雖然多波長分工 (WDM) 技術已經被引入在網路運作有一段時間， 但是服務提供商之間的競爭日漸激烈，因此提供一個更可靠及更具彈性的光網路需求，不久之後將會迅速增加。 尤其，在恢復因網路元件故障所導致失效的連線。
　　
　　文分中提出兩個方法用來建構一個可靠的分光多波長分工網路：備用重組的波長繞路法的技術(wavelength routing technique with spare reconfiguration)以及環形分解法(cycle decomposition)。使用波長繞路法的方法中，一般以路徑保護共享備用光路徑(path protection using shared spare lightpaths)可在需要最小的備用資源情形之下改進阻斷機率(blocking probability)。但是在動態的環境下，這個方法會因備用光路徑波長連續性而無法配置給新的工作光路徑而導致效能下降。本文提出波長重配置(SR_WR)與路徑重配置(SR_PR)的備用重組機製，使得備用光路徑可動態改變以降低阻斷機率。

　　有向環形分解演算法(Directional Cycle Decomposition Algorithm DCDA)可以事先決定所有節點之間的路徑，使得光纖網路中可以容許最大數量的錯誤(大於等於1)。DCDA主要是將尋找網路中可以容許的最大數量轉換成環形覆蓋問題並且使用簡單的loop-back機製來恢復受阻的光路徑(lightpath)。從結果來看，DCDA可以被用於各式各樣的網路拓樸且只增加每一個光路徑中少量的距離。

　　Although the WDM technology has been introduced into networking for some time, the demands for survivable and flexible optical networks will increase more rapidly in the near future due to the intense competitions among service providers. In particular, restoration of services within a short period of time after a link or node failure is becoming a requirement.

　　In this paper we evaluate failure survivability based on spare reconfiguration (SR) for single-link failure and cycle decomposition for multiple-link failures on all-optical WDM mesh networks. The technique of spare routing is to construct dependable all-optical WDM networks. Path protection using shared spare lightpaths is a general wavelength routing method to improving the blocking probability while minimizing the required spare resources. However, in a dynamic traffic environment, this method may still lead to poor performance because it is highly likely that a wavelength on a link is continuously held by a spare lightpath and can not be assigned to the working lightpath of a new connection. This paper presents a spare reconfiguration mechanism with wavelength reassignment (SR_WR) and path reassignment (SR_PR) to make the spare dynamic and thus to further reduce the blocking probability.

　　The problem of finding the maximum number of faults that can be tolerated is modeled as a constrained ring cover set problem, which is a decomposition problem with exponential complexity. The Directional Cycle Decomposition Algorithm (DCDA) that can tolerate one or more faults is proposed. To restore the failure link(s) are based on a simple loop-back mechanism implemented directly in the optical layer to ensure fast restoration with little coordination overhead. From the results, we know that the maximum number of faults tolerated can be extended from one significantly under various network topologies.

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