在彈性光網路中，保護之於恢復是一個相當重要的議題，除了一般在進行資料傳輸的工作路徑，還必須去執行繞徑調變與頻譜配置找出備用路徑，在保護機制中，共享備用路徑保護很常被討論，共享備用路徑保護使得備用路徑之間可以共用頻譜資源達到降低頻率槽使用量，而頻譜使用量有限，所以通常會直接影響到頻寬阻斷機率。
對於繞徑調變與頻譜配置來說，許多試探式演算法都去是以最短路徑或是最少節點數路徑為主，因而忽略掉需要頻率槽的數量及調變最大傳輸距離限制之間的平衡，因此，我們提出了一個共享備用路徑保護的演算法，名為最低權重優先集最短路徑演算法，去優先找最少節點數路徑並檢查其是否符合目前最高階調變最大傳輸距離，再考慮是否用需要被其他路徑取代，因而降低頻率槽的消耗量，另外還有嘗試去預先計算所有來源目的的所有小於最低調變方式的最大傳輸距離路徑，藉此去找出最少使用量的解，叫做最少使用量演算法。
此外，重組機制可以使頻譜資源配置狀況更整齊滑順，重新配置備用路徑可以降低碎裂問題及增加共享度，因此，我們提出共同鄰近及子路徑重組演算法去改善一些考慮共用路徑中時的缺失，節省資源消耗量。
數據結果顯示我們的演算法與比較的方法在頻寬阻斷機率有改善，頻譜使用率與執行時間都比較低，以及在重組的部分失敗機率也較低，並且探討在不同規模拓樸中不同方式的比較，以路徑長與最大傳輸距離選擇調變方式，還有不同批次量觸發重組的比較，以及碎裂程度的計算。

Protection is an important issue of resilience in elastic optical networks (EONs). Not only for working paths, but we have to do the routing, modulation and spectrum assignment (RMSA) for backup paths. In protection scheme, shared backup path protection (SBPP) is usually discussed now. SBPP allows backup paths share spectrum resource to reduce the used frequency slots. Spectrum usage critically effects bandwidth blocking probability (BBP) due to the limited resource in spectrum. For this reason, we aim at minimizing spectrum usage as our objective.
For the RMSA issue, many heuristic algorithms pursue the shortest path or minimum-hopped path and neglect the balance between number of required frequency slots and maximum transmission distance of modulation. Therefore, we propose a RMSA algorithm named lowest cost first and shortest path algorithm (LCF) to find the minimum-hopped path and check if it can meet the constraint of maximum transmission distance. So that the total consumption of frequency slots can be reduced. Another enhanced approach named minimum usage algorithm (MU) is to pre-calculate all paths for each source-destination pair so that the solution with minimum usage can be determined. In addition, reconfiguration can make spectrum resource smooth. Backup paths are re-allocated to reduce fragmentation problems and increase shareability. Thus, we also propose joint neighbor and sub- path reconfiguration algorithm (JNS) to improve a lack of consideration of shareable paths, saving frequency slot consumption.
Simulation results show that proposed algorithms achieve better BBP performance and spectrum utilization with significant reduction in execution time and reconfiguration failure as compared with previous work. Also, we demonstrate and discuss fragmentation ratio, the effect of topology scale and batch size of reconfiguration, and considerable modulation formats in different topologies.

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