隨著消費性電子產品的普及與網路使用習慣的改變，近年來訊號的傳輸速率比起往年呈現指數型增長，隨之而來的硬體升級亦是建置成本上的一大挑戰。在都會型網路的架構中，如何沿用現有的硬體並提升資訊傳輸量，並以低成本實現用戶端的接收與上傳，是現在網路系統中熱門的議題。
本論文首先敘述DDO-OFDM的產生與接收原理，再描述被動光學網路的演進與OFDM PON的優勢。以多頻帶DDO-OFDM作為基底，應用於被動光學網路的架構中作為下傳，並搭配多頻帶Nyquist QPSK上傳，完成一套PON的系統。在實驗上證明在同一光纖中傳輸時，操作時同波長的上下傳訊號會因瑞利反向散射(Rayleigh backscattering)而影響訊號品質，並提出一套可以迴避瑞利反向散射的模型運用在PON之上，並進一步擴展成八通道的WDM系統。此外，為再提升訊號傳輸量，論文中提出一套可相容於原系統上的被動偏振多工模組，並與主動的偏振多工系統相比較，使系統提升一倍的傳輸效率。

In recent years, with the popularity of consumer electronics products and network usage, the data rate of signal transmission has been increasing exponentially. How to upgrade the hardware while remaining low cost is a challenge. Therefore, It is a hot topic to enhance the data rate on existing hardware. So that, the transiver cost of network users can be reduced.
In this thesis, we explained the generation and reception of DDO-OFDM, the evolution of passive optical network (PON) and the advantage of OFDM PON. Then, the PON system was realized based on multi-band OFDM downstream and multi-band Nyquist QPSK upstream. In the PON system, we verified the Rayleigh backscattering (RBS) interferes between upstream and downstream signals if signals ware operated in the same frequency and fiber. Then, we proposed and demonstrated a model that could avoid RBS in a combined bi-directional system. By this system, eight channels WDM system has been realized. Beside, we demonstrated a passive polarization division multiplexing (PDM) receiving system, which can double the data rate in the existing PON system.

[1] http://www.telegeography.com/research-services/global-bandwidth-research-service/index.html
[2] R. W. Chang, “Synthesis of band-limited orthogonal signals for multi-channel data transmission,” Bell System Technology Journal 45(10), pp. 1775-1796 (1966)
[3] S. J. Savory, “Digital signal processing options in long haul transmission,” in Optical Fiber Communication Conference, paper OTuO3, San Diego (2008)
[4] Y. Ma, Q. Yang, Y. Tang, S. Chen, and W. Shieh, “1-Tb/s single-channel coherent optical OFDM transmission over 600-km SSMF fiber with subwavelength bandwidth access,” Optics Express 17(11), pp. 9421-9427 (2009).
[5] J. Yu, Z. Dong, and N. Chi, “1.96 Tb/s (21x100 Gb/s) OFDM optical signal generation and transmission over 3200-km fiber,” IEEE Photonic Technology Letter 23(15), pp. 1061-1063 (2011).
[6] W. R. Peng, I. Morita, H. Takahashi, and H. Tanaka, “Transmission of high-speed (> 100 Gb/s) direct-detection optical OFDM superchannel,” Journal of Lightwave Technology 30(12), pp. 2025-2034 (2012).
[7] L. Mehedy, M. Bakaul, A. Nirmalathas, and E. Skafidas, “Scalable and spectrally efficient long-reach optical access networks employing frequency interleaved directly detected optical OFDM,” IEEE Journal of Optical Communication Networking 3(11), pp. 881-890 (2011).
[8] N. Cvijetic, M. F. Huang, E. Ip, Y. Shao, Y. K. Huang, M. Cvijetic, and T. Wang, “Coherent 40Gb/s OFDMA-PON for long-reach (100+ km) high-split ratio (>1:64) optical access/metro networks,” in Optical Fiber Communication Conference, paper OW4B.8, Los Angeles (2012).
[9] A. J. Lowery, “Amplified-spontaneous noise limit of optical OFDM lightwave systems,” Optics Express 16(2), pp. 860-865 (2008).
[10] R. I. Killey, P. M. Watts, V. Mikhailov, M. Glich, and P. Bayvel, “Electronic dispersion compensation by signal predistortion using digital processing and a dual-drive Mach-Zehnder modulator”, IEEE Photonic technology Letters 17(3), (2005).
[11] A. J. Lowery, “Improving sensitivity and spectral efficiency in direct-detection optical OFDM systems,” in Optical Fiber Communication Conference, paper OMM4, San Diego (2008).
[12] N. Ansari and J. Zhang, Media Access Control and Resource Allocation for Next Generation Passive Optical Networks, Springer (2013).
[13] C. Gao, G. Farrell, “Modelling of Rayleigh backscattering on plastic optical fiber”, High Frequency Postgraduate Student Colloquium, IEEE UK and Ireland section, Belfast, Northern Ireland (2003).
[14] S. D. Personick, “Photon probe—an optical-fiber time-domain reflectometer,” Bell System Technical Journal 56(3), pp.355–366 (1977).
[15] J. H. Yan, Y. W. Chen, K. H. Shen, and K. M. Feng, “A 1:128 high splitting ratio long reach PON based on a simple receiving design for ONU with 120-Gb/s double-sided multiband DDO-OFDM signal,” in Optical Fiber Communication Conference, paper JW2A.74, Anaheim (2013).
[16] A. Chowdhury, H.C. Chien, M. F. Huang, J. Yu, G. K. Chang, “Rayleigh backscattering noise-eliminated 115-km long-reach bidirectional centralized WDM-PON with 10-Gb/s DPSK downstream and remodulated 2.5-Gb/s OCS-SCM upstream signal,” IEEE Photonics Technology Letters 20(24), (2008).
[17] C. W. Chow, C. H. Yeh, Y. F. Liu, C. H. Wang, C. L. Wu, S. Chi, “Carrier distributed PON using SSB-CS signal for rayleigh backscattering suppression,” in 15th OptoeElectronics and Communications Conference, paper 7P-07, Sapporo (2010).
[18] C. H. Yeh, C. W. Chow, and H. Y. Chen, “Simple colorless WDM-PON with Rayleigh backscattering noise circumvention employing m-QAM OFDM downstream and remodulated OOK upstream signals,” Journal of Lightwave Technology 30(13), pp. 2151-2155 (2012).
[19] S. L. Jansen, I. Morita, T. C. W. Schenk, H Tanaka, “121.9-Gb/s PDM-OFDM transmission with 2-b/s/Hz spectral efficiency over 1000 km of SSMF”, Journal of Lightwave Technology 27(3), pp.177-188 (2009).
[20] C. C. Wei, C. T. Lin, C. Y. Wang, F. M. Wu, “A novel polarization division multiplexed OFDM system with a direct-detection BLAST-aided receiver,” in Optical Fiber Communication Conference, paper JTh2A.49, Anaheim (2013).
[21] W. R. Peng, K. M. Feng, A.E. Willner, “Direct-detected polarization division multiplexed OFDM systems with self-polarization diversity” in 21st Annual Meeting of the IEEE Lasers and Electro-Optics Society, paper MH3, Acapulco (2008).