## 5 Performance Evaluation
### Simulation Results
#### 5.2.1 Results for NSFNET
Additionally, Figure 6(b) shows the average number of inter-core crosstalk occurrences per lightpath establishment as a function of the offered load \(\rho\) in NSFNET with \(|\mathcal{C}|=3\) cores. In Figure 6(a), we can observe that the blocking probability of the LB method was the highest. On the other hand, as shown in Figure 6(b), the average number of inter-core crosstalk occurrences in the LB method was the lowest. This is because the LB method avoids the use of the same FSs in adjacent cores. However, this strategy also leads to an increase in the blocking probability. The FF method decreases the blocking probability in contrast to the LB method. Meanwhile, the FF method increases the number of inter-core crosstalk occurrences because it does not take into account inter-core crosstalk occurrences during the FS allocation process. In Figure 6(a), we can also observe that the blocking probabilities of the CP method and the proposed method with \(\gamma=1.0\) were almost the same as that of the FF method. Furthermore, the proposed method with \(\gamma=0\) exhibited the best performance in terms of the blocking probability. On the other hand, as shown in Figure 6(b), the number of inter-core crosstalk occurrences in the CP method and the proposed method with \(\gamma=0\) was higher than that in the LB method. This result indicates that assigning priority to cores is ineffective in reducing crosstalk when all cores are adjacent to each other. The proposed method with \(\gamma=1.0\) avoids the use of the same FSs in adjacent cores, similar to the LB method. Therefore, the number of inter-core crosstalk occurrences in the proposed method with \(\gamma=1.0\) was close to that in the LB method, even though the number \(|\mathcal{C}|\) of cores was small. Figure 7: Results in NSFNET (\(|\mathcal{C}|=3\)). We then evaluated the performance of our proposed RCSA method when the number \(|\mathcal{C}|\) of cores was increased, i.e., \(|\mathcal{C}|=7\) or \(13\). Figure 7(a),b show the blocking probability of lightpath establishment and the average number of inter-core crosstalk occurrences, respectively, as a function of the offered load \(\rho\) in NSFNET with \(|\mathcal{C}|=7\) cores. As shown in Figure 7(a), the blocking probability of the LB method was the highest, similar to the result in Figure 6(a). In contrast, the CP method and the proposed method with \(\gamma=1.0\) exhibited lower blocking probabilities than the FF method. The reason is that these methods suppress spectrum fragmentation by efficiently utilizing prioritized cores. We can also observe that the proposed method with \(\gamma=0\) exhibited the best performance in terms of the blocking probability. In Figure 7(b), we can observe that the FF method generated excessive inter-core crosstalk. On the other hand, the other methods efficiently reduced the number of inter-core crosstalk occurrences. The proposed method worked especially well when the offered load was small. This is because it selects cores so as to prevent inter-core crosstalk by appropriately setting the weight parameter \(W_{c}(R_{p})\) according to the required number \(R_{p}\) of FSs. We can also observe that the number of inter-core crosstalk occurrences was almost independent of the value of \(\gamma\) in the proposed method. This result means that the impact of the weight parameter \(W_{c}(R_{p})\) becomes more significant as the number of cores increases. Figure 8(a),b show the blocking probability of lightpath establishment and the average number of inter-core crosstalk occurrences, respectively, as a function of the offered load \(\rho\) in NSFNET with \(|\mathcal{C}|=13\) cores. In these figures, we can observe that the proposed method with \(\gamma=0\) achieved the best performance in terms of the blocking probability, similar to the previous results. On the other hand, the number of inter-core crosstalk occurrences in the proposed method was slightly larger than that in the CP method.