光分碼多重存取技術允許多個使用者同時非同步地存取網路系統，因此適合應用於區域網路中。早期的光分碼多重存取技術系統是在時域上將輸入訊號和近似正交碼序列來進行調變，但這樣所需的碼長很長，且使用者的總數受限於系統中的多重擷取干擾。因此，我們利用以頻譜振幅編碼為主之光分碼多重存取技術，運用碼的相關性搭配平衡檢測技術來消除其他使用者的多重擷取干擾，而萃取出預期使用者的信號。於本論文中，我們實現光分碼多工系統的頻域編、解碼裝置並以實驗驗證之。
我們採用液晶空間光調變器來實現頻譜振幅光分碼多重擷取系統之編、解碼器，並使用單極訊號的強度檢測器來檢測雙極訊號的相關性。在光分碼多重擷取系統中，功率頻譜是由可編程的液晶空間光調變器所編碼而成，液晶空間光調變器有效調變0至π相位的改變，並加上旋轉液晶分子來改變偏振旋轉方向來提供高的消光比和低的串擾。
利用相位延遲特性的液晶空間光調變器架構光分碼多重擷取的編解碼器，並檢測匹配與不匹配瓦許代碼 (Walsh-Hadamard code) 的相關性，進行評估。實驗結果顯示，液晶空間光調變器是很好用來做光分碼多重擷取系統。

In recent years, optical code-division multiple-access (OCDMA) systems have been proposed for multiple accesses to utilize the vast bandwidth available in optical fiber. Optical CDMA systems are believed to provide asynchronous access for each user in the system, which is especially suitable for usage in local area network (LAN).
We propose a new scheme of OCDMA system by using liquid crystal (LC) Spatial Light Modulators (SLMs) with programmable bipolar codes. The key to the system performance depends on the construction of a decoder that implements a true bipolar correlation using only unipolar signals and intensity detection. In our optical access coding system, the power spectrum is coded with programmable LC-SLMs. The high polarization selectivity of these components coupled with the polarization rotation ability of liquid crystal elements makes access coding switching possible with high extinction ratio and low crosstalk.
The proposal takes advantage of phase delay characteristics of LC-SLM to construct a prototype optical CDMA coder/decoder (codec). Matched and unmatched Walsh signature codes are evaluated for correlations detection among multi-user data in the access network. This paper demonstrates that LC-SLM can be a good candidate to realize optical access network coding.

[1] M. Arumugam, “Optical fiber communication – An overview,” Pramana-J. Phys., vol. 57, no. 5-6, pp. 849-869, Nov.-Dec. 2001.
[2] M. Veeraraghavan, R. Karri, T. Moors, M. Karol, and R. Grobler, “Architectures and protocols that enable new applications on optical networks,” IEEE Commun. Mag., vol. 39, no. 3, pp. 118-127, Mar. 2001.
[3] P. Urquhart, “Component technologies for future optical networks,” IEE Proc. Optoelectron., vol. 150, no. 1, pp. 3-8, Feb. 2003.
[4] H. Kogelnik, “High-capacity optical communications: personal recollections,” IEEE J. Sel. Top. Quantum Electron, vol. 6, no. 6, pp. 1279-1286, Nov.-Dec. 2000.
[5] Y. Sasaki, “Optical fiber devices,” Transparent Optical Networks, 2000 2nd International Conference on 5-8, pp. 9-12, June 2000.
[6] K. Nakagawa and S. Shimada, “Optical amplifiers in future optical communication systems,” IEEE [see also IEEE LTS], vol. 1, no. 4, pp. 57-62, Nov. 1990.
[7] R. Giles and Li Tingye, “Optical amplifiers transform long-distance lightwave telecommunications,” Proc. IEEE., vol. 84, no. 6, pp. 870-883, June 1996.
[8] E. Abbaspour-Sani, Ruey-Shing Huang, and Chee Yee Kwok, “A novel optical accelerometer,” IEEE Electron Device Lett., vol. 16, no. 5, pp. 166-168, May 1995.
[9] M. R. Amersfoort, C.R. de Boer, F. P. G. M. van Ham, M. K. Smit, T. Demeester, J. J. G. M. van der Tol, and A. Kuntze, “Phased-array wavelength demultiplexer with flattened wavelength response,” IEEE Electron Device Lett., vol. 30, no. 4, pp. 300-302, 17 Feb. 1994.
[10] K. Okamoto, M. Ishii, Y. Hibino, Y. Ohmori, and H. Toba, “Fabrication of unequal channel spacing arrayed-waveguide grating multiplexer modules,” IEEE Electron. Lett., vol. 31, no. 17, pp. 1464-1466, 17 Aug. 1995.
[11] Wenhua Lin, Haifeng Li, Y. J. Chen, M. Dagenais, and D. Stone, “Dual-channelspacing phased-array waveguide grating multi/demultiplexers,” IEEE Photonics Technol. Lett., vol. 8, no. 11, pp. 1501-1503, Nov. 1996.
[12] R. I. Laming and M. N. Zervas, “Fibre Bragg gratings and their applications,” Integrated Optics and Optical Fibre Communications, 11th International Conference on, and 23rd European Conference on Optical Communications, vol. 4 ,no. 111 448, pp. 81-83, Sept. 1997.
[13] K. O. Hill and G. Meltz, “Fiber Bragg Grating Technology Fundamentals and Overview,” IEEE J. Lightwave Technol., vol. 15, no. 8, pp. 1263-1276, Aug. 1997.
[14] T. Erdogan, “Fiber Grating Spectra,” IEEE J. Lightwave Technol., vol. 15, no. 8, pp. 1277-1294, Aug. 1997.
[15] V. Mizrahi, S. Alexander, J. Berthold, S. Chaddick, and W. Jones, “The Future of WDM Systems,” Integrated Optics and Optical Fibre Communications, the 11th International Conference on, and the 23rd European Conference on Optical Communications, vol. 1, no. 448, pp. 137-141, Sep.1997.
[16] J. Kani, M. Teshima, K. Akimoto, N. Takachio, H. Suzuki, K. Iwatsuki, and M. Ishii, “A WDM-based optical access network for wide-area gigabit access services,” IEEE Commun. Mag., vol. 41, no. 2, pp. S43-S48, Feb. 2003.
[17] R. Dixon, “Why spread spectrum?,” IEEE Communications Soc. Mag., vol. 13, pp. 21-25, July 1975.
[18] R. Scholtz, “The spread spectrum concept,” IEEE Trans. on Communications, vol. 25, no. 8, pp. 748-755, Aug. 1977.
[19] N. Karafolas and D. Uttamchandani, “Optical fiber code division multiple access networks: a review,” Optical Fiber Technol., vol. 2, no. 17, pp. 149-168, 1996.
[20] P. Prucnal, M. Santoro and T. Fan, “Spread spectrum fiber optic local area network using optical processing,” IEEE Network, vol. 4, no. 5, pp. 547-554, May 1986.
[21] W. C. Kwong, P. Perrier and P. R. Prucnal, “Performance comparison of asynchronous and synchronous code-division multiple-access techniques for fiber-optic local area networks,” IEEE Transactions on Communications, vol. 39, no. 11, pp. 1625-1634, Nov. 1991.
[22] K. P. Jackson, G. Xaio and H. J. Shaw, “Coherent optical fiber delay-line processor,” Electron. Lett., vol. 22, no. 25, pp. 1335, 1986.
[23] M. E. Marhic, “Trends in optical CDMA, in Multigigabit Fiber Communications,” SPIE Proceedings vol. 1787, pp.80-97, 1992.
[24] D. D. Sampson and D. A. Jackson, “Spread spectrum optical fiber network based on pulsed coherent correlation,” Electron. Lett., vol. 26, no. 19, pp. 1550-1552, Sept. 1990.
[25] R. A. Griffin, D. D. Sampson, and D. A. Jackson, “Optical phase coding for code division multiple access,” IEEE Photon. Technol. Lett., vol. 4, no. 12, pp. 1401-1404, Dec. 1992.
[26] D. Sampson, R. A. Griffin, and D. A. Jackson, “Photonic CDMA by coherent matched filtering using time-addressed coding in optical ladder networks,” IEEE J. Lightwave Technol., vol. 12, no. 11, pp. 2001-2010, Nov. 1994.
[27] J. Enriguz-Gabeiras, J. Camany, and R. Fernandez de Caleya, “Effect of nonideal and fiber parameters on the performance of an all optical coherent code division multiple access,” Proceedings of EFOC/LAN’92, pp. 146-151, June 1992.
[28] M. Brandt-Pearce and B. Aazhang, “Multiuser detection for optical code division multiple access systems,” IEEE Transactions on Communications, vol. 42, no. 2, pp.1801-1810, Feb./Mar./Apr. 1994.
[29] J.A. Salehi, A.M. Weiner, and J.P. Heritage, “Coherent ultrashort light pulse code-division multiple-access communication systems,” J. Lightwave Technol., vol. 8, no. 3, pp. 478-491, Mar. 1990.
[30] D. Zaccarin and M. Kavehrad, “An optical CDMA system based on spectral encoding of LED,” IEEE Photon. Technol. Letter, vol. 5, no. 4, pp. 479-482, 1993.
[31] Steve A. Serati and Kipp A. Bauchert, “Analog spatial light modulators advances and applications,” Spatial light modulators, Proc. SPIE, vol. 3292, 1998.
[32] K.M. Johnson, D.J. McKnight and I. Underwood, "Smart spatial light modulators using liquid crystals on silicon," J. Quant. Elec., vol. 29(2), pp. 699-714, 1993.
[33] L. Nguyen, T. Dennis, B. Aazhang, and J. F. Young, “Experimental demonstration of bipolar codes for optical spectral amplitude CDMA communication,” J. Lightwave Tech., vol. 15, p.1647, 1997.
[34] Xiao-Wei Xia, Teresa K. Ewing, Steven A. Serati, Yijing Fu, Rong Zhou, John A. Neff, and Frank S. Barnes, “Demonstration of reconfigurable O-CDMA using liquid crystal modulators,” Proc. of SPIE Active and passive optical components for WDM communications III, vol. 5246, pp. 95-102, Aug. 2003.
[35] Yijing Fu, Frank Barnes, Teresa K. Ewing, Steven A. Serati, Xiao-Wei Xia “Liquid crystal modulated optical CDMA in a fiber-based testbed,” Proc. SPIE, Active and Passive Optical Components for WDM Communications IV, vol. 5595, pp. 302-309, Oct. 2004.
[36] V. Morozov, J. Neff, and H. Zhou, “Signal and noise analysis in free-space interconnects,” J. Opt. Soc. Am. A, vol. 14, p. 859, 1997.
[37] Marc M. Wefers and Keith A. Nelson, “Space-Time Profiles of Shaped Ultrafast Optical Waveforms,” IEEE J. of Quantum Electronics, vol. 32, p. 161, Jan. 1996.
[38] Hsu-Chih Cheng, Chung-Hao Wu, Chao-Chin Yang, and Yao-Tang Chang, “Wavelength Division Multiplexing/Spectral Amplitude Coding Applications in Fiber Vibration Sensor Systems,” IEEE Sensors Journal, vol. 11, no. 10, Oct. 2011.