陣列波導光柵(AWG)所建構的編解、碼器已被廣泛運用於被動式光纖到府(FTTH)網路。本論文首先提出展時與群組跳頻並內嵌入最大長度序列碼(Time-spreading/wavelength-group-hopping embedded M-sequence code)以增加使用者個數(Cardinality)與信號雜訊比等系統效能。更進一步，探討變換指配序碼(Signature Address Codeword)的機制演算法以強化系統的私密性(Confidentiality)。
為了增加使用者個數，我們運用陣列波導光柵本身既有的循環(cyclic)及自由頻譜(Free Spectral Range, FSR)區間之特性，可將寬頻光源分割成不同波長群組。其中令每一個群組作為一跳頻細元(hopping chip)。該群組跳頻方式係採用傳統的變異質數碼型(modified prime code pattern)，並將該群組內嵌入最大長度序碼型(M-sequence code pattern)以建構出一套新穎的二維光碼。再者，為了簡化陣列波導光柵使用數目暨降低最大長度序碼型上既有波長碰撞(Inherent Wavelength Collision)問題，我們選用高/低密度陣列波導光柵(Fine/Coarse AWG)與延遲線(delay line)，結合光交連元件(Optical Cross Connect, OXC)以選用不同的光輸出路徑。因此其使用者序碼指配與變換機制更具靈活性。再者，我們定義私密度的指標(degree of confidentiality, DOC)來進行私密性的定量分析。相較於傳統原始與變異性質數跳頻(prime-hop/modified prime-hop code, PHC/MPHC)二維碼，結果顯示出本架構具有較多的使用者、較佳信號雜訊比與私密性。
重要的是，為強化系統的私密性，本論文在假設竊聽者使用低成本的能量檢測器對於所欲偵知的使用者進行暴力猜測法(brute-force attacking strategy)攻擊下探討光頻二維碼變換的機制與時機。我們提出結合偵測各分佈於傳輸通道之波長的平衡度(the degree of weighted load balance)指標的機制，與推估的系統預期警告時間(anticipative warning time)以實現光頻碼變換的時機，以確保高速被動式光纖到府上安全的通訊環境。

The array waveguide grating based (AWG-based) encoder/decoder (codec) had configured over Fiber-to-the-Home (FTTH) network. In order to enhance the user cardinality as well as the confidentiality and signal-to-noise ratio (SNR) of system, the time-spreading/wavelength-group-hopping embedded M-sequence code (i.e., called TS/WGH embedded M-sequence) is constructed. Moreover, the changing signature address codeword algorithm is also performed to thwart network attacks by eavesdroppers.
First, in order to increase the user’s cardinality, we exploited the inherent cyclic and periodic free-spectral-range (FSR) properties of AWG routers, and the total number of available wavelengths is partitioned into the different FSR-hopping chip that is constructed as the modified prime code pattern and embedded M-sequence code pattern.
Secondly, in order to decrease the number of AWG routers and improve the inherent wavelength collision resulting from M-sequence code pattern, we employ fine/coarse AWG routers, optical delay line and integrate with optical cross connect (OXC) to route variable lightpaths. Hence, the assignment of signature address codeword and changing codeword mechanism is more flexibility and easy to implement.
Also, the quantitative analyses of network confidentiality are performed by assessing the attained degree of confidentiality (DOC). Compared to conventional prime-hop code (PHC) and modified prime-hop code (MPHC), the result reveals that the multiple-access interference (MAI) and bit error rate (BER) of proposed scheme is decreased and the confidentiality is increased.
Importantly, in order to enhance the confidentiality, it is assumed that the eavesdropper employs a simple low-cost energy detector to sense the presence of energy in a particular bit interval and then applies a brute-force searching algorithm to attack the targeted user. In proposed scheme, the timing of changing codeword algorithm is investigated and evaluated based on the integrations of the anticipative-warning-time policy and the degree of weighted load balance in each channel.

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