近年來，在使用交換延遲線來建造無衝突(Conflict-Free)光纖佇列(Optical Queues)的發展上，有著無數的進展。許多無衝突光纖佇列是用2x2的交換機所組成，也因此會遭遇所謂的串音(Crosstalk)問題。為了減少這個串音問題，在文獻中建議我們應該避免兩個封包，在一個2x2交換機中同時傳送。具備有如此特質的光交換機架構，我們稱之為無串音(Crosstalk-free)性質。我們在這篇論文中的第一個貢獻，是去將先前Deng以及Lee[22]提出的兩步驟方法，改良成一個三步驟的方法，使得無衝突光纖佇列可以轉化成無串音光纖佇列。而某些特別的光纖佇列，包含線性壓縮器(Linear Compressor)，線性減壓器(Linear Decompressor)，無超越延遲線(non-overtaking delay line)等，可以再進一步(論文中的第四個步驟)去減少它的架構複雜度。對於這些光纖佇列，我們只需要比原來架構多一個2x2交換機，就可以建構出無串音的架構。
我們在這篇論文的第二個貢獻，是對於原本的無衝突光纖佇列，以及改良過的無串音光纖佇列，去提供了最差訊號雜訊比(Signal-to-noise ratio)的分析。除此之外，我們也推導出了這兩個最差訊號雜訊比的公式。這些公式顯示出，在無串音的架構下，最差的訊號雜訊比擁有相當大的改良。另外，我們也提出了許多正常狀況下的實驗，以驗證我們先前的推論。

There are several recent advances in the constructions of conflict-free optical queues using optical Switches and fiber Delay Lines (SDL). Many of these conflict-free optical
queues are constructed by 2x2 switches and thus suffer from the notorious crosstalk problem. To alleviate the crosstalk problem,it is suggested in the literature that one should avoid routing two packets to the same 2x2 switch at the same time. A construction with such a property is called crosstalk-free. Our first contribution of this thesis is to extend the two-step method by Deng and Lee[22] to a three-step method that converts a conflict-free SDL element into a crosstalk-free SDL element. For certain optical queues, including linear compressors, linear decompressors, and non-overtaking delay lines, an additional step (the fourth step in our thesis) can be taken to further reduce the construction complexity. For such optical queues, one only needs 1 more 2x2 switch than the original construction.
Our second contribution of this thesis is to provide worst case analysis of the signal-to-noise ratio (SNR) in both the original conflict-free SDL element and the converted crosstalk-free SDL element. Closed-form expressions for the worst case SNRs in both SDL elements are obtained. These expressions show that the gain of the worst case SNR in the converted crosstalk-free SDL element is quite substantial. Various computer simulations for the average case are also preformed to further verify our finding in the worst case.

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