此篇論文中，我們提出及研究幾個架構在布雷格光纖光柵(fiber-Bragg grating, FBG)頻域振幅(spectral-amplitude coding, SAC)光分碼多工(optical code-division multiple-access, OCDMA)網路編解碼器。頻域振幅光分碼多工網路是根據序列具有固定交互相關的虛擬正交特性來實現多重擷取干擾(multiple-access interference, MAI)的消除。經由多工編碼技術，像是Hadamard-Walsh codes或是最大長度序碼(M-sequence codes)的虛擬正交碼相關性相減被應用在所提出的頻域振幅編碼系統裏。
　　為了要降低插入損失，大部份的多重布雷格光纖光柵都是以串接的方式來建構光分碼多工網路編解碼器；然而，當使用多重布雷格光纖光柵的反射信號時，光路遊效應將存在於決策電路中。光路遊效應就是反射的布雷格波長在多重布雷格光纖光柵所行進的時間。這個效應將限制所傳的波長信號同時抵達到決策裝置。為了避免光路遊效應，我們首先利用光延遲的觀念來設計頻域振幅光分碼多工網路的編解碼器。
　　此外，寬頻光源的頻譜可能是不平坦的，因此導致其它的多重擷取干擾問題，這是因為每個使用者都擁有不同的序列碼，因而會分佈在不同波長頻譜上。我們將處理編碼頻譜細片元的平坦問題，以達到我們所要設計的細片元能量值，經由利用更多在編碼區域外的布雷格光纖光柵細片元來補償不足的編碼細片元。由於編碼區域大部分都是在半頻寬(Full Width of Half Maximum, FWHM)區域內，但在編碼區域外的頻譜仍然具有能量，因此我們能夠取得並補償能量不夠的編碼細片元。為了使用這些編碼區域外的頻譜，更多兼具彈性運用的布雷格光纖光柵是一個適當的選擇，使得我們可以濾出想要的細片元來補償能量不足的編碼細片元，也就是說，每個碼序列的元素都具有幾乎相同的能量。因此，由不平坦光源所導致的多重擷取干擾能夠被降低。
　　在第三章，布雷格光纖光柵的穿透頻譜特性被運用在建構一個無迴光器的光分碼多工網路編解碼。然而此架構中，不需要的頻譜會伴隨著編碼細片元抵達到光檢測器，導致較高的相位強度雜訊(phase-induced intensity noise, PIIN)及多重擷取干擾。一個放在光分碼多工編解碼器模組中的殘留頻譜消除器(residual-spectra eliminator, RSE)將被用來移除這些不需要的頻譜資料，因而相位強度雜訊及多重擷取干擾可以被抑制。一個簡單的實驗基於利用布雷格光纖光柵穿透頻譜特性的編解碼器搭配使用殘留頻譜消除器用來驗証抑制在光檢測器的殘留頻譜雜訊。效能分析顯示在無迴光器網路編解碼器中，使用殘留頻譜消除器，可以很有效率的在光檢測器上降低相位強度雜訊。
　　然而，實際上的布雷格光纖光柵因具有非理想的反射係數，使得在穿透端上會有些能量存在，此遺漏的能量會產生多重擷取干擾與相位強度雜訊。理想的布雷格光纖光柵是一完美方波，我們可以串接2個或更多個相同頻率但非理想的布雷格光纖光柵來近似一個完美方波。數學模擬研究中，串接不同布雷格光纖光柵數量會反應至細片元的形狀，影響至錯誤率(bit-error rate, BER)及在頻域振幅編碼光分碼多工網路使用者可以被提供的數量。此方法也可防止布雷格光纖光柵因時間老化而導致反射率降低的問題。我們用一個簡單的實驗來驗証方波的近似。此方法顯示，串接多個相同頻率的布雷格光纖光柵提供布雷格光纖光柵在使用時間上及光分碼多工系統上一個重要的改善。分析的結果顯示結合殘留頻譜消除器及串接多個布雷格光纖光柵，頻域振幅編碼光分碼多工網路可以很有效率的改善能量遺漏及相位強度雜訊的問題。

　In this thesis, several spectral-amplitude coding (SAC) optical code-division multiple- access (OCDMA) network coder/decoders (codecs) based on fiber-Bragg grating (FBG) filters are presented and investigated. The SAC-OCDMA network is according to the pseudo-orthogonality of the in-phase cross-correlation sequences to implement the multiple-access interference (MAI) cancellation. By multiple-access coding techniques, correlation subtractions of nearly orthogonal codes such as orthogonal Hadamard-Walsh codes or nearly orthogonal M-sequence codes are applied in the proposal SAC scheme.
　In order to reduce the insertion loss, the general multiple FBGs are cascaded to construct the codec for the SAC-OCDMA network; however, the round trip time effect would exist at decision circuit when one applying reflective signals of multiple FBGs. The round trip time is the time of the reflective wavelength traveling in multiple FBGs. This effect confines the transmitted wavelengths on one bit that simultaneously arrive at the decision device. To avoid the round trip time effects, we first apply the optical delay lines concept to design the codec on SAC-OCDMA network.
　Furthermore, the broadband light source might be not a flattened broadband spectrum. It causes another MAI problems, because each active user with different code sequence occupies the different distributions in the spectral domain. We will deal with the power flatness of the coded spectral chips to approach a designed chip power value by employing more FBG chips outside the coding area to compensate the insufficient chips power. Since the coding area is always in the Full Width of Half Maximum (FWHM) region, outside the coding area is still with the power and hence can be applied to compensate not enough coding chip power. To make of these outside area, more FBGs with flexible characteristic are appropriate to filter a desire power coincided with insufficient chip power, that is, for every element of code sequence owns the nearly equivalent power. Therefore, the MAI effect caused by non-flatten source can be reduced for using this process.
　In chapter 3, transmissive spectral characteristics of FBGs are applied to construct a circulator-free scheme of OCDMA network codec. The unnecessary spectra would accompany the coding chips to arrive at the photo-detectors (PDs) to induce higher phase-induced intensity noise (PIIN) and MAI. A residual-spectra eliminator (RSE) between OCDMA encoder and decoder modules is employed to remove the unnecessary spectral part of data so that the PIIN and MAI can be reduced. A simple experiment performed on the basis of transmissive spectral characteristics of FBGs together with RSE is demonstrated to verify the capability of suppressing residual-spectra noise at the PDs. Performance evaluations indicate that using RSE between network codecs can remarkably lower the PIIN effects in the receiver PDs.
　However, real FBGs have non-ideal reflection coefficients and so transmit some spectral power where there should be none, producing leakage-induced MAI and high phase-induced intensity noise (PIIN). Ideal FBGs filter perfect square profile, a spectral condition is approached in this study by cascading 2 or more same-frequency non-ideal FBGs. Mathematical simulation investigates the number of cascaded FBGs relative to level of chip shaping, to bit-error rate (BER) levels and to the number of active users that can be supported in an SAC-OCDMA network. As a second issue, it is known that FBGs degrade over time. A simple experiment is demonstrated to verify the square-like approach. It is shown that cascaded same-frequency FBGs provide significant improvement in FBG device lifetime and stability. Evaluation results show that the combination of RSE with cascaded FBGs can significantly improve the leakage and the PIIN effects for the SAC-OCDMA network.

[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, March 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-channel- spacing 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 (Conf. Publ. No.: 448), vol. 4, 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, 11th International Conference on, and 23rd European Conference on Optical Communications (Conf. Publ. No.: 448), vol. 1, no. 448, pp.137-141, Sept.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] G. Vannucci, ”Combining frequency-division and code-division multiplexing in a high-capacity optical network,” IEEE Netw., vol. 3, no. 2, pp. 21-30, March 1989.
[18] A. Stok and E.H. Sargent, “Lighting the Local Area: Optical Code-Division Multiple Access and Quality of Service Provisioning,” IEEE Netw., vol. 14, no. 6, pp. 42–46, Nov.-Dec. 2000.
[19] A. Stock and E. H. Sargent, “The Role of Optical CDMA in Access Networks,” IEEE Commun. Mag., pp. 83-87, Sept. 2002.
[20] Jagdeep Shan, “Optical CDMA”, Optics & Photonics News, pp. 42-47, April 2003.
[21] A. D. Kersey, M. A. Davis, H. J. Patrick, M. LeBlanc, K. P. Koo, C. G. Askins, M. A. Putnam, E. J. Friebele, “Fiber grating sensors,” IEEE J. Lightwave Technol., vol. 15, no. 8, pp. 1442-1463, Aug. 1997.
[22] K. O. Hill, B. Malo, F. Bilodeau, D. C. Johnson, and J. Albert, “Bragg gratings fabricated in monomode photosensitive optical fiber by UV exposure through a phase mask,” Appl. Phys. Lett., vol. 62, pp. 1035-1037, 1993.
[23] D. Z. Anderson, V. Mizrahi, T. Erdogan, and A. E. White, “Production of in-fibre gratings using a diffractive optical element,” Electron. Lett., vol. 29, pp. 566-568, 1993.
[24] S. D. Dods and R. S. Tucker, “A comparison of the homodyne crosstalk characteristics of optical add-drop multiplexers,” IEEE J. Lightwave Technol., vol. 19, no. 12, pp. 1829-1838, Dec. 2001.
[25] R. J. S. Pedersen and B. F. Jorgensen, “Impact of coherent crosstalk on usable bandwidth of a grating-MZI based OADM,” IEEE Photonics. Technol. Lett., vol. 10, no. 4, pp. 558-560, April 1998.
[26] T. Mizumoto, H. Chihara, N. Tokui, and Y. Naito, “Verification of waveguide-type optical circulator operation,” Electron. Lett., vol. 26, no. 3, pp. 199–200, Feb. 1990.
[27] H. Okayama, Y. Ozeki, and T. Kunii, “Dynamic wavelength selective add/drop node comprising tunable gratings,” Electron. Lett., vol. 33, no. 10, pp. 881–882, May 1997.
[28] Jungho Kim and Byoungho Lee, “Bidirectional Wavelength Add-Drop Multiplexer Using Multiport Optical Circulators and Fiber Bragg Gratings,” IEEE Photon. Technol. Lettr., vol. 12, no 5, pp. 561-563, May 2000.
[29] P. Prucnal, M. Santoro and Ting Fan “Spread spectrum fiber-optic local area network using optical processing,” IEEE J. Lightwave Technol., vol. 4, no. 5, pp. 547-554, May 1986.
[30] J. A. Salehi, “Code Division Multiple-Access Techniques in Optical Fiber Networks- Part I: Fundamental Principles,” IEEE Trans. Commun., vol. 37, no. 8, pp. 824-833, Aug. 1989.
[31] 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.
[32] 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.
[33] Li Bin “One-coincidence sequences with specified distance between adjacent symbols for frequency-hopping multiple access,” IEEE Trans. Commun., vol. 45, no. 4, pp. 408-410, April. 1997.
[34] L. Tancevski, I. Andonovic, M. Tur, J. Budin, “Hybrid wavelength hopping/time spreading code division multiple access systems,” IEE Proc.- Optoelectron., vol. 143, no. 3, pp. 161-166, June 1996.
[35] R. M. H. Yim, L. R. Chen, and J. Bajcsy, “Design and performance of 2-D codes for wavelength-time optical CDMA,” IEEE Photonics Technol. Lett., vol. 14, no. 5, pp. 714-716, May 2002.
[36] 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.
[37] A. Iocco, H. G. Limberger, R. P. Salathe, L. A. Everall, K. E. Chisholm, J. A. R. Williams and I. Bennion, “Bragg grating fast tunable filter for wavelength division multiplexing,” IEEE J. Lightwave Technol., vol.17, no.7, pp. 1217-1221, July 1999.
[38] L. R. Chen, “Flexible fiber Bragg grating encoder/decoder for hybrid wavelength- time optical CDMA,” IEEE Photonics Technol. Lett., vol. 13, no. 11, pp. 1233- 1235, Nov. 2001.
[39] Sheng Peng Wan and Yu Hu; “Two-dimensional optical CDMA differential system with prime/OOC codes,” IEEE Photonics Technol. Lett., vol. 13, no. 12, pp. 1373-1375, Dec. 2001.
[40] R. M. H. Yim, J. Bajcsy, and L. R. Chen, “A new family of 2-D wavelength-time codes for optical CDMA with differential detection,” IEEE Photonics Technol. Lett., vol. 15, no. 1, pp. 165-167, Jan. 2003.
[41] H. Heo, Seong-sik Min, Yong Hyub Won, Y. Yeon, Bong Kyu Kim, and Byoung Whi Kim “A new family of 2-D wavelength-time spreading code for optical code-division multiple-access system with balanced detection,” IEEE Photonics Technol. Lett., vol. 16, no. 9, pp. 2189-2191, Step. 2004.
[42] D. Zaccarin and M. Kavehrad, “An optical CDMA system based on spectral encoding of LED,” IEEE Photonics. Technol. Lett., vol. 4, no. 4, pp. 479-482, Apr. 1993.
[43]. M. Kavehrad and D. Zaccarin, “Optical code-division-multiplexed systems based on spectral encoding of noncoherent sources,” IEEE J. Lightwave Technol., vol. 8, no 3, pp. 534-545, March 1995.
[44] L. Nguyen, B. Aazhang, and J. F. Young, “All-optical CDMA with bipolar codes,” Electron. Lett., vol. 31, no. 6, pp. 469-470, Mar. 1995.
[45] L. Nguyen, T. Dennis, B. Aazhang and J. F. Young, “Optical spectral amplitude CDMA communication,” IEEE J. Lightwave Technol., vol. 15, no 9, pp. 1647-1653, Step. 1997.
[46] Zou Wei, H. Ghafouri-Shiraz and H. M. H. Shalaby, “New code families for fiber- Bragg-grating-based spectral-amplitude-coding optical CDMA systems,” IEEE Photonics. Technol. Lett., vol. 13, no. 8, pp. 890-892, Aug. 2001.
[47] Zou 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, Step. 2001.
[48] I. B. Djordjevic, B. Vasic and J. Rorison, “Design of multiweight unipolar codes for multimedia optical CDMA applications based on pairwise balanced designs,” IEEE J. Lightwave Technol., vol. 21, no 9, pp. 1850-1856, Step. 2003.
[49] I. B. Djordjevic and B. Vasic, “Novel combinatorial constructions of optical orthogonal codes for incoherent optical CDMA systems,” IEEE J. Lightwave Technol., vol. 21, no 9, pp. 1869-1875, Step. 2003.
[50] Jen-Fa Huang and Dar-Zu Hsu, “Fiber-Grating-Based Optical CDMA Spectral Coding with Nearly Orthogonal M-Sequence Codes”, IEEE Photonics. Technol. Lett., vol 12, no. 9, pp. 1252-1254, Sept. 2000.
[51] J.F. Huang and C.C. Yang, “Reductions of Multiple-Access Interference in Fiber-Grating- Based Optical CDMA Network,” IEEE Trans. on Commun., vol. 50, no. 10, pp. 1680-1687, Oct. 2002.
[52] Chao-Chin Yang, “Hybrid wavelength-division-multiplexing/spectral-amplitude- coding optical CDMA system,” IEEE Photonics Technol Lett., vol. 17, no. 6, pp. 1343-1345, June 2005.
[53] J. E. Baran, G. Joyce, R. Olshansky, D. A. Smith, and S. F. Su, ”Gain equalization multiwavelength lightwave systems using acoustooptic tunable filters,” IEEE Photonics Technol Lett., vol. 4, no. 3, pp. 269-271, Mar 1992.
[54] P. M. J. Schiffer, C. R. Doerr, L. W. Stulz, M. A. Cappuzzo, E. J. Laskowski, A. Paumescu, L. T. Gomez and J. V. Gates, “Smart dynamic wavelength equalizer based on an integrated planar optical circuit for use in the 1550-nm region,” IEEE Photon. Technol. Lett., vol. 11, no 9, pp. 1150-1152, Step 1999.
[55] L. Nguyen, T. Dennis, B. Aazhang, and J. F. Young, “Experimental demonstration of bipolar codes for optical spectral amplitude CDMA communication,” IEEE J. Lightwave Technology., vol. 15, no 9, pp.1647-1653, Sept. 1997.
[56] T. Pfeiffer, B. Deppisch, M. Kaiser, and R. Heidemann, “High speed optical network for asynchronous multiuser access applying periodic spectral coding of broadband sources,” Electron. Lett., vol. 33, pp. 2141–2142, 1997.
[57] G. A. Magel, G. D. Landry, R. J. Baca, D. A. Harper, and C. A. Spillers, “Transmission of eight channels×622 Mbit/s and 15 channels×155 Mbit/s using spectral encoded optical CDMA,” Electron. Lett., vol. 37, no. 21, pp. 1307 – 1308, Oct. 2001.
[58] 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 comm., vol. 46, no.9, pp. 1176-1185, Sept. 1998.
[59] Govind P. Agrawal, “Fiber-Optic Communication Systems,” John Wiley & Sons, Inc., 1997.
[60] S. Ayotte, M. Rochette, J. Magne, L. A. Rusch, S. LaRochelle, “Experimental verification and capacity prediction of FE-OCDMA using superimposed FBG,” IEEE J. Lightwave Technol., vol. 23, no. 2, pp.724-731, Feb. 2005.
[61] S. R. Baker, H. N. Rourke, V. Baker, and D. Goodchild, “Thermal decay of fiber Bragg gratings written in boron and germanium codoped silica fiber,” IEEE J. Lightwave Technol., vol. 15, no. 8, pp 1470-1477, Aug. 1997.
[62] Zhou Xiang, H.H.M. Shalabu, and Chao Lu, “Design and performance analysis of a new code for spectral-amplitude-coding optical CDMA systems,” Spread Spectrum Techniques and Applications, 2000 IEEE Sixth International Symposium on vol. 1, pp 174 – 178, Sept. 6-8 2000.