一個新式的光學裝置在最新的文獻被提出來，其名為「可調變式光纖延遲線（VODL）」。正如其名，一VODL 的延遲時間可以被動態的調變設定在一特定的延遲時間範圍之內。一旦被設定好延遲時間，VODL 就可運作如同傳統的光纖延遲線去接收相等延遲要求的封包。因而，一VODL 可以被視為一伺服器，其服務時間恰為需要的延遲時間。
在這篇論文中，我們考慮的漏失系統由多條平行的VODL 所組成，其可以接收不同種類的封包。這樣的漏失系統跟傳統的漏失系統不同之處在於VODL 即使已被佔據，將仍可接收相同延遲時間的封包。在VODL 數目為無限多的情況下，我們證明了被多種不同種類的封包所佔用的VODL 數目仍然有著乘積型式的解。然而，對於有限數目的VODL 的分析就困難多了。對此，我們提出一基於狀態修截的求近似值的方法。我們驗證了用我們的求近似值的方法所計算出的封包漏失機率與實際模擬的結果非常相近。為了使此種漏失系統的封包漏失機率達到最小，我們也考慮了如何預先分配VODL 給各種類封包的方法。我們可以證明在網路流量低的時候，「完整分享」，也就是不預先分配任何的VODL 出去，為最佳的操作方式。在一般網路流量的情況下，我們提出一個貪婪搜尋演算法來找出絕佳的VODL 預先分配方式。模擬的結果證實了我們的貪婪搜尋演算法找出的解幾乎跟最佳解一樣出色。

Recently, a new optical device called variable optical delay line (VODL) has been proposed in the literature. As suggested by its name, the delay of a VODL can be dynamically set within a certain range. Once set, a VODL behaves like a traditional fiber delay line and can admit packets requiring the same delay as that set by the VODL. As in the queueing context, a VODL can thus be viewed as a
server that serves packets with the service times equal to the required delays.
In this thesis, we consider loss systems with parallel VODLs subject to various classes of packet arrivals. Such loss systems are different from the classical loss systems as a VODL, even occupied, can still admit new packets with the same delay. For the case with an infinite number of VODLs, we show that the number of VODLs occupied by different classes of packets still has a product form solution. However, the analysis for the case with a finite number of VODLs is much more difficult. For this, we propose an approximation method based on state truncation. We show that the packet loss probabilities derived from our approximation are very close to those generated from simulations. In order to minimize the packet loss probabilities in such loss systems, we also consider the problem of assigning dedicated VODLS to various classes of packets. We show under the light traffic condition, the complete sharing policy, i.e., the policy that does not assign any dedicated VODLs, is optimal. For the general traffic condition, we propose a greedy search algorithm to find a suboptimal assignment of dedicated VODLS. Simulation results show that our greedy algorithm yields very good assignments when comparing with the optimal ones.

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