# Enhanced Spectral Amplitude Coding OCDMA System Utilizing a Single Photodiode Detection
## 4 Results and Discussion
### Presence of DCF and EDFA  
As discussed, the system performance was improved leading to a better BER in the presence of EDFA only or DCF only in a SAC-OCDMA system using EDW codes as signature codes. Subsequently, we examined performance in terms of BER, Q-factor, and received power for the SAC-OCDMA system using different codes in the presence of both DCF and EDFA with SPD detection techniques (Figure 9). It is clear that using MDW codes gives a better BER than using EDW codes at 622 Mbps and 1 Gbps. At 2 Gbps, the system using MDW codes and that using EDW codes nearly have the same value of BER. In general, as shown, it is preferable to use the system with MDW codes, as it has a better performance at different transmission distances and different bit rates. Figure 7: BER with transmission distance of SAC-OCDMA system using EDW codes with APD detector, PIN detector, and PIN detector in the presence of EDFA. Figure 10 displays a comparison between the received powers of the SAC-OCDMA system using different codes and SPD detection technique at different data rates and different transmission distances  
Figure 8: Eye diagram for one user of SAC-OCDMA system using EDW code, sending bit rate of 622 Mbps at 100 km using PIN detector in presence of EDFA. Figure 9: BER with transmission distance for SAC-OCDMA using different codes and SPD detection technique at different bit rates in the presence of DCF and EDFA. in the presence of DCF and EDFA. It is noticed that as the transmission distance increases, the BER increases and the system using MDW code receives greater power than that with EDW codes. Table 4 summarizes and compares the present results and previous work, concerning the BER of the SAC-OCDMA system using different signature codes with PIN detector at different transmission distances and different bit rates. A fair agreement is noticed. Moreover, higher bit rates lead to an increase in BER. Figure 11 represents a comparison for the Q-factor using different codes and SPD detection technique at different data rates and different transmission distances in the presence of both DCF and EDFA. Clearly, the Q-factor decreases with the transmission distance, and using MDW code yields a higher Q-factor than using EDW code. Finally, it is worth noting that all the obtained results for the proposed system are designed and simulated using Optisystem ver. 7. The practical implementation for such a system can be also attainable due to the availability of all utilized components and equipments commercially and in laboratories. However, power losses and noise effects should be considered when obtaining experimental results. It is also important to highlight that these results were obtained using transmission speeds up to 2 Gbps and two different codes. Higher speeds will limit the performance of the proposed system, while other codes can change the complexity and hence the limitations of such system. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Transmission Distance (lam)**} & \multicolumn{2}{c}{**BER**} \\ \cline{3-6} \multirow{-2}{*}{**Spectral Amplitude Coding-optical Code Division Multiple Access (SAC-OCDMA) System Using Different Codes**} & **Using Modified Double Weight (MDW) Codes** & **Using Enhanced Double Weight (EDW) Codes** & **Bit Rate** & **Using MDW** & **Using EDW Codes** \\ \hline \hline \multirow{2}{*}{**In absence of EDFA and DCF**} & Ref. [24] & 60 & NA & 622 Mbps & \(1\times 10^{-20}\) & NA \\  & 60 & NA & 1.25 Gbps & \(1\times 10^{-15}\) & NA \\ \hline \hline \multirow{2}{*}{**In presence of EDFA only**} & Ref. [22] & 140 & NA & 622 Mbps & \(1\times 10^{-10}\) & NA \\  & 144 & 144 & 622 Mbps & \(8\times 10^{-14}\) & \(1.01\times 10^{-18}\) \\ \multirow{2}{*}{**In presence of EDFA and DCF**} & \multirow{2}{*}{Present work} & 120 & 144 & 1 (Gbytes & \(4.43\times 10^{-15}\) & \(1.72\times 10^{-9}\) \\  & & 120 & 120 & 2 Gbps & \(5.51\times 10^{-10}\) & \(2.5\times 10^{-9}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Bit error rate (BER) summary and comparison.