在進階的調變系統中，強度和相位調變（Amplitude and Phase Shift Keying）系統相當的受人矚目，最主要的不外乎頻譜效率較高，可以有效的增加傳輸量。在現今的傳輸系統中，可利用的頻寬被光放大器限制著，如何在有限的頻寬中更加有效率的使用頻寬變成一個非常重要的議題。本論文著重於研究模擬以及實驗強度和相位調變(APSK)的傳輸表現。
首先，我們做了一連串的模擬來探討理論分析。不論是強度調變（Amplitude Shift Keying）或者是相位調變（Phase Shift Keying）都會因為消光比（Extinction Ratio）的影響而使傳輸表現發生變化。本論文在此一部份探討了消光比對於APSK傳輸系統的影響，並且發現消光比的大小會對ASK及PSK的傳輸表現有反比的現象。換句話說，消光比大時，ASK的訊號比較好，PSK的訊號就會比較差。當消光比小時，ASK的訊號比較差，PSK的訊號就會比較好。為了要改進APSK的傳輸效率，本論文提出了一個方法改進傳輸效率，我們稱之為” Zero-nulling method”.這個方法改善了消光比造成傳輸表現反比的現象。並且我們利用模擬來證實了這個方法的可行性及是否有效率的增加。
接下來，我們著手進行實驗的架構。本論文中架設了330公里長的傳輸光纖，利用這個架構來確認模擬的成果是否正確。我們用實驗確認了ASK及PSK訊號傳輸上的表現，並且也確認了消光比對ASK及PSK訊號造成傳輸表現交易的影響。
另一方面，本論文架設500公里公里長光纖來探討長距離APSK傳輸的表現，利用再迴圈系統（recirculating loop）可以得到光纖傳輸數千公里的傳輸表現，並且本利用此實驗架構來確認了”Zero-nulling method” 的可行性。

Amplitude and Phase Shift Keying (APSK) format is one of the most attractive advanced modulation formats because of its good spectral efficiency. As the information bandwidth of the current optical fiber communication system is limited by the optical amplifier bandwidth, it is important to utilize the limited bandwidth effectively. This master thesis focuses on to study the transmission performance of the APSK format both theoretically and experimentally.

At first, a theoretical study was conducted using a numerical simulation. As the Extinction Ratio (ER) of the Amplitude Shift Keying (ASK) signal affects the performances of both the ASK and the Phase Shift Keying (PSK) signals, the effect of the ER upon the transmission performance of the APSK format was studied. A clear trade-off between the performance of the ASK signal and the PSK signal due to the change of the ER was observed. Then, in order to improve the performance of the APSK format, a method to improve the transmission performance was proposed. This method was named as “zero-nulling method”, and it solved the trade-off issue caused by the ER. The effectiveness of this method was confirmed through the numerical simulation.

Next, an experimental study was conducted. An experimental setup including 330km optical fiber transmission line was prepared, and it was used to confirm the results of the theoretical simulation. The performance trade-off between the ASK and the PSK signals due to the ER was confirmed experimentally.

Finally, another experimental study was conducted. An experimental setup of 500km transmission line was used for this study. By adopting the recirculating loop experimental setup, the transmission length could be extended to a few thousand kilometers. The applicability of the “zero-nulling method” was confirmed using this experimental setup.

◎致謝..…………….…………………...…………………………..……… I
◎中文摘要…..……………….…..………………...………………..……. II
◎Abstract………………………………………..………...………....……III
◎List of Contents……………………………...……………….………… IV
Chapter 1 Introduction 1
1.1 The background of optical fiber communication system 1
1.2 Motivation of this thesis 2
1.3 The structure of this thesis 3

Chapter 2 Simulation study of the APSK format using zero-nulling method 6
2.1 Introduction 6
2.2 Simulation method of the APSK system 6
2.2.1 APSK format 6
2.2.2 Extinction Ratio 7
2.2.3 Method of simulation 7
2.3 Simulation results of the APSK format and zero-nulling method 11
2.3.1 Simulation model of the APSK system 11
2.3.2 Simulation results of the APSK transmission 13
2.3.3 Zero-nulling APSK format 14
2.3.4 Simulation results of the zero-nulling APSK transmission 15
2.4 Conclusion 17

Chapter 3 Experimental investigation of APSK format focusing on extinction ratio 18
3.1 Introduction 18
3.2 Experimental setup 18
3.2.1 Transmitter 19
3.2.2 Transmission line 19
3.2.3 Receiver 22
3.3 Results and discussions focusing on the effect of the ER 23
3.3.1 Optical spectrum of the transmission line 23
3.3.2 Eye diagram of the ASK and the PSK signals 25
3.3.3 Performance of the ASK signal 28
3.3.4 Performance of the PSK signal 29
3.4 Conclusion 30




Chapter 4 Experimental investigation of the APSK format using zero-nulling method 31
4.1 Introduction 31
4.2 Experimental setup 31
4.2.1 Experimental setup of the APSK system with the recirculating loop 31
4.2.2 Recirculating loop 32
4.2.3 Setup to test the zero-nulling APSK system 34
4.3 Results and discussions 37
4.3.1 OSNR performance of the recirculating loop 37
4.3.2 Performance of the long distance transmission 40
4.3.3 Performance of the APSK format using the zero-nulling method 40
4.4 Conclusion 43

Chapter 5 Discussion of simulation and experimental results 44
5.1 Introduction 44
5.2 Discussion of the simulation results 44
5.3 Discussion of the experimental results 46
5.4 Comparison of the results of the theoretical studies and the experimental investigations 54

Chapter 6 Conclusions 56
List of abbreviations 58

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