由於無線多媒體通訊系統快速發展之下，傳輸系統被要求必須擁有大量的頻寬來傳輸各式各樣的資料，光載無線訊號(radio-over-fiber, RoF)結合了無線與光纖的優點可用來解決頻寬不足以及高傳輸損耗的問題。近年來，光分碼多工技術(Optical Code-Division Multiple-Access, OCDMA)被視為是區域網路的最佳選擇，它有許多優點，例如:可非同步傳輸、保密性高、對網路設計較有彈性、以及在一個具擁擠的網路環境下提供高的統計多工增益。
在這篇論文中，我們提出了一組殘留填塞式二次同餘碼(RSQC codes)適用於光載無線系統與頻域振幅編碼(spectral-amplitude-coding)光分碼多工技術之混合架構，利用權重刪減的方式，可使碼空間變大、提升用戶間的保密性且擁有兩碼鍵移(two-code keying)的能力。在系統效能分析方面，我們在雜訊的部份考慮了熱雜訊(thermal noise)與相位引發強度雜訊(Phase-Induced Intensity Noise, PIIN)，並且考慮當無線訊號使用二位元相位偏移調變(binary phase shift keying, BPSK)時所造成的錯誤率(bit error rate)。藉由與原本的填塞式二次同餘碼(SQC codes)利用開關鍵移(on-off keying)做比較，從研究結果顯示當無線基地台數目少時我們所提出的殘留填塞式二次同餘碼有較好的系統效能，但是當無線基地台數目變多時原本的填塞式二次同餘碼反而有較好的系統效能，因此可根據系統的需求選擇使用我們所提出的殘留填塞式二次同餘碼或是原本的填塞式二次同餘碼。

Under the rapid development of wireless communication, the requests of higher transmission rate and larger bandwidth for personal wireless applications have increased. Radio-over-fiber (RoF) links, combined the merits of wireless with optical fiber, are designed to solve the busy traffic and high transmission loss. In recent years, optical code-division multiple-access (OCDMA) is thought to be a more suitable solution in local-area network because they offer several advantages such as asynchronous transmission, security in transmission, flexibility in network design, and can be offered even in bursty traffic.
In this study, we proposed the residue-stuffed-quadratic-congruence (RSQC) code family for the radio signal transmissions over spectral-amplitude-coding (SAC) OCDMA system. By using the residue method, these new codes can enlarge the code space, enhance the security, and have two-code keying ability. In analyzing the performance of the RoF-OCDMA system we have considered thermal noise and phase-induced intensity noise (PIIN). The bit error rate (BER) performance for RoF-OCDMA using binary phase shift keying (BPSK) is compared with the SQC code based on on-off keying. The results show that when the number of radio base stations (RBSs) is small, system performance of the RSQC codes are better than that of the SQC codes, but when the number of RBSs is large, system performance of the RSQC codes are lower than the SQC codes. Depending on the advantages and disadvantages of the two-code keying (RSQC codes) and the on-off keying (SQC codes), the suitable codes can be selected for the system.

[1]S. Komaki, K. Tsukamoto, M. Okada, and H. Harada, “Proposal of radio highway networks for future multimedia-personal wireless communications,” in Proc. ICPWC’94, pp. 204–208, Aug. 1994.
[2]T. S. Chu and M. G. Gans, “Fiber optic microcellular radio," IEEE Trans. Veh. Technol., vol. 40, pp. 599–606, 1991.
[3]C. Lim, A. Nirmalathas, M. Bakaul, P. Gamage, K.-L. Lee, Y. Yang, D. Novak, and R. Waterhouse, “Fiber-wireless networks and subsystem technologies,” J. Lightwav Technol., vol. 28, no. 4, pp. 390–405, Feb. 2010.
[4]R. Scholtz, “The spread spectrum concept,” IEEE Transactions on Communications, vol. 25, no. 8, pp. 748-755, August 1977.
[5]G.R. Cooper and R.W. Nettleton, "A Spread Spectrum Technique for High-Capacity Mobile Communications", IEEE Trans. Vehicular Tech., Vol. VT-27, no.4, pp 264-275, Nov. 1978.
[6]J. Y. Hui, “Pattern Code Modulation and Optical Decoding — A Novel Code-Division Multiplexing Technique for Multifiber Network,” IEEE J. Select. Area Commun., vol. SAC-3, no. 6, pp. 916–27, Nov. 1985.
[7]J. A. Salehi, “Code division multiple-access techniques in optical fiber networks—Part II: Systems performance analysis,” IEEE Trans. Commun., vol. 37, no. 8, pp. 834–842, Aug. 1989.
[8]D. Zaccarin and M. Kavehrad, "An optical CDMA system based on spectral encoding of LED," IEEE Photon. Technol. Lett., vol. 5, pp. 479-482, 1993.
[9]M. Kavehrad and D. Zaccarin, “Optical code-division-multiplexed systems based on spectral encoding of noncoherent sources,” J. Lightwave Technol, vol. 13, no. 3, pp. 534-545, Mar. 1995.
[10]X. Zhou, H. M. H. Shalaby, C. Lu, and T. Cheng, “Code for spectral amplitude coding optical CDMA systems,” Electron. Lett., vol. 36, pp. 728–729, Apr. 13, 2000.
[11]J.F. Huang, D.Z. Hsu, “Fiber-grating-based optical CDMA spectral coding with nearly orthogonal M-sequence codes,” IEEE Photon. Technol. Lett., vol. 12, no. 9, pp. 1252-1254, Sept. 2000.
[12]S. Kajiya, K. Tsukamoto, and S. Komaki, “Proposal of fiber-optic radio highway networks using CDMA method,” IEICE Trans. Electron., vol. E79-C, no. 1, pp. 111–117, Jan. 1996.
[13]K. Tsukamoto, T. Higashino, T. Nakanishi, and S. Komaki, “Direct optical switching code-division multiple-access system for fiber-optic radio highway networks,” J. Lightwave Technol., vol. 21, no. 12, pp. 3209-3220, Dec. 2003.
[14]B. K. Kim, S. Park, Y. Yeon, and B. W. Kim, “Radio-over-fiber system using fiber-grating-based optical CDMA with modified PN codes,” IEEE Photon. Technol. Letter, vol. 15, no. 10, pp. 1485–1487, Oct. 2003.
[15]T. Demeechai, “Noise-limited performance of spectral-amplitude-coding optical CDMA in fibre-optic radio highway networks," IEE Proc. Optoelectronics, vol. 152, no. 5, pp. 269-273, Oct. 2005.
[16]C. C. Yang, “Optical CDMA fiber radio networks using cyclic ternary sequences,” IEEE Communications Letters, Vol. 12, No. 1, pp. 41–43, January 2008.
[17]C. C. Yang, “Bi-directional optical CDMA-based fiber-radio ring networks,” IEEE Trans. Commun., vol. 57, no. 3, pp. 771–778, Mar. 2009.
[18]C. C. Yang, “Code Space Enlargement for Hybrid Fiber Radio and Baseband OCDMA PONs,” J.Lightw.Technol, vol. 29, no. 9, pp. 1394–1400, May. 2011.
[19]C. C. Yang, “Compact optical CDMA passive optical network with differentiated services,” IEEE Trans. Commun., vol. 57, no. 8, pp. 2402–2409, Aug. 2009.
[20]Z. Wei, H. M. H. Shalaby, and H. Ghafouri-Shiraz, “Modified quadratic congruence codes for fiber bragg grating based spectral-amplitude-coding optical CDMA systems,” J. Lightwave Technol., vol. 19, no. 9, pp. 1274-1281, September 2001.
[21]C. C. Yang, “Optical CDMA passive optical network using prime code with interference elimination,” IEEE Photon. Technol. Lett., vol. 7, no. 19, pp. 516-518, Apr. 2007.
[22]C. C. Yang, J. F. Huang, and S. P. Tseng, “Optical CDMA network codecs structured with M-sequence codes over waveguide-grating routers,” IEEE Photon. Technol. Lett., vol. 16, no. 2, pp. 641-643, Feb. 2004.
[23]J. F. Huang, C. C. Yang, and H. P. Tseng, “Complementary Walsh-Hadamard coded optical CDMA coder/decoders structured over arrayed-waveguide-grating routers,” Opt. Commun., vol. 229, no. 1–6, pp. 241–248, Jan. 2004.
[24]K. O. Hill and G. Meltz, “Fiber Bragg grating technology fundamentals and overview,” J. Lightwave Technol., vol. 15, pp. 1263–1276, Aug. 1997.
[25]D. K. W. Lam, and B. K. Garside, “Characterization of single-mode optical fiber filters,” Applied Optics, vol. 20, pp. 440-445, 1981.
[26]L. R. Chen, S. D. Benjamin, P.W. E. Smith, and J. E. Sipe, “Applications of ultrashort pulse propagation in Bragg gratings for wavelength division multiplexing and code division multiple access,” IEEE J. Quantum Electron., vol. 34, pp. 2117–2129, Nov. 1998.
[27]E.D.J. Smith, R.J. Blaikie, and D.P. Taylor, “Performance enhancement of spectral-amplitude-coding optical CDMA using pulse-position modulation,” IEEE Transactions on Communications, vol. 46, pp. 1176-1185, Sept. 1998.
[28]D. E. Borth and M. B. Pursley, “Analysis of direct-sequence spread spectrum multiple-access communication over Rician fading channels,” IEEE Trans. Commun., vol. COM-27, pp. 1566–1577, Oct. 1979.
[29]B. J. Koshy and P. M. Shankar, “Spread-spectrum techniques for fiber-fed microcellular networks,” IEEE Trans. Veh. Technol., vol. 48, no. 3, pp. 847–857, May 1999.
[30]W. Huang, M. Nakagawa, Nonlinear effect of direct-sequence CDMA in optical transmission, IEICE Trans. Commun., vol. E78-B, no. 5, pp.702–708, May 1995.
[31]Huang, J.F., Yen, C.T., Li, T.Y., ‘Nonlinearity effect of electro-optical modulator response in double spread CDMA radio-over-fiber transmissions’, Opt. Fiber Technol., vol. 14, no. 3, pp. 247–258, Feb. 2008.