the temporal decoding according to the temporal sequence, then to the spectral decoder FBG for the spectral decoding according to the spectral sequence, secondly, the decoded impulses are sent to the photo-detector for conversion into electrical signals, and finally, the output electrical signals are sent to the low pass Bessel filter in order to filter the unwanted signals and keep useful signals. Figure 16 shows the opening of the eye diagrams of eight users where the data rate equals 1 Gbps; according to the figure, we note that the eight users have a maximum vertical opening, which indicates that the proposed code offers better performance and that the data transmitted are received almost as the data that are sent. Our code offers a quality  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Subcarriers**} & \multicolumn{3}{c}{\(\mathbf{X_{g}^{T}}\)} & \multicolumn{3}{c}{\(Y_{h}\)} & \multicolumn{3}{c}{\(Z_{L}\)} & \multicolumn{3}{c}{**3D-VWZCC**} \\ \cline{2-11}  & \(\lambda_{1}\) & \(\lambda_{1}\) & \(\lambda_{3}\) & \(\lambda_{4}\) & \(t_{1}\) & \(t_{2}\) & \(t_{3}\) & \(t_{4}\) & \(C_{1}\) & \(C_{2}\) & \(C_{3}\) & \(C_{4}\) & \\ \hline \(\upsilon_{1}\) & & & & & & & & & & & & \\ \hline \(\upsilon_{2}\) & &factor Q, which reaches between 9 and 11.56 with a BER reaching between \(7.85\times 10^{-20}\) and \(1.99\times 10^{-31}\) at a high data rate. To strengthen and prove these results, Figures 17 and 18 show the eye diagram of one of users at a data rate of 1 Gbps and 2 Gbps, respectively. Moreover, the user providing 1 Gbps of data rate shows a quality factor reaching 11.56 and corresponds to a BER of \(1.99\times 10^{-31}\), whereas the user who provides 2 Gbps of data rate can reach a quality factor of 9.45 with a BER equal to \(7.96\times 10^{-22}\); hence, we explain these results by the high efficiency offered by our code at a high data rate despite the existence of a high number of users, due to low impact of MAI effect and PINN noise, and this is thanks to the zero cross-correlation property of our code. In addition to that, the primary principle of the interpretation of the eye diagram is to evaluate the aperture regardless of whether it is vertical or horizontal in terms of BER and quality factor Q; in addition to that, other parameters are also considered, such as jitter, noise margin, and time sensitivity. For that, from Figures 17 and 18 we evaluate the following parameters: firstly, in terms of jitter, we notice that the jitter of the eye diagram of our code is very low. Secondly, in terms of noise margin, the eye-opening is at the maximum, which indicates that the signal-to-noise ratio SNR is very high and the noise power is very low; this due to the ZCC property of 3D-VWZCC code, which suppresses PINN noise. Finally, in terms of time sensitivity, the time-sensitivity slope of the eye is small, which indicates that the sensitivity to synchronization error is very low. In summary, the proposed 3D-VWZCC code demonstrates a high immunity against transmission errors due to zero cross-correlation properties, which totally ignores multiple access interference (MAI) and reduces PINN noise. Figure 17: Diagram of the first user’s eye at 1 Gbps. Figure 18: Diagram of the first user’s eye at 2 Gbps.