在科技的日益進步下，使用群播傳輸資料的情形也相對地增加，且對於網路傳輸量也有大量需求。利用光正交頻分多工的技術，彈性光網路在資源分配的單位由波長變為粒度較小的頻率槽，相較於波長分波多工光網路，能更有效地分配頻譜資源。
群播在之前的許多研究中經常被提出來討論，以往光網路在做分光時需要使用光電轉換，導致消耗大量的能量，因此若是每個節點皆具有分光能力將會造成大量花費。另一方面，若是每個節點皆具有轉換能力，會經過許多接、收發器，進而產生許多花費，因此我們提出一種具稀疏分光能力及波長轉換的虛擬源方法。
而在距離可調適型的彈性光網路下，決定適當的調變格式及傳輸路徑能有效地配置頻譜資源，進而讓其他傳輸需求更有機會被服務。在彈性光網路中使用虛擬源能夠打破傳輸距離的限制，不會因為傳輸需求欲傳輸的距離超過網路環境提供的最遠傳輸距離限制而造成傳輸失敗，且能盡可能地選擇較高階的調變格式並打破不同鏈路間的頻譜連續性限制，使得使在使用頻譜資源上更有效率。
另外在具稀疏分光能力的彈性光網路中，虛擬源的配置方式是很重要的。我們提出虛擬源的配置方法，並調整虛擬源的配置數量，能夠發現在適當的節點上配置虛擬源能夠使得資源的使用情形在傳輸上更有效率。而頻譜資源的配置策略在光網路中也是一項重要的議題，我們使用不同的配置策略並比較其頻譜資源使用情形，在實驗數據的表現上，虛擬源的配置方法部分ND在表現上是最佳的，而DA是最差的，在頻譜資源的配置策略部分，使用層化圖策略雖然能夠得到較好的需求阻斷率，但卻會花費較多的執行時間，而使用群集、子群集方法能夠有效降低頻譜配置的計算時間，但由於碎裂的產生會使得需求阻斷率差於層化圖策略。

Nowadays, multicast services gain popularity with the large requirements on network traffic. To address the growth of multicast messages, we may use more hardware like splitters and conversions to support. However, in full splitting network, using too many splitters and conversions would lead to more cost. We focus on sparse splitting and conversion capable for the multicast traffic in Elastic Optical Networks (EONs) considering distance-adaptive transmission and propose virtual source (VS) node which has been used in WDM.
In distance-adaptive EON, we can assign the spectrum resources efficiently by trying to use a higher-level modulation format and select an appropriate routing path. Besides, using VS nodes can prevent the requests from being blocked by the maximum transmission distance (MTD) constraints. In addition, VS nodes can convert spectrum and re-modulate to improve the spectrum efficiency.
However, placing VS node appropriately on topology is an important issue, we also propose the placements of VS node and adjust the number of VS nodes to control the cost. Also, spectrum assignment strategy is an important issue in EONs, we use several spectrum assignment strategies and compare their performance. About the placements of VS node, simulation results show that the ND placement is better than TW and DA, and the DA placement is the worst. About the assignment strategies, we can obtain better BP by using layered-graph, but it takes more execution time. Using cluster and sub-cluster can save more time, but due to the fragmentation, the BP of cluster and sub-cluster are higher than that of layered-graph.

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