在傳統之基於頻域振幅編碼的多重協定標籤交換網路中，會分配光學碼給網路中的傳送節點，並於入口節點處將路徑上的標籤資訊嵌入使用者的封包位元中。相較於傳統的多重協定標籤交換網路，此架構節省了查找表中標籤的使用數目，也簡化了封包在傳送節點上標籤辨認及轉送的機制。然而在未來的光網路中，隨著使用者以及流量不斷地快速增長，會期望光網路能夠支援更大量的使用者。為此，本論文提出了多重協定標籤交換網路中之標籤重用架構。
標籤重用(Label Reuse)的架構，適合應用於多重協定標籤交換(Multi-Protocol Label Switching, MPLS)網路中。藉由在不同的封包交換路徑相互獨立的節點上重複使用標籤，以減少使用者封包位元裡的隱含式標籤堆疊(Label Stacking)中光學標籤碼的堆疊數量。在此架構下，由於標籤被重複使用，原來有限的可使用標籤數目能被節省，相較於原先之架構，可支援的使用者數量會有顯著的增加。另一方面，也使得標籤堆疊中光學碼的堆疊數量減少，因此標籤堆疊中光學碼彼此間的相位雜訊(Phase Intensity Induced Noise, PIIN)干擾也能降低。對於封包標籤的實現方式，我們選用頻域振幅編碼(Spectral Amplitude Coding, SAC)，除了簡化網路節點中，標籤產生及辨認機制之過程，也由於碼向量之間保有正交性，因此與標籤堆疊架構相容，在封包透過節點的傳送過程中，能省略重覆移除及新增標籤之操作，加快封包傳送的速度。

In a multi-protocol label switching (MPLS) network based on optical code division multiplexing (OCDM), each core switching node is assign with one code sequence with N chips for each specific input/output pair. With optical code division multiplexing, it creates a new way to utilize optical codes as optical labels. In this method, logic operations corresponded a look-up table is avoided, which is the toughest challenge for optical processing. Instead, it only needs to check the label in the core node with the function of optical correlation.
As the users and Internet traffic continue to grow rapidly, it is expected that optical networks will support a larger number of users in the future. However, there is a scalability problem that the more the number of core nodes exists, the more code sequences are needed. To solve this critical problem, we consider a situation that can reuse label in order to save the number of utilized labels. Under this structure, there is a significant increase in the number of users that can be supported compared to the original ones. In this thesis, we compare the relationship of the number of utilized labels and supported LSPs (label switching paths) in both situations with and without reusing labels. We also discuss the issue of cost efficiency and bandwidth efficiency. Further, the discussion of BER performance is also included.

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