由於光分碼多工系統(optical code-division multiple-access, OCDMA)在區域網路安全效能表現提高了用戶訊號的保密性，已經引起相當大的關注。他提供了可存取性、強健的效能、高靈活性與高安全性特點。然而當設計實體層時，系統仍然有一些弱點，包括其容易被竊聽，因此網絡用戶具有一定的保密性變成一個重要的問題。
為了防止系統被竊聽，我們提出一個可重構的陣列波導光柵 (arrayed-waveguide gratings, AWGs)與最大長度序列碼(maximal-length sequence, M-sequence codes)為基礎的雙重變換指配碼架構在以提昇整個系統安全性。利用最大長度序列碼的循環性、週期性與正交性優勢，並使用開關調變(on-off keying, OOK)做編碼，此外再由中央控制中心根據不同的網路狀況去控制變換指配碼的速率以提升安全性。
本論文中加入光開關(optical switches, OSWs)與光纖時間延遲器(fiber delay lines, FDLs)在陣列波導光編解碼器以達到雙重變碼提升安全性效果。光開關的狀態將會決定於電位暫存器(electric shifting register)的狀態。中央控制台會命令電位暫存器來改變光開關和時間延遲狀態。不同的移控制暫存器狀態將重新配置陣列波導光的輸出，譜成不同的輸出編碼序列。而經過光纖時間延遲器之後，使用者的碼會形成一個二維碼矩陣，在解碼端，經過時間延遲還原，當指配碼更改的頻率比竊聽者可以檢測信息的速度快時，由於竊聽者不知道碼重構的機制，竊聽者因此無法解出想要的資訊，系統將成功地達到其安全性。在此篇論文中，我們主要針對系統保密性作完整的量化分析，對於碼空間與變碼的速度對於系統保密性之影響皆有詳細完整的分析，依結果顯示，我們所提出之波長時間雙重變碼加密的概念確實可以提高系統之保密性，使系統達到一定安全性效果。

Since the confidentiality performance in optical code-division multiple-access (OCDMA) network improves user signals safety, it has attracted considerable attention. OCDMA provides accessibility, robust performance, high flexibility and high security features. However designing the physical layer, the system still has a number of weaknesses, including vulnerable to eavesdropping, thus having confidentiality becomes an important issue.
To prevent the system from being tapped, we propose reconfigurable arrayed-waveguide gratings (AWGs) and the maximal-length sequence (M-sequence) codes based on double scrambling signature to enhance the system security. Using the periodic and orthogonal advantage of M-sequence code, the on-off keying modulation is use to encode. The system according to different network conditions to control the reconfigurable signature rate.
The state of optical switch and time delay will depend on shifting control register state. Central controller will monitor the network traffic in time. When detects security threats, a reconfiguring command will be sent and electrical shift register (SR) state change for controlling the optical switches and fiber delay line. Different states will cause to different output coding sequence. But the user still can recover the correct code completely. By frequency change the assigned code, eavesdropper can’t detection information correctly. In the thesis we mainly make a complete quantitative analysis for the confidentiality. The impact of code space and reconfigurable rate to the confidentiality are complete analysis. By the results show that double wavelength/time reconfiguration scheme can indeed improve the system security and achieve a certain effect.

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