在現今資訊爆發的年代,大量的資料傳輸以及高的傳輸速度是有所必要的。光纖通訊在這方面扮演著相當要的角色,常距離光纖通訊更是其中不可或缺的一個重要環節,所以去了解這樣的一門技術來改善傳輸的效能是一個非常重要的課題。就我們所知,色散平坦光纖(DFF)以及歸零碼差分向一件調變(RZ-DPSK),都兼具了有效改善傳輸效能的特色,所以把這兩個元素作結合將會是一門改善系統傳輸增益的重要技術。

在目前的長距離光纖通訊系統中色散圖是一項相當重要的技術,並且已經廣泛的使用在世界各地的海底光纖傳輸系統中,藉由不同的光纖組合所形成的色散變化 ,將對於傳輸效能有著關鍵性的影響,因此色散圖也是我們的研究重點.在本篇論文中,我們著重在長距離光纖通訊的理論模擬研究與探討.藉由改變色散圖的形態,探討色散圖中零號交叉點以及色散圖中不同的色散補償機制對整體傳輸效能上的影響,近而達到有效改善長距離光纖通訊系統的傳輸效能.

在這篇論文中,我們藉由數直模擬的方法發現到,色散圖中色散區塊的多寡會是一個決定傳輸效能好壞的重要關鍵,越多的色散區塊,表現在傳輸效能上的結果就越差, 反之,則越好,另外不同的光纖色散補償機制也是決定系統傳輸效能好壞的重要因素。另外我嘗試著去設計更理想化的色散圖, 以期能在傳輸效能上有所改進。

Nowadays Optical fiber communication is one of the important way to convey information, and there is strong competition in optical long-haul transmission to achieve high channel bit rates and large transmission capacity. Therefore, it is important to study a technology to improve the performance of such system. As we have already known, the dispersion flattened fiber (DFF) and Return-to-zero differential phase shift keying (RZ-DPSK) modulation are attractive, because it can improve the transmission performance of the long-haul system, therefore, it is possible to improve the transmission performance by a combination of the RZ-DPSK and the DFF, and the performance improvement investigation is required, because it will contribute to improve the system design of the long-haul optical fiber communication systems in near future.

In this master thesis, a theoretical study focused on the RZ-DPSK transmission system using DFF is conducted. One important technology of current long-haul optical fiber communication system is a dispersion map. In this master thesis, difference of the transmission performance is characterized with regard to number of dispersion blocks within the dispersion map, different repeater output power and different compensation scheme within dispersion map, etc., all of them calculated by a numerical simulator .The goal is to clarify the optimum dispersion map design of the long-haul DPSK based transmission and find the effective method to improve the transmission performance.

◎ 致謝 …………………………………………………………………………...Ⅲ

◎ Abstract………………………………………………………………………………........ Ⅳ

◎ 中文摘要………………………………………………………………………Ⅴ

1.1 Background of long-haul optical fiber communication system…………………...1
1.2 Motivation of this study………………...................................................................2
1.3 Structure of this thesis……………………………………………………………..3
Chapter2 Theoretical and technical background of this study
2.1 Theoretical background……………………………………………………………5
2.1.1 Nonlinear Schrödinger equation……………………………………………..5
2.1.2 Split-step Fourier method………………………………………………..…11
2.2 Technical background…………………………………………………………….14
2.2.1 Dispersion map……………………………………………………………..14
2.2.2 Dispersion flattened fiber…………………………………………………..16
Chapter3 Transmission performance of long-haul RZ-DPSK system
using DFF
3.1 Explanation of the simulation model…………………………………………….19
3.2 Comparison of block-type and blockless-type dispersion maps…………………21
3.2.1 Block-type and block-less type dispersion map……………………………21
3.2.2 Results of the simulation…………………………………………………...23
3.2.3 Discussions…………………………………………………………………25
Chapter 4 Efforts to improve the transmission performance of the
block-type dispersion map
4.1 Explanation of the basic ideas……………………………………………………27
4.1.1 Dispersion map shifting……………………………………………………27
4.1.2 Dispersion map tilting……………………………………………………...29
4.2 Reduction of zero crossing points by dispersion map shifting…………………..31
4.2.1 Dispersion map……………………………………………………………..31
4.2.2 Results and discussions…………………………………………………….35
4.3 Reduction of zero crossing points by dispersion map tilting…………………….38
4.3.1 Dispersion map…………………………………………………………..…38
4.3.2 Results and discussions………………………………………………….....49
Chapter 5 Conclusion…………………………………………………………..53
List of Abbreviation…………………………………………………………….55

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