# Evolutionary Strategy for Practical Design of Passive Optical Networks
## 6 Results  
The results are discussed in terms of genetic algorithm solutions and evolution, network optical power link budget and a comparison of the main information generated by the genetic algorithm. For centralized topologies, the green line represents the route of the feeder optical cable and the red diamond represents access splitters. For distributed topologies, the orange line represents the distribution cable. In addition, the red diamond represents first level splitters (distribution) and the black star represents second level splitters (access). Figure 5a,b (Figure 5c,d) show, respectively, the network initial state for non-dense and dense scenario, considering Region I with 314 nodes (and Region II with 714 nodes). This initial state will be used as an algorithm's input to find a solution for each one of the four considered topologies in this paper (as can be seen in details in Section 3). For non-dense scenario, an index of approximately 88 subscribers was obtained per km\({}^{2}\) for Region I (76 subscribers was obtained per km\({}^{2}\) for Region II). The number of generations was set, empirically, at 750. It was observed that, using higher values, there are no major changes in the final network total cost. For dense scenario, the incidence of nodes with seven subscribers in the initial state was predominant. An index of approximately 443 subscribers was obtained per km\({}^{2}\) for Region I (270.87 subscribers was obtained per km\({}^{2}\) for Region II). Again, it should be noted that subscribers were randomly distributed in the graph. Figure 9a-d (Figure 9i-l) shows the GA solutions for non-dense and Figure 9e-h (Figure 9m-p) for dense scenario in Region I (Region II), considering: (a) CTT1; (b) CTT2; (c) DTT1 and (d) DTT2. In CTT2, first level splitters are not represented (because they are placed at CO). Although considered in total cost, the last mile of cable is not represented in the figure to avoid too much data exhibition. Figure 10a,b and Figure 10c,d show, respectively, the GA evolution for each topology for the non-dense and dense scenarios, considering Region I Region II. As can be observed, there is a substantial reduction of the total network cost between the initial populations and the last ones. In addition, we can observe that negligible reductions are achieved if more generations are used. The stop criteria of 750 generations for Region I NDS and 1000 generations for Region I DS was set empirically. \begin{table}
\begin{tabular}{c c c c c} \hline
**Network Characteristics** & \multicolumn{2}{c}{**Region I**} & \multicolumn{2}{c}{**Region II**} \\  & **Values (NDS)** & **Values (DS)** & **Values (NDS)** & **Values (DS)** \\ \hline Initial population (individuals) & 125 & 125 & 125 & 125 \\ Number of generations (iterations) & 750 & 750 & 1000 & 1000 \\ Selection percentage (\%) & 40 & 40 & 40 & 40 \\ Reserve for future subscribers (\%) & 12.50 & 12.50 & 12.50 & 12.50 \\ Number of nodes & 314 & 314 & 714 & 714 \\ Total number of attended subscribers & 164 & 820 & 436 & 1544 \\ Nodes with 2 subscribers (green color) & 52 & 11 & 151 & 6 \\ Nodes with 4 subscribers (yellow color) & 8 & 35 & 21 & 19 \\ Nodes with 7 subscribers (red color) & 4 & 94 & 6 & 208 \\ Map area (km\({}^{2}\)) & 1.85 & 1.85 & 5.7 & 5.7 \\ subscribers/km\({}^{2}\) & 88 & 443 & 76 & 270.87 \\ \hline \end{tabular}
\end{table} 
Table 6: Network initial characteristics for Region I and Region II (with non-dense and dense scenarios). Figure 9: GA solutions for non-dense and dense scenario (with 314 and 714 nodes), considering four possible topologies (CTT1, CTT2, DTT1 and DTT2). **(a)** NDS-Region I-CTT1, **(b)** NDS-Region I-CTT2, (e) NDS-Region I-DTT1, **(d)** NDS-Region I-DTT2, **(e)** DS-Region I-CTT1, **(f)** DS-Region I-CTT2, **(g)** DS-Region I-DTT1, **(h)** DS-Region I-DTT2, **(i)** NDS-Region II-CTT1, **(j)** NDS-Region II-CTT2, **(k)** NDS-Region II-DTT1, **(l)** NDS-Region II-DTT2, **(m)** DS-Region II-CTT1, **(n)** DS-Region II-CTT2, **(o)** DS-Region II-DTT1, **(p)** DS-Region II-DTT2.