# Two-Dimensional Permutation Vectors' (PV) Code for Optical Code Division Multiple Access Systems
## 6 Proof of Concept  
This section analyzes the performance of the proposed setup through system implementation in an optical networks simulation software called Optisystem. The proposed system architecture presented in Figures 6 and 7 was utilized to implement the simulation model for eight subscribers accessing the medium simultaneously. To deploy eight subscribers across the network, four spectral coding schemes and two temporal schemes were utilized. Consequently, the simulation model was implemented with \(\mathrm{K}_{1}=4,\;\mathrm{K}_{2}=2\) at g = 0, 1, 2, 3 and h = 0, 1. The OLT module was implemented in accordance with Figure 7, which shows a transmitter module configured at \(\mathrm{g}=0,\;1,\;2,\;\ldots,\;\mathrm{K}_{1}-1\) and h = 0. As mentioned earlier, for h = 0 in \(\mathrm{A}_{\mathrm{g,h}}\), all the spectral code sequences could be delayed by the same instant. Therefore, two LEDs followed by two temporal decoders were employed to configure encoding arrangements for eight subscribers accessing the medium simultaneously. Now, for h = 0, four subscribers were configured with a single broad-spectrum LED that related to time delay units through a 1:2 optical splitter having 0 dB loss. Both legs of the optical splitter were fed into time delay units that were configured in accordance with the position of 1s in the \(\mathrm{Y}_{0}^{\mathrm{T}}\) coding scheme. For instance, the TU connected with the top leg of the splitter was delayed by an amount of \(\frac{3}{\mathrm{Bit\ rate-8}}\), whereas the bottom TU was configured with the delay of \(\frac{5}{\mathrm{Bit\ rate-8}}\), respectively. Similarly for h = 1, the TUs were configured with the delays of \(\frac{6}{\mathrm{Bit\ rate-8}}\) and \(\frac{8}{\mathrm{Bit\ rate-8}}\) in accordance with the position of 1s at the \(\mathrm{Y}_{1}^{\mathrm{T}}\) coding scheme. The end face of the TUs were connected to a 2:1 optical combiner with 0 dB loss, followed by an EDFA module. Specification of the system components used during simulation analysis are given as Table 4. The amplified time-delayed signal from EDFA module related to a 1:4 optical coupler, in accordance with \(\mathrm{K}_{1}=4\). Each output leg of the coupler was fed into an individual MZM in order to modulate the signal with the user's information. After modulation, the process of spectral encoding was initiated by employing a combination of 1:2 optical splitter and MUX arrangement. MUX arrangement for each subscriber was configured to reflect the frequency bins in accordance with position of 1s in the \(\mathrm{X}_{\mathrm{g}}\) code sequence. Then, for user \(\mathrm{U}_{0,0}\), the spectral encoder allowed the spectrum located at \(\lambda_{3}\) and \(\lambda_{7}\), respectively. Similarly, for user \(\mathrm{U}_{0,1}\), a spectral encoding arrangement with same filter configuration was used to allow the spectrum located at \(\lambda_{3}\) and \(\lambda_{7}\), respectively. Consequently, the 2D temporal and spectral encoding operation for the coder word \(\mathrm{A}_{0,0}\) till \(\mathrm{A}_{3,1}\) was achieved at the transmitter module. Outputs from the spectral encoders were connected to an 8:1 optical coupler followed by 1:2 coupler having 0 dB loss and were configured in accordance with Figure 6. Moreover, two remote nodes were employed in the simulation model, in accordance with \(\mathrm{K}_{2}=2\). The ONT module for the simulation arrangement was configured accordingly to recover and detect the intended spectrum, in accordance with the proposed coding scheme. Each ONT module started with a 1:2 optical splitter to initiate the process of temporal decoding. Each leg of the splitter was fed to a TU with delays calculated through \(\mathrm{(S-1-j)}\). The end face of each TU related to a 2:1 optical combiner to conclude the process of temporal decoding. This process was followed by spectral decoding that was implemented with the help of balanced detectors. Balanced detectors split the incoming signal into two parts.