利用光正交分頻多工的技術，開發出了彈性光網路，並且使得頻譜資源變得更加得有彈性。彈性光網路提供了多個能收穫的優化維度來提高網路效率和生存能力。更具體的，在發生軟故障的情況下應用自適應調變格式選擇來解決故障。將現在的調變格式換成更加健全的調變格式來恢復QoT的惡化。因為選擇了更加健全的調變格式，頻譜需求變因此而增加。因此，光路便要重新被配置。在本論文中，光流量被定義為兩種類別，分別是速率保障型流量和最小速率保障型流量。再發生軟故障時，前者能拓展他的頻譜至後者。基於頻譜共享之繞徑與頻譜配置演算法是一種優化不同類別光路之間頻譜共享的演算法。我們提出了一種基於碎裂程度的頻譜配置策略和速率降低機制來解決SS-RSA問題。通過這些提出的技術，我們可以有效地降低網絡成本和得到大約85%~50% 的改善幅度。

With the optical orthogonal frequency division multiplexing (O-OFDM), elastic optical networks are developed, and spectrum resources become more flexible. EONs offer several optimization dimensions that can be harvested to increase network efficiency and survivability. More specifically, in a case of soft failure, the adaptation modulation format is applied to solve the failure. It changes the modulation format for a robust one which can recover the deterioration of QoT. Since the robustness of modulation format is selected, the spectrum requirement needs to increase. Therefore, the lightpath need to be reconfigured. In this thesis, optical traffic is defined as two classes, rate-guaranteed traffic and minimum rate-guaranteed traffic. The former traffic can expand their spectrum to the latter in a soft failure. Spectrum sharing RSA (SS-RSA) is an algorithm to optimize spectrum sharing among lightpaths of different classes. We propose a fragmentation-based spectrum policy and rate reduction mechanism to solve the problem of SS-RSA. By these proposed techniques, we can reduce the network cost effectively and get almost 85% ~ 50% improvement.

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