光通訊網路裡提供了許多優點，如大頻寬、高資料傳輸速率、無電磁干擾和低損耗。隨著資訊傳輸的快速發展，在光網路中安全性和保密性的議題得到愈來愈多的重視。因此，有著保密性和高度彈性的光分碼多重擷取(OCDMA)技術成為近年來學者研究的目標。
儘管與其他類型存取網路技術比較，如分時多工(TDM)和分波多工(WDM)，傳統的OCDMA具有良好的隱密性和彈性，但仍然無法防止被無授權的使用者竊聽資訊。因此，本篇論文提出利用PRNMC演算法進行可重構的波長和變異碼來提升光網路傳輸的安全性和保密性。此安全機制是建立在利用混沌序列來映射擾序的控制值，產生變異碼和載波隨機的變化。此控制值被用來當作系統的密鑰並同步地從傳送端傳輸於私密通道至接收端。當控制端接收到正確的密鑰，就能進行正確的解碼並藉由PRNMC演算法恢復各別使用者的資料位元。透過不斷地重新配置各別使用者的變異碼和載波，竊聽者在不知道蜜鑰的情況下會更難以破解正確的資訊。
本篇論文的分析會分成兩部份，第一部份是PRNMC演算法的分析，包含帳篷映射(Tent map)和兩種映射方法的敏感性、重複碼字的使用率和熵(entropy)值在不同架構的比較。第二部分會分析各別使用者的碼字被竊聽的機率，除了比較不同架構，也會比較理想和實際的重新配置碼字時間下的效能。

An optical communication network provides many advantages, such as large bandwidth, high data rate, no electromagnetic interference and low loss. According to information transmission rapid development, the confidentiality and security issue in the optical network is getting more and more attention. Therefore, optical CDMA has high flexible network and confidentiality that is the research target in recent decades.
Compared with the other access network, such as TDM, and WDM, the conventional OCDMA architecture has high privacy and large flexibility, but it is still vulnerable to being eavesdropped by unauthorized user. Therefore, the reconfigurable code and wavelength scheme with PRNMC algorithm in optical network is proposed to enhance the security and confidentiality. The secure mechanism is established in utilizing the chaos sequence to map the disordered control value, and making more random variation of the codeword and wavelength. The control value is as secret key to transmit from transmitter to receiver synchronously. Only obtaining the right secret key as the transmitter, the decoder can recover the user’s data bit due to the PRNMC algorithm. The reconfiguration of each user’s codeword makes the eavesdropper crack the correct information more difficultly without obtaining the secret key.
In this study, the performance evaluation is divided into two parts. Firstly, the PRNMC algorithm will be analyzed including the sensitivity of Tent map, two mapping method, repetition of codeword, and the entropy value with different scheme. Secondly, for each user’s codeword, the probability of being eavesdropped will be discussed between different schemes, and compared in ideal and real reconfiguration time.

[1] G. Kramer and G. Pesavento, "Ethernet passive optical network (EPON): Building a next-generation optical access network," IEEE Commun. Mag., vol. 40, pp. 66-73, Feb. 2002.
[2] W. Ford, Computer Communications Security, Ch. 2, Upper Saddle River, NJ: Prentice-Hall, 1994.
[3] P. Prucnal, M. Santoro, and T. Fan, “Spread spectrum fiber optic local area network using optical processing,” IEEE J. Lightwave Technol., vol. LT-4, no. 5, pp.547-554, May 1986.
[4] J. A. Salehi, “Emerging OCDMA communication systems and data networks,” J. Optical Network, vol. 6, pp. 1138-1178, Sept. 2007.
[5] J. P. Heritage and A. M. Weiner, “Advances in spectral optical code-division multiple-access communications,” IEEE J. Sel. Top. Quant. Electron., vol. 13, pp. 1351-1369, Sept.-Oct. 2007.
[6] 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, Apr. 1993.
[7] K. S. Kim,” On the evolution of PON-based FTTH solutions,” Information Sciences—Informatics and Computer Science: An International Journal, vol.149, pp.21-30, Jan 2003.
[8] D. Sudhir, “IP Over WDM: building the next-generation optical internet,” Wiley-Interscience, pp. 533, 2003.
[9] 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.
[10] J. P. Heritage and A. M. Weiner, “Advances in spectral optical code-division multiple-access communications,” IEEE J. Sel. Top. Quant. Electron., vol. 13, pp. 1351-1369, Sept.-Oct. 2007.
[11] H. P. Sardesai, C. C. Chang, and A. M. Weiner, "Encoding and decoding of femtosecond pulses for code division multiple access communication systems using a pair of fiber-pigtailed pulse shapers," the 10th LEOS '97 Conference Proceedings, IEEE, pp. 310-311 vol. 2, 1997.
[12] J. A. Salehi, “Emerging OCDMA communication systems and data networks,” J. Optical Network, vol. 6, pp. 1138-1178, Sept. 2007.
[13] A. M. Weiner, Z. Jiang, and D. E. Leaird, “Spectrally phase-coded O-CDMA [Invited,]” Journal of Optical Networking, vol. 6, pp. 728-755, Jun 2007.
[14] S. J. B. Yoo, J. P. Heritage, V. J. Hernandez,” Spectral phase encoded time spread optical code division multiple access technology for next generation communication networks [Invited],” Journal of Optical Networking, vol. 6, pp. 1210-1227, Oct 2007.
[15] Xu Wang, N. Wada, T. Hamanaka, J. Kitayama and A. Nishiki, "10-user, truly-asynchronous OCDMA experiment with 511-chip SSFBG en/decoder and SC-based optical thresholder," OFC/NFOEC Technical Digest. Optical Fiber Communication Conference, 2005., vol. 5, pp. 3, 2005.
[16] J. A. Salehi, A. M. Weiner and J. P. Heritage, "Coherent ultrashort light pulse code-division multiple access communication systems," in Journal of Lightwave Technology, vol. 8, no. 3, pp. 478-491, Mar 1990.
[17] H. P. Sardesai, C.-C. Chang, and A. M. Weiner, "A Femtosecond Code-Division Multiple-Access Communication System Test Bed," J. Lightwave Technol., vol. 16, pp.1953-1964, 1998.
[18] A. Stok and E. H. Sargent, “The role of optical CDMA in access networks,” IEEE Commun. Mag., vol. 40, no. 9, pp. 83–87, Sept. 2002.
[19] W. Huang, M. H. M. Nizam, I. Andonovic and M. Tur, "Coherent optical CDMA (OCDMA) systems used for high-capacity optical fiber networks-system description, OTDMA comparison, and OCDMA/WDMA networking," IEEE J. Lightwave Technol., vol. 18, no. 6, pp. 765-778, June 2000.
[20] S. J. Park, C. H. Lee, K. T. Jeong, H. J. Park, J. G. Ahn, and K. H. Song, "Fiber-to-the-home services based on wavelength-division-multiplexing passive optical network," IEEE J. Lightwave Technol., vol. 22, pp. 2582-2591, Nov. 2004.
[21] 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, Mar. 1995.
[22] T. H. Shake, “Security performance of optical CDMA against eavesdropping,” IEEE J. Lightwave Technol., vol. 23, pp. 655-670, Feb 2005.
[23] T. H. Shake, “Confidentiality performance of spectral-phase-encoded optical CDMA,” IEEE J. Lightwave Technol., vol. 23, pp. 1652-1663, Apr 2005.
[24] Y. T. Chang, C. C. Sue and J. F. Huang, "Robust Design for Reconfigurable Coder/Decoders to Protect Against Eavesdrop-ping in Spectral Amplitude Coding Optical CDMA Networks," IEEE J. Lightwave Technol., vol. 25, no. 8, pp. 1931-1948, Aug. 2007.
[25] Y. T. Chang, C. C. Sue and J. F. Huang, "Signatures reconfigurations over waveguide-gratings-based optical CDMA network codecs," the 9th International Conference on Photonics (ICP 2014), Kuala Lumpur, Malaysia, September 2-4, 2014.
[26] Y. T. Chang, C. W. Tsailin and Y. C. Huang, "Dynamic reconfigurable AWG-based encryption and decryption with integrated chaos/M-sequence mapping algorithm for secure transmission," 2015 International Symposium on Next-Generation Electronics (ISNE), Taipei, pp. 1-3, 2015.
[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,” J. Lightwave Technol., vol. 19, no. 9, pp. 1274-1281, Sep. 2001.
[28] H. Takahashi, K. Oda, and H. Toba, “Impact of Crosstalk in an Arrayed-Waveguide Multiplexer on N×N Optical Interconnection,” IEEE J. Lightwave Technol., vol. 14, no. 6, pp. 1097-1105, June 1996.
[29] J. F. Huang and D. Z. Hsu, "Fiber-grating-based optical CDMA spectral coding with nearly orthogonal M-sequence codes," IEEE Photonics Technology Letters, vol. 12, no. 9, pp. 1252-1254, Sept. 2000.
[30] S. V. Maric and E. L. Titlebaum, “A Class of Frequency Hop Codes with Nearly Ideal Characteristics for Use in Multiple-Access Spread-Spectrum Communications and Radar and Sonar Systems,” IEEE Transactions on Communications, vol. 40, no. 9, pp. 1442-1447, September 1992.
[31] G. Jakimoski and L. Kocarev, "Chaos and Cryptography: Block Encryption Ciphers Based on Chaotic Maps," IEEE Transactions on Circuits and Systems—I: Fundamental Theory and Applications, vol. 48, no. 2, Feb. 2001.
[32] L. Kocarev, "Chaos-based cryptography: a brief overview," in IEEE Circuits and Systems Magazine, vol. 1, no. 3, pp. 6-21, Third Quarter 2001.
[33] W. F. Hassan and M. A. Mahiub, “Some Dynamical Properties of the Family of Tent Maps,” Int. Journal of Math. Analysis, vol. 7, no. 29, pp. 1433-1449, 2013.
[34] Y.T. Chang*, C.W. Tsailin, "Dynamic scrambling scheme of arrayed-waveguide grating-based encryptors and decryptors for protection against eavesdropping," Computers and Electrical Engineering, vol.49, no. 1, pp. 184-197, Jan 2016.
[35] Y.T. Chang, Y.C. Lin*, "Dynamic Reconfigurable Encryption and Decryption with Chaos/M-Sequence Mapping Algorithm for Secure H.264/AVC Video Streaming over OCDMA Passive Optical Network," Multimedia tools and Application, vol.75, no. 16, pp. 9837-9859, Aug 2016.
[36] V. Jyoti, R. S. Kaler, "Security enhancement of OCDMA system against eavesdropping using code-switching scheme," Optik-International Journal for light and Electron Optics, vol. 122, pp. 787-791, May 2011.
[37] M. C. Parker, A. D. Cohen, and R. J. Mears, "Dynamic Digital Holographic Wavelength Filtering," Journal of Lightwave Technology, vol. 16, no. 7, 1998.
[38] Y. K. Yeo, Z. Xu, D. Wang, J. Liu, Y. Wang, and T. H. Cheng, "High-speed optical switch fabrics with large port count," Opt. Express, vol. 17, pp. 10990-10997, 2009.
[39] Y. T. Chang, J. F. Huang, Y. C. Chen, "Security Enhancement on Programmable Spectral Phase Coding with Chaotic-Triggered Array," Optics & Photonics Taiwan, the International Conference (OPTIC’16), Taipei, Taiwan, Dec. 3-5, 2016.