在當前的傳輸系統中，傳輸量仍然不足，因為光纖通訊系統的可利用資訊頻寬受限於光放大器，所以要如何更有效率的運用頻寬是一件非常重要的議題。因此，振幅與相位移鍵控 (APSK) 在改善頻譜效率以及有效地增加傳輸量是一項很吸引人的調變技術。
進階的調變格式與同調檢測技術都可以有效的提高傳輸量以及頻譜效率。然而在同差檢測系統中，利用光鎖相迴路 (PLL) 鎖住本地振盪器 (LO) 與信號的相位仍舊很難實現而且使得其接收電路更加複雜。所以利用數位同調接收器接收信號後，再經由數位信號處理 (DSP) 即可恢復光載波的相位資訊，且透過數位信號處理的相位估計運算法後就不再需要光鎖相迴路了。儲存的資料可利用MATLAB程式離線處理計算。
本碩士論文著重在研究使用數位同調接收器與數位信號處理 (DSP) 後的振幅與相位移鍵控 (APSK) 傳輸表現，且進行497公里的傳輸實驗。接著，儲存的資料可藉由數位信號處理 (DSP) 的運算法達到離線處理計算。然後比較振幅與相位移鍵控 (APSK) 在傳輸前與497公里傳輸後的表現。

In the current transmission systems, the transmission capacity is still not enough. The information bandwidth of the optical fiber communication system is limited by the optical amplifier bandwidth, and more efficient use of the bandwidth is a very important issue. Therefore, the amplitude and phase shift keying (APSK) is one attractive method of multi-bit per symbol modulation scheme to improve the spectral efficiency, and it can effectively increase the transmission capacity.
To improve the capacity and the spectral efficiency, the advanced modulation format is effective, and the coherent detection scheme is also effective. However, an optical phase-locked loop (PLL) to lock the local oscillator (LO) phase and the signal phase required for the homodyne detection is still difficult to realize and it makes the receiver circuit complicated. Using the digital coherent receiver, the optical carrier phase information can be recovered by means of the digital signal processing (DSP), and this scheme enables to eliminate the optical PLL circuit by the phase estimation algorithm through the DSP. The stored data can be offline processed by using the MATLAB program.
This master thesis is focusing on studying the transmission performance of the APSK format using the DSP in the digital coherent receiver. 497km transmission experiment has been conducted. Subsequently, the stored data are offline processed by the algorithms of the DSP. Then, the APSK performances between back-to-back and 497km transmission are compared.

誌謝 i
中文摘要 iii
Abstract iv
Contents vi
List of Figures viii
List of Tables ix

1　Introduction 1
1.1　Coherent Optical Communication Systems 1
1.2　APSK Modulation Format and Extinction Ratio 3
1.2.1　APSK Modulation Format 3
1.2.2　Extinction Ratio 5
1.3　Motivation of this Thesis 6
1.4 Structure of this Thesis 7
References 9

2　Development of Digital Coherent Receiver 11
2.1　Introduction 11
2.2　Coherent Detection of Phase-diversity Homodyne Receiver 11
2.3　Algorithm of Digital Signal Processing 16
2.3.1　BER Calculation Algorithm 16
2.3.2　Optical Carrier Phase Estimation Algorithm 17
2.4　Conclusion 20
Attachments 21
References 27

3　Experimental Study of APSK 29
3.1　Introduction 29
3.2　Experimental Setup 29
3.2.1　Transmitter 30
3.2.2　Transmission Line 32
3.2.3　Receiver 36
3.3　Experimental Results and Discussions 38
3.3.1　Eye Diagram of the APSK Signal 38
3.3.2 APSK Transmission Performance 43
3.3.3　APSK Transmission Performance after Modifying 50
3.4　Conclusion 56
References 58

4　Conclusion 59

List of Acronyms x

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