近年來，隨著高速多媒體應用的出現，例如：視訊會議、隨選視訊等，使得網路訊務大量增加。以分波多工技術為基礎的光網路之高頻寬特性可以滿足此需求。而這些新興的多媒體應用都需要使用群播技術以完成資料的傳輸，因此，必須在光網路中提供群播傳輸服務。
波長是光網路中重要的資源之一，因此波長分配的恰當與否將會是影響光網路容量的主要因素。相關研究指出使用波長轉換可以更有效地使用波長進而提升網路有效使用率，但是波長轉換器較為複雜且成本較高，所以在網路架構設計時所使用的波長轉換器是有限的。
在本論文中，我們分析在具有限數量波長轉換器的分波多工網路上的群播連線之波長分配，並以計算影響網路容量多寡的方式來分析不同的波長分配對網路的影響。本論文透過分段的方式提出影響最小優先(Minimum-Effect-First)的波長分配方法，利用此方法選擇群播路徑之波長，可降低對網路容量的影響。同時我們也將模擬結果與首次適合(First-Fit)及隨機(Random)選取等波長分配的方法進行網路容量減少多寡的比較。由模擬結果看出，無論在任何情況下，本論文所提出的影響最小優先的波長分配方式都可以得到較佳的效能。

Recently, the advent of high-speed multimedia applications, such as video-conferencing and video-on-demand, has made internet traffic increased dramatically. By using Wavelength Division Multiplexing, optical links provide higher capacity than traditional network and can meet the ever-increasing demand for bandwidth. Those applications need multicast to deliver information for multiple destinations simultaneously, so the multicast capability in optical network is required.
Wavelength is one of important resource in optical network. Wavelength assignment is mainly an influential factor that affects the network capacity. Employing wavelength conversion can arrange wavelength more effectively to increase network utilization. But the wavelength converter is still complex and expensive. Thus, currently, it is not possible to have all network nodes be equipped with wavelength conversion capability. The number of wavelength converters is finite in practical design of network architecture.
In this thesis, we analyze multicast wavelength assignment in DWDM network with finite wavelength converters nodes and analyze network state for different wavelength assignment by calculating network residual capacity. We propose a Minimum-Effect-First (MEF) wavelength assignment algorithm to decrease the effect of effective network capacity. We compare MEF to First-fit and Random on network capacity. The experimental results demonstrate that the proposed MEF scheme illustrates better performance than First-Fit and Random in any condition.

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