應用混合延伸式最大長度序列碼及完美相差碼於二維光分碼多工被動光網路

光分碼多工系統有著高傳輸速率、高安全性以及非同步傳輸等優點，被視為相當適合建構被動光網路。但是由於光訊號功率無負值，使得在傳統的時域編碼光分碼多工系統中，編碼之間的交互相關係數過大，使得多重使用者干擾嚴重的影響了系統效能。而在頻域上編碼的頻域振幅編碼光分碼多工系統越來越受重視，由於編碼是在頻域上展開，可避免了在時域上編碼所必須使用的高速電子元件所造成的系統複雜度；另一方面，多種具有固定大小的交互相關係數的編碼的提出，使得多重使用者干擾可在接收端完全消除。但是由於使用的寬頻光源為一非同調光源，使得系統會產生相位引起的強度雜訊，使得系統效能被嚴重的影響。另一方面，由於編碼是在頻域上展開，使得編碼的長度受限於傳輸端光源的頻寬。為了突破使用者上限的限制，許多二維編碼的系統相繼提出，其中之一為同時使用多條光纖傳輸的頻域及空間編碼系統。頻域及空間編碼系統保留了頻域振幅編碼系統的優點，同時大幅的增進了使用者上線的數量。但是同樣的，二維頻域及空間編碼系統也被相位引起的強度雜訊嚴重的影響。在本論文中，我們提出了一個新的二維頻域及空間光分碼多工被動光網路；這個系統使用了一種新的編碼，稱為混合延伸式最大長度序列碼及完美相差碼。由於此編碼的一些特性，使得使用此編碼建構的被動光網路的複雜度比起使用其他編碼大幅下降。另一方面，根據此編碼的交互相關特性，使得相位引起的強度雜訊可以有效的抑制。效能分析的結果顯示出，使用混合延伸式最大長度序列碼及完美相差碼的系統在同樣的錯誤率需求下，可以提供比使用其他編碼的系統更多的使用者數及更高的傳輸速率。

關鍵字

光分碼多工；被動光網路；頻域振幅編碼

並列摘要

Optical code division multi-access (OCDMA) system is regarded as a good solution of passive optical network (PON), because it provides users to access the network asynchronously with high transmission rate and high security. The performance of OCDMA system is mainly limited by multi-user interference (MUI). Because of using intensity detection, this kind of interference is unavoidable in traditional time-spreading OCDMA systems. The spectral amplitude coding (SAC) OCDMA systems were proposed to eliminate the MUI. When the codes with fixed cross-correlation is used, the MUI could completely eliminates at the receiver. However, the incoherent broadband light source is used in SAC-OCDMA systems, the system performance suffers from phase induced intensity noise (PIIN). Furthermore, in these systems, the code length should be made larger in order to accommodate enough simultaneous users. However, the code length is limited by finite bandwidth of light source. The two-dimensional spectral/spatial coding scheme which retains the advantages of SAC-OCDMA systems were proposed to overcome this limitation. However, it still suffers from PIIN. In this thesis, we propose hybrid extended m-sequence code (EMC) / extended perfect difference code (EPDC) codes. And we construct the corresponding OCDMA-PON. Because of some good property of hybrid EMC/EPDC codes, the complexity of the constructed OCDMA PON is reduced. Furthermore, the numerical results show that the OCDMA-PON we proposed has better performance than many other systems.

並列關鍵字

OCDMA ； PON ； SAC

參考文獻

[1] P. R. Prucnal, M. A. Santoro, and T. R. Fan, “Spread spectrum fiberoptic local area network using optical processing,” J. Lightw. Technol., vol. LT-4, no. 5, pp. 547–554, May 1986.

[2] W. C. Kwong, P. A. Perrier, and P. R. Prucnal, “Performance comparison of asynchronous and synchronous code-division multiple-access techniques for fiber-optic local area networks,” IEEE Trans. Commun., vol. 39, no. 11, pp. 1625–1634, Nov. 1991.

[3] C.-S. Weng and J. Wu, “Perfect difference codes for synchronous fiber-optic CDMA communication systems,” J. Lightw. Technol., vol. 19, no. 2, pp. 186–194, Feb. 2001.

[4] H. Fathallah, L. A. Rusch, and S. LaRochelle, “Passive optical fast frequency-hop CDMA communications system,” J. Lightw. Technol., vol. 17, no. 3, pp. 397–405, Mar. 1999.

[5] E. Inaty, H. M. H. Shalaby, and P. Fortier, “On the cutoff rates of a multiclass OFFH-CDMA system,” IEEE Trans. Commun., vol. 53, no. 2, pp. 323–334, Feb. 2005.

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應用混合延伸式最大長度序列碼及完美相差碼於二維光分碼多工被動光網路

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