隨著各式網路需求快速的發展，例如高速商業網路、光纖到家或是光纖與無線通訊整合應用，光纖通訊流量需求逐年快速成長。在各種光學擷取網路技術中，因為成本的考量，目前以被動光學網路被最多研究團隊重視與討論。而為了滿足快速成長的網路需求，正交分頻多工技術也開始被考慮為下一世代被動光學網路的調變格式。
為了提升被動光學網路的系統表現，例如傳輸速度、誤碼率或是成本效益等，大多數的研究團隊都專注在中央機房傳輸設計或是用戶端的接收設計。因此，各種光學的調變與接收機制被提出來討論；然而，為了增加系統表現而更改用戶端的設計，往往伴隨著巨大的建置成本。在本論文研究中，我們提出了二個升級模組的概念：第一個是在遠端遙控端，我們透過簡單的被動光學原件，可以達到加倍通道的傳輸量以及用戶數的偏振態解多工模組；另一個是，透過空間路由的方式解決反向散射干擾的升級模組。兩個被提出的架構都不需要更動用戶端的設計，同時可以與分波多工系統相容；也因此可以提供系統供應商一個可以依照其市場需求的升級方案。
最後一個研究計畫是能均一化用戶下傳表現的強度調變系統。由於雙邊帶的訊號在傳輸後會受到射頻衰減的問題；不同頻率、不同接收位置的用戶也因此會有不同的訊號表現。然而，這樣不公平的接收表現不利於一般的商業模型。在本論文中，首次提出利用多載波分碼多址的調變格式來使0-100公里中各個使用者能有接近的接收表現。此外多載波分碼多址不僅與正交分頻多工擁有相同的通道容量與頻譜效益，其接收表現還可以透過數位演算法的方式進行進一步的提升，以獲得更好的系統功率預算值。

As the fast soaring of modern applications, e.g. high speed business networks, fiber to the home or fiber-wireless integration, the data rate requirement rapidly increases with the years in optical access networks. Due to its cost-effective nature, passive optical network (PON) attracts lots of attention by researchers. Meanwhile, to meet the future data rate requirement, orthogonal frequency division multiplexing (OFDM) is widely investigated and considering as one of the candidate signal formats for next generation PONs.
To enhance the performance of PON systems, including channel capacity, bit-error rate (BER) performance, and cost-effectiveness or so on, most of researchers focus on the transmitter design in the central office (CO) or the receiver design at optical network units (ONUs). Therefore, lots of modulation formats and/or receiving mechanisms are proposed for future requirements. However, enhancing the performance via modifying ONUs’ design always requires huge capital expenditures (CAPEX). In this dissertation, we propose two upgrade module concepts. First, in the powered remote node (RN), we can double the channel capacity and user numbers by passive optical polarization de-multiplexing implementation. The other one is a back propagation mitigation function by spatial routing. Both of them are highly compatible with existing wavelength division multiplexing (WDM) PON without any modification of ONUs’ design. System vendors can therefore upgrade the system depending on their marketing targets.
In the final chapter, an intensity modulation direct detection (IMDD) system is proposed with uniform downstream receiving performance among subscribers. In general, due to the double side band nature of IM signals, distinct users among different subcarrier in different locations will receive different BER performance caused by radio frequency fading loss. However, it is harmful to ordinary business model. Thus, we propose a multicarrier code division multiple access (MC-CDMA) signal format to uniform BER performance among subscribers ranging from 0 to 100 km. Moreover, the MC-CDMA signals’ performance can be further enhanced by appropriate digital signal processing. Therefore, power budget, which is typically limited by the worst user case, of the proposed MC-CDMA PON is improved with respect to the IMDD OFDM-PON.

List of Contents
Chapter 1. General Introduction 16
1.1 General Introduction of Optical Access Network 16
1.2 Introduction of PONs 18
1.3 Brief Introduction of the Proposed Schemes 20
Chapter 2. Principles 24
2.1 Downstream OFDM Processing 24
2.2 Intensity Modulation 26
2.3 Field Modulation 27
2.4 Reception of Single Band DDO-OFDM 28
2.5 Multiband OFDM Modulation 30
2.6 Multiple Access Technologies 33
2.7 Downstream MC-CDMA Processing 34
Chapter 3. A Carrier Centralized LR-PON with Multiband DDO-OFDM Downstream and Nyquist-QPSK Upstream 38
3.1 Introduction 38
3.2 Experimental Setup 40
3.3. Results 42
Chapter 4. Bi-directional 1 Tb/s DDO-OFDM Downstream and 480 Gb/s Nyquist Upstream WDM LR-PON with Back Propagation Mitigation 47
4.1 Introduction 47
4.2 Operation Principles 49
4.3 Experiment Setups 53
4.4 Experimental Results and Discussions 58
Chapter 5. Self-polarization Diversity PDM Module of DDO-OFDM in LR Optical Access Network 66
5.1 Introduction 66
5.2 Operation Principles 69
5.3 Experimental Setup and Results 73
5.3.1 Experimental Setup of Self-polarization Diversity PDM RoF 73
5.3.2 Experimental Results of Self-polarization Diversity PDM RoF 75
5.3.3 Experimental Setup of SOP Variation 81
5.3.4 Experimental Results of SOP Variation 82
5.3.5 Experimental Setup of Self-polarization Diversity Multiband DDO-OFDM PON 87
5.3.6 Experimental Results of Self-polarization Diversity Multiband DDO-OFDM PON 91
Chapter 6. RF Power Fading Mitigation for an IMDD Multicarrier LR-PON 95
6.1 Introduction 95
6.2 Experiment Setup and Results 99
6.2.1 Experiment Setup of 7.8 GHz Signals over 50-km Transmission 99
6.2.2. Experimental Results of 7.8 GHz Signals over 50-km Transmission 101
6.2.3 Experimental Setups of Users Ranging from BTB to 100 km Transmission with 10GHz Signal Bandwidth 104
6.2.4 Experimental Results of Users Ranging from BTB to 100 km Transmission with 10GHz Signal Bandwidth 105
6.2.5 Experiment Setup of Asynchronous MC-CDMA Upstream 111
6.2.6 Experimental Results of Asynchronous MC-CDMA Upstream 112
Chapter 7. Conclusions 116
7.1 Summary for this Dissertation 116
7.2 A Bi-directional LR-PON with Multiband DDO-OFDM Downstream and Nyquist-QPSK Upstream 116
7.3 A Bi-directional 1 Tb/s DDO-OFDM Downstream and 480 Gb/s Nyquist upstream WDM LR-PON with Back Propagation Mitigation 116
7.4 A Self-polarization Diversity PDM Module for the DDO-OFDM LR Optical Access Network Downstream 117
7.5 A Bi-directional IMDD MC-CDMA LR-PON in a RF Fading Channel 117
References 119
Symbols and Acronyms 124
Publication Lists 128

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