臺灣博碩士論文加值系統

光纖通訊的重要性，已隨著現代工商業社會的發展而日益倍增。在光纖通訊網路系統中，光放大器的採用可以避免因為光電訊號間的轉換造成的訊號失真。進而提供更為遠距的傳輸以及容許更多被動元件造成的損耗。目前主流的光放大器為掺鉺光纖放大器，它其中之ㄧ的特性為固定的放大頻段。隨著網際網路的蓬勃發展，我們需要更多的頻寬來滿足日益增加的傳輸資料需求量。這一點卻是掺鉺光纖放大器所無法提供的。另一種光放大器，也就是本論文所著重的光纖拉曼放大器，因為具備放大頻段可調變的優點，正好符合此一趨勢的需求。以往高功率的拉曼激發光源取得不易的問題，隨著近來高功率的半導體及光纖雷射相繼的發展而獲得解決。因此光纖拉曼放大器的應用再度引起世人的目光。
光纖拉曼放大器對於高功率拉曼激發光源的需求原因，來自於現行廣為鋪設的光纖之中，拉曼增益係數相對為低的理由。為了達到適宜的增益，此一需求實無法避免。然而，高功率的光源勢必伴隨著嚴重的非線性問題。換言之，拉曼激發光源的特性將大大的影響光纖拉曼放大器的性能。有鑑於此，本論文著重在探討藉由變換光纖拉曼放大器的激發機制使得其在雜訊方面有更佳的表現。我們更進一步提出結合兩種不互相衝突的激發機制，可以使得其在雜訊方面的表現上有更好的改善。
此外，一般光纖拉曼放大器多是用來作為遠距離間的光放大器，但我們認為光纖拉曼放大器在雜訊方面的良好表現，也可以應用在都市間的區域網路中。我們比較了光纖拉曼放大器以及摻鉺放大器應用在被動光環網路中做為光放大器的表現。我們發現雖然光纖拉曼放大器的表現可以比摻鉺放大器較好，但是它對於元件的損耗十分敏感。由於在都市間的區域網路中，除了光纖以外還會有許多被動元件包含在內。在現實的情況下，相同的元件可能具有不同程度的元件損耗。我們進一步探討在有數個相同元件但有不同的損耗程度之下，如何將這些元件做適當的安排，以提高光纖拉曼放大器的效率。

The importance of optical fiber communication is increasing in modern world. In optical fiber communication system networks, the application of optical amplifiers can avoid the signal distortion from transformation between electrical and optical signals and then provide even longer transmission span and permit even more components regardless of the loss increment. At present, the dominant optical amplifiers are erbium-doped fiber amplifiers (EDFAs), which have a characteristic of fixed amplification bandwidth. With the rising of internet popularization, wider bandwidth is required to satisfy the increasing requirement of the data quantity. This demand is limited by EDFAs’ characteristic. Another optical amplifier, fiber Raman amplifier (FRA), which has the characteristic of flexible amplification bandwidth, is a candidate to fulfill this demand. The lack of high power Raman pump light in the past, is solved with the development of high-power semiconductor and fiber lasers. Now the application of FRAs attracts people’s attention again.
The demand of high-power Raman pump light in FRAs is due to the low gain coefficient of the existing optical fibers. To achieve a suitable gain level, this demand of high-power pump is unavoidable. However, the higher the pump power is, the more severe the nonlinearity problem will be introduced. The performance of Raman pump light will greatly affect the performance of FRAs. In this thesis, we first focus on the relationship between Raman pumping schemes and the noise performance of FRAs. We further propose a combined pumping scheme to achieve better performance.
Although FRAs are often used in long-haul systems, we believe they can also benefit metropolitan networks with its better noise performance. In this thesis, we also investigate the appropriate application of FRAs in passive optical ring networks. We find that the performance of FRAs is very sensitive to the component loss. Because in metropolitan networks, many passive components should be included in addition to optical fibers, they introduced additional losses. In practice, the components have different losses. We investigate the impact of component losses and provide a way to optimize the performance of the Raman amplifier through proper arrangement of these components with different losses.

Table of Contents
CHAPTER 1 INTRODUCTION 1
1.1. OPTICAL AMPLIFIERS IN OPTICAL COMMUNICATION 1
1.2. THESIS OUTLINE 2
Reference of Chapter 1 3
CHAPTER 2 THEORY OF FIBER RAMAN AMPLIFIERS 4
2.1. OVERVIEW OF OPTICAL AMPLIFIERS 5
2.1.1. Doped-Fiber Amplifiers 5
2.1.2. Semiconductor Optical Amplifiers 7
2.1.3. Fiber Raman Amplifiers 10
2.2. STIMULATED RAMAN SCATTERING 11
2.2.1. Spontaneous Raman Scattering 12
2.2.2. Stimulated Raman Scattering 14
2.2.3. Raman Gain Spectrum 15
2.3. FIBER RAMAN AMPLIFIERS 17
2.3.1. Small Signal Gain 18
2.3.2. Gain Saturation 19
Reference of Chapter 2 23
CHAPTER 3 NOVEL RAMAN PUMPING SCHEMES 24
3.1. PUMPING DIRECTIONS 25
3.1.1. Forward Pumping 25
3.1.2. Backward Pumping 27
3.1.3. Comparison 28
3.2. TIME-DIVISION MULTIPLEXING PUMPING SCHEME 31
3.2.1. Basic Concepts of TDM Pumping Scheme 32
3.2.2. Temporal Raman Gain Variations 33
3.2.3. ASE and DRS 40
3.3. HIGHER-ORDER PUMPING SCHEME 45
3.3.1. Basic Concepts 45
3.3.2. Experimental Results 47
3.4. COMBINED PUMPING SCHEME 50
3.4.1. Basic Concepts 51
3.4.2. Pumping Direction 53
Reference of Chapter 3 56
CHAPTER 4 APPLICATIONS OF FRAS IN PASSIVE OPTICAL RING NETWORKS 57
4.1. OPTICAL PASSIVE RING NETWORKS 58
4.1.1. The Architecture of the POR Networks 59
4.1.2. The Central Node of the POR Networks 60
4.1.3. The Parameters of the POR Networks 61
4.2. THE DESIGN OF AMPLIFIERS IN THE CENTRAL NODE 64
4.2.1. EDFA 64
4.2.2. Fiber Raman Amplifiers 67
4.2.3. Other Amplifiers 71
4.2.4. The Design Rules of Applying FRA 76
4.3. THE DESIGN OF COMPONENTS LOSS ARRANGEMENT 77
4.3.1. One Better OADM and Three Worse OADMs 77
4.3.2. Two Better OADMs and Two Worse OADMs 80
4.3.3. The Design Rules of Component Loss Arrangement 83
Reference of Chapter 4 84
CHAPTER 5 CONCLUSION 85
APPENDIX A AVERAGE POWER ANALYSIS MODEL 87

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