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，因為它可在一個具bursty traffic的環境下提供高的統計多工增益。早期的非同調光分碼多工系統在時域上使用類正交序碼對信號編碼，但這些碼不僅長度很長，而且多重擷取干擾(multiple access interference)限制了系統的同時使用者數。因此有人提出頻域振幅編碼(spectral-amplitude-coding)光分碼多工系統來解決多重擷取干擾的問題。在這本論文中我們首先回顧了一維和二維光分碼多工系統的演進情形，然後我們以實驗驗證了應用於此種光分碼多工系統的布雷格光纖光柵(fiber Bragg gratings)編/解碼器，並提出了一個補償架構來消除由布雷格光柵的非理想頻譜特性所導致的干擾。一個不受光柵非理想頻譜特性影響之新式布雷格光柵編/解碼器也被提出。但是當系統所提供的使用者數目變多時，每個使用者的碼句將變長，以致於布雷格光柵編/解碼器必須有更多單一波長的布雷格光柵串接。這將導致更多的插入損耗，也使編/解碼器的物理尺寸變得不切實際。除此以外，有限的寬頻光源頻寬也限制了系統所能提供的所有使用者數目。

我們結合了光柵路由器的循環特性和序碼的特性，提出了二種以陣列波導光柵路由器(arrayed-waveguide grating)為基礎的頻域振幅編碼光分碼多重系統。第一個系統由於使用了最大長度序碼的循環特性，因此所提出的編/解碼器對可同時編/解多個最大長度序碼，並且多重擷取干擾仍可在解碼器被消除。由於在網路中所有的使用者可以使用單個編/解碼對，整個系統於是變得小巧且簡單。第二個系統利用了Walsh-Hadamard碼與其互補碼的關係，只要使用一個在其輸出埠放置鏡子的光柵路由器，即可產生對應於使用者訊息位元之互補碼句的頻譜，並且每個使用者在完成頻域的互補編碼與解碼時各只需一個光柵路由器。這兩個結構縮小了編/解碼器的物理尺寸，也沒有上述插入損耗的問題，使得系統的實現更切合實際。

為了在有限的光源頻寬之下提升系統的所有使用者數目，在編解碼時同時使用頻域和空間域(二維系統)是一個不錯的方式。我們延伸先前討論的一維最大長度序碼來證實二維最大面積矩陣碼（M-matrix）可以在無多重擷取干擾的情況下運作。我們發展此矩陣碼的編解碼規則，使得解碼器可在理論上完全拒絕其他使用者的干擾而萃取出預期使用者的信號。此系統可用廉價的寬頻光源和光纖光柵裝置來實現，並且編解碼器的物理尺寸也比一維系統小。而在頻域振幅編碼光分碼多重擷取系統中影響系統效能極大的光拍差(Optical beat interference)雜訊也可在此系統中得到改善，但由於這種碼在解碼時到達光檢測器的功率較大，所產生的光拍差雜訊仍然嚴重。

我們也提出了兩種不同的方法來降低二維碼系統中光拍差雜訊的大小。第一種方式是將所有干擾者碼句中相同波長的成分盡可能分散在不同的光檢測器。我們提出了改良自最大面積矩陣碼的二維碼家族-變更排列最大面積矩陣碼(Permuted M-matrix) ，其頻域編解碼器乃是應用前面提出之一維光柵路由器編碼器的結構，搭配光分裂器而成。第二種方式是使用具低相關值的序碼來作為二維碼的頻域或空域碼句。我們改良了有名的修改質數碼(modified prime codes)作為頻域簽章序碼，搭配最大長度序碼作為空域簽章序碼而提出了一個Prime/M matrix二維碼。這兩個二維碼系統不僅維持了最大面積矩陣碼系統的優點，而且由於在光檢測器所產生的光拍差雜訊比最大面積矩陣碼小，所以系統允許的同時使用者數也比較多，提升了光分碼多工系統的效能與容量。

Optical code division multiple-access (OCDMA) offers high statistical multiplexing gain in a bursty traffic environment and is thought to be a more suitable solution in local-area network. Early incoherent optical CDMA systems used pseudo-orthogonal sequences to encode signals in the time domain, but the codes were long and multiple access interference (MAI) limited the number of simultaneous users. Thus, spectral-amplitude-coding (SAC) optical CDMA systems were proposed to eliminate the influence of MAI.

In this dissertation, the evolution of one and two-dimensional OCDMA system from radio CDMA system are reviewed, then encoder/decoder based on fiber Bragg gratings (FBG) is experimentally demonstrated. One compensation scheme is proposed to eliminate the interference arising from the non-ideal filter response of FBG, and one new FBG-based encoder/decoder pair not suffered from non-ideal filter response is presented and analyzed. However, when the number of total users supported by the system becomes large, the lengths of each user’s signature sequences grow longer and the FBG encoders/decoders should have more individual FBGs cascaded. This introduces more insertion losses and the physical sizes of coding devices become impractical. In addition, the finite bandwidths of broadband sources also limit the number of total users supported by the system.

By utilizing the cyclic property of arrayed-waveguide grating (AWG) router and the characteristic property of adopted codes, two SAC-OCDMA systems based on AWG routers are proposed. The first system utilizes the cyclic property of M-sequence codes, and the proposed codec pair can encode/decode multiple codewords of M-sequence code while retaining the ability for MAI cancellation. The total system becomes more compact and simple because all users in the network can use a single encoder/decoder pair. By adopting the relation between complementary Walsh-Hadamard (CWH) codes and the associated complement codes, one mirrored AWG router is used to produce either amplitude spectrum of complementary codewords in the second system, and each user requires only one AWG router to implement spectral complementary encoding and decoding, respectively. These two configurations reduce the physical size of the coder, making the implementation of systems more realizable.

To increase the number of total users in the system under the limit of finite source bandwidth, the users’ information can be encoded and decoded in both the spectral and spatial domain. We extend one-dimensional (1-D) M-sequence codes to demonstrate that the two-dimensional (2-D) maximal-area matrices (M-matrices) codes can be operated without any multiple-access interference. The associated decoding scheme is developed to make the decoder reject other users’ interferences and extract the information of desired user. This system can be implemented with cheap broadband sources and FBGs, and the physical size of encoder/decoder is smaller as compared to that for 1-D system. The performance degradation due to beat noise in 1-D M-sequences coding can be improved with the 2-D M-matrices decoding architecture However, the power that arrives at the photo-diodes during the decoding process is relatively large, thus the beat noise arising in the photo-diodes is still serious.

Two different methods are proposed to suppress the beat noise in the 2-D systems. The first method is to disperse the power of the same wavelength contributed by all interfering codewords to distinct photo-diodes of the decoder. We propose the modified version of the M-matrix code, so called Permuted M-matrix, whose spectral encoder/decoder is derived from the 1-D AWG router-based encoder proposed. The second method is to use sequences with low cross correlation as the spectral or spatial signature sequences in the 2D codeword. After modifying the well-known modified prime codes, one new 2-D Prime/M-matrix code family is proposed by utilizing the resulting 1-D codes as the spectral signature sequences. Both schemes not only retain the advantage of the M-matrix, but also improve the performance degradation due to the beat noise in the 2-D system. Thus OCDMA systems with larger capacity are achieved and a larger number of active users are allowed to access simultaneously in the system.

[1]. R.L. Pickholtz, D.L. Schilling, and L.B. Milstein, “Theory of spread-spectrum communications - a tutorial,” IEEE Transactions on Communications, vol. Com-30, pp. 855-884, no.5, May 1982.
[2]. 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.
[3]. D.V. Sarwate, and M.B. Pursley, "Crosscorrelation Properties of Pseudorandom and Related Sequences," Proceedings of the IEEE, vol. 68, no. 5, pp. 593-619, May 1980.
[4]. E.H. Dinan, and B. Jabbari, “Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks”, IEEE Communication Magazine, p.p. 48-54, Sep. 1998.
[5]. R. Gold, “Optimal binary sequences for spread spectrum multiplexing,” IEEE Trans. Inform. Theory, vol. IT-13, pp. 619 – 621, Oct. 1967.
[6]. T. Kasami, "Weight Distribution Formula for Some Class of Cyclic Codes," Coordinated Science Lab., Univ. IL, Urbana. Tech. Rep., R-285, Apr. 1966.
[7]. TIA/EIA Interim Standard-95, "Mobile Station-Base Station Compatibility Standard for Dual-Mode Wideband Spread Spectrum Cellular System," July 1993.
[8]. K.G. Beauchamp. Walsh Functions and their Applications. London: Acadamic Press, 1975.
[9]. H.H. Chen, J.F. Yeh, and N. Suehiro, “A multicarrier CDMA architecture based on orthogonal complementary codes for new generations of wideband wireless communications,” IEEE Communications Magazine, vol. 39, Issue 10, pp. 126-135, Oct 2001.
[10]. C.F. Lam, “To Spread or Not to Spread: The Myths of Optical CDMA,” IEEE LEOS 2000 Annual Mtg., vol. 2, pp. 810–811, Nov. 2000.
[11]. L. Tancevski, and L.A. Rusch, "Impact of the beat noise on the performance of 2-D optical CDMA systems," IEEE Comm. Lett., vol. 4, pp. 264 – 266, Aug. 2000.
[12]. A. Stok, and E.H. Sargent,”Lighting the local area: optical code-division multiple access and quality of service provisioning” IEEE Network, vol. 14, no. 6, pp.42 –46, Nov.-Dec. 2000.
[13]. Y.G. Wen, Y. Zhang, and L.K. Chen, “On Architecture and Limitation of Optical Multiprotocol Label Switching (MPLS) Networks Using Optical-Orthogonal-Code (OOC)/Wavelength Label,” Optical Fiber Technology, vol. 8, no. 1, pp. 43-70, Jan. 2002.
[14]. 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.
[15]. N. Karafolas, and D. Uttamchandani, “Optical Fiber code Division Multiple Access Networks: A Review,” Optical Fiber Technology, vol. 2, no. 2, pp. 149-168, April 1996.
[16]. T. O’Farrell and S. Lohmann, “Performance analysis of an optical correlator receiver for SIK DS-CDMA communications systems,” Electron. Lett., vol. 30, no. 1, pp. 63-65, Jan. 1994.
[17]. J. Salehi, “Code division multiple access techniques in optical fiber net-works. I. Fundamental principles,” IEEE Trans. Commun, vol. 37, no. 8, pp. 834–842, Aug. 1989.
[18]. P. Prucnal, M. Santoro, and T. Fan, “Spread spectrum fiber optic local area network using optical processing,” IEEE/OSA J. Lightwave Technol., vol. LT-4, no. 5, pp. 547-554, May, 1986.
[19]. K. Kitayama, “Novel spatial spread spectrum based fiber optic CDMA networks for image transmission,” IEEE J. Select. Area Commun., vol. 12, pp. 762-772, May 1994.
[20]. W.C. Kwong and G.C. Yang, “Image transmission in Multicore-Fiber Code-Division Multiple-Access Network,” IEEE Commun. Lett., vol. 2, no. 10, pp.285-87, Oct. 1998.
[21] L. Tancevski, I. Andonovic, M. Tur and J. Budin, "Hybrid wavelength hopping/time spreading code division multiple access systems", IEE Proc. Optoelectronics, Vol. 143, No. 3, pp161-166, June 1996.
[22]. G..C. Yang, and W.C. Kwong, “Performance Comparison of Multiwavelemgth CDMA and WDMA + CDMA for Fiber-Optic Networks,” IEEE Trans. Commun., vol. 45, no. 11, pp. 1426-34, Nov. 1997.
[23]. A. Shaar, and P. Davies, “Prime sequences: Quasi-optical sequences for OR channel code division multiplexing,” Electron. Lett., vol. 19, no. 21, pp. 888-889, Oct. 1983.
[24]. D. Zaccarin, and M. Kavehrad, “An optical CDMA system based on spectral encoding of LED,” IEEE Photon. Technol. Lett., vol. 4, no. 4, pp. 479-482, April 1993.
[25]. M. Kavehrad, and D. Zaccarin, “Optical Code-Division-Multiplexed Systems Based on Spectral Encoding of Noncoherent Sources,” IEEE J. Lightwave Technol., vol. 13, no. 3, pp. 534-545, March 1995.
[26]. 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.
[27]. 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,” IEEE J. Lightwave Technol., vol. 19, no. 9, pp. 1274-1281, Sept. 2001.
[28]. Z. Wei, and H. Ghafouri-Shiraz, “Proposal of a novel code for spectral amplitude-coding optical CDMA systems,” IEEE Photon. Technol. Lett., vol. 14, pp. 414–416, Mar. 2002.
[29]. I.B. Djordjevic, and B. Vasic, “Novel Combinatorial Constructions of Optical Orthogonal Codes for Incoherent ptical CDMA Systems,” IEEE J. Lightwave Technol., vol. 21, no. 9, pp. 1869-1875, Sep. 2001.
[30]. 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.
[31]. H. Fathallah, L.A. Rusch, and S. LaRochelle, “Passive optical fast frequency-hop CDMA communications system,” IEEE J. Lightwave Technol., vol. 17, no. 3, pp. 397-405, March 1999.
[32]. 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 Electronics, vol. 34, no.11, pp. 2117-2129, Nov. 1998.
[33]. H. Geiger, A. Fu, P. Petropoulos, M. Ibsen, D.J. Richardson, and R.I. Laming, “Demonstration of a Simple CDMA Transmitter and Receiver using Sampled Fiber Gratings” Optical Communication, 1998. 24th European Conference on Volume: 1, vol.1, pp. 337-338, Sept. 1998.
[34]. A. Grunnet-Jepsen, A.E. Johnson, E.S. Maniloff, T.W. Mossberg, M.J. Munroe, and J.N. Sweetser, “Demonstration of all-fiber sparse lightwave CDMA based on temporal phase encoding,” IEEE Photon. Technol. Lett., vol. 11, pp. 1283–1285, Oct. 1999.
[35]. P.C.Teh, P. Petropoulos, M. Ibsen, and D.J. Richardson, “Phase encoding and decoding of short pulses at 10 Gb/s using superstructure fibre Bragg gratings,” IEEE Photon. Technol. Lett., vol. 13, no. 2, pp. 154-156, Feb. 2001.
[36]. D.B. Hunter and R.A. Minasian, “Programmable high-speed optical code recognition using fibre Bragg gratings arrays,” Electron. Lett., vol. 35, no. 5, pp. 412-414, March 1999.
[37]. K. Yu, and N. Park, “Design of new family of two-dimensional wavelength-time spreading codes for optical code division multiple access networks,” Electron. Lett., vol. 35, no. 10, pp. 830-831, May 1999.
[38]. N. Wada, H. Sotobayashi, and K. Kitayama, “2.5Gbits/s time-spread / wavelength- hop optical code division multiplexing using fibre Bragg grating with supercontinum light source,” Electron. Lett., vol. 36, no. 9, pp. 815-817, April 2000.
[39]. L.R. Chen, and P.W.E. Smith, “Demonstration of incoherent wavelength-encoding / time-spreading optical CDMA using chirped moire gratings,” IEEE Photon. Technol. Lett., vol. 12, no. 9, pp. 1281-1283, Sept. 2000.
[40]. R.A. Griffin, D.D. Sampson, and D.A. Jackson, “Coherence Coding for Photonic Code-Division Multiple Access Networks,” IEEE J. Lightwave Technol., vol. 13, no. 9, pp. 1826-1837, Sept. 1995.
[41]. A. Grunnet-Jepsen, , A. Johnson, E. Maniloff, T. Mossberg, M. Munroe, and J. Sweetser, “Spectral phase encoding and decoding using fiber Bragg gratings,” International Conference on Integrated Optics and Optical Fiber Communication, OFC/IOOC’99, Technical Digest PD33/1-PD33/3, pp. 21-26, Feb. 1999.
[42]. J.F. Huang and 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, Sep. 2000.
[43]. G.A. Magel, G.D. Landry, R.J. Baca, D.A. Harper, and C.A. Spillers, “Transmission of eight channels × 622 Mb/s and 15 channels × 155 Mb/s using spectral encoded optical CDMA”, Electron. Lett., vol. 37, pp. 1307-1308, Oct. 2001.
[44]. C.C. Yang, and J.F. Huang, “Two-Dimensional M-Matrices Coding in Spatial/Frequency Optical CDMA Networks,” IEEE Photon. Technol. Lett., pp. 168-170, vol. 15, no.1, Jan. 2003.
[45]. T. Erdogan, “Fiber grating spectra,” IEEE J. Lightwave Technol., vol.15, no. 8, pp.1277-1294, Aug. 1997.
[46]. C.E. Lee, and H.F. Taylor, “Intensity noise in long-wavelength superluminescent sources,” IEEE J. Quantum Electron., vol. 27, pp. 1171–1174, May 1991.
[47]. P.R. Morkel, R.I. Laming, and D.N. Payne, “Noise characteristics of high-power doped-fiber superluminescent sources,” Electron. Lett., vol. 26, no. 2, pp. 96–98, Jan. 1990.
[48]. P.F. Wysocki, M.J.F. Digonnet, and B.Y. Kim, “Spectral Characteristics of High-Power 1.5 mm Broad-Band Superluminscent Fiber Sources,” IEEE Photonics Techn. Lettr., vol. 2, no.3, pp. 178-180, March 1990.
[49]. E.D.J. Smith, R.J. Blaikie, and D.P. Taylor, “Performance enhancement of spectral-amplitude-coding optical CDMA using pulse-position modulation,” IEEE Trans. Commun., vol. 46, pp. 1176-1185, Sept. 1998.
[50]. B. Moslehi, “Noise power spectra of optical two-beam interferometers induced by the laser phase noise,” J. Lightwave Technol., vol. 4, no. 11, pp. 1704–1710, Nov. 1986.
[51]. H. Takahashi, K. Oda, H. Toda, and Y. Inoue, “Transmission characteristics of arrayed waveguide N×N wavelength multiplexer,” J. Lightwave Technol., vol. 13, pp. 447-455, March 1995.
[52]. S. Kim, “Cyclic optical encoders/decoders for compact optical CDMA network,” IEEE Photon. Technol. Lett., vol. 12, pp. 428-430, Apr. 2000.
[53]. K. Yu, J. Shin, and N. Park, “Wavelength-Time spreading optical CDMA system using wavelength multiplexers and mirrored fiber delay lines,” IEEE Photon. Technol. Lett., vol. 12, pp. 1278–1280, Sept. 2000.
[54]. C.F. Lam, D.T.K. Tong, M.C. Wu, and E. Yablonovitch, “Experimental Demonstration of Bipolar Optical CDMA System Using a Balanced Transmitter and Complementary Spectral Encoding“, IEEE Photonics Technology Letters, Vol. 10, No. 10, pp1504-1506, Oct. 1998.
[55]. M.K. Smit, “New focusing and dispersive planar component based on an optical phase array,” Electron. Lett., vol. 24, pp. 385-386, March 1988.
[56]. H. Takahashi, K. Oda, and H. Toba, “Impact of crosstalk in an arrayed-waveguide multiplexer on NxN optical interconnection,” J. Lightwave Technol., vol. 9, pp. 1285- 1287, Sept. 1997.
[57]. B. Glance, I.P. Kaminow, and R.W. Wilson, “Applications of the integrated waveguide grating router,” J. Lightwave Technol., vol. 12, no. 6, pp. 957- 962, June 1994.
[58]. J. W. Goodman, Statistical Optics. New York: Wiley, 1985.
[59]. 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 Trans. Commun., pp. 1625-1634, vol. 39, no. 11, Nov. 1991.
[60]. C.J. Kuo, and H.B. Rigas, “2-D quasi m-arrays and Gold code arrays,” IEEE Trans. Inform. Theory, vol. 37, pp. 385 - 388 (1991).
[61]. J.F. Huang, C.C. Yang, and C.H. Chou, “Evaluations on a Buffering WDM Optical Packet Switch Equipped with Shared Wavelength Converters, “ Journal of Optical Communications, vol.25, no.1, pp.20-30, Feb. 2004.
[62]. J.F. Huang, and C.C. Yang, ”Broadband ATM Switching Routers Configured with Quasi-Orthogonal Optical CDMA Fiber Gratings, ” Proceedings of the 2000 National Symposium on Telecommunications, pp. 2-129 - 2-134, Chung Yuan Christian University, Chung-Li, Taiwan, Dec. 15-16, 2000.
[63]. J. Wu, and C.L. Lin, “Fiber-optic code division add-drop multiplexers,” J. Lightwave Technol., vol. 18, no. 6, pp. 819- 824, June 2000.