100Gbit/s的資料傳輸速度在下一個世代的以太傳輸系統中是非常具有吸引力的，把這樣的高速傳輸應用在波分多工(WDM)系統中對建造一個有成本效益的光通訊網路是非常重要的。然而，要實現這樣的高速傳輸藉由傳統的振幅移鍵(ASK)技術是相當困難的。藉由正交頻分多工(OFDM)技術，則可以使用其他的調變方法取代傳統的振幅移鍵。由於使用這些調變技術在微波域比光域相對簡
單，因此藉由正交頻分多工技術來增加頻譜效率是比較容易的。這篇論文將會探討應用了正交頻分多工技術的100Gbit/s波分多工系統。針對8個頻道的100Gbit/s正交頻分多工系統的績效做了評估。模擬程式的結果顯示，所有頻道的誤碼率在500公里的傳輸之後都低於10-3，且可被正向錯誤更正改善。這個結果顯示應用了正交頻分多工的100Gbit/s傳輸系統的可能性。
成本是波分多工被動光網路最重要的考量。在波分多工被動光網路中，在兩端都必須設置光源以傳輸上行和下行的資料。在實際的應用上，在鄰近用戶端的光纖網路單元(ONU)開發一個低成本的光源是不可或缺的。為了發展一個簡單有效率的光纖網路單元，一個有潛力的作法是接受到來自交換中心(CO)的下行光後，重新調變成為上行光。這個方法可藉由在用戶端設置反射式半導體光放大器(RSOA)來實現，不需要在用戶端設置額外的光源。
對於傳統的光纖到家(FTTH)系統，下行和上行資料的調變方法都是強度調變直接檢測(IM/DD)。然而這個方法的缺點是再調變的上行光嚴重的受制於下行光的影響。為了解決這個問題，必須替換下行光的調變方法為另一種不同的調變方法，像是差分相位移鍵(DPSK)。在差分相位移鍵系統中，由於下行光的振幅並不會被調變，所以上行光不會下行光被影響。這篇論文主要在探討在兩種
不同的下行調變方法之下，再次調變的上行訊號品質。實驗結果顯示，針對上行訊號的品質，下行使用差分相位移鍵的調變模式比使用強度調變直接檢測要好，兩者的差異是17dB.

100Gbit/s transmission data rate is very attractive for the next generation Ethernet
transport systems, and this kind of high-speed channel based WDM systems is very
attractive for constructing cost-effective optical transport networks. However, it is
quite difficult to achieve such high bit-rate by using the conventional amplitude shift
keying (ASK) technology. For the subcarrier modulation of the orthogonal frequency
division multiplexing (OFDM) scheme, it is possible to use various modulation
formats. It is relatively easy to use such an advanced format in the microwave domain
compared to the optical domain. Therefore, it is possible to increase the spectral
efficiency relatively easily by using the OFDM technology. In this master thesis, 100
Gbit/s WDM system with OFDM is discussed. The performance of 8 channels
100Gbit/s OFDM system was evaluated. The simulation result showed that the BER
of all channels were below 10-3 after 500 km transmission, and the performance could
be improved by using the FEC. This result shows the possibility of 100Gbit/s
transmission system using the OFDM technology.
The major concern of WDM-PON system is the cost. For WDM-PON system, it
needs several light sources for downstream signals and upstream signals. For the
practical implementation of WDM-PON, it is essential to develop a low-cost light
source in the optical network unit (ONU). In order to develop a simple efficient ONU,
a promising solution is re-modulated the downstream signal from central office (CO)
as the upstream signal at ONU using reflective semicounductor optical amplifier
(RSOA) so that there is no need to setup an additional light source at the ONU side.
For the conventional fiber-to-the-home (FTTH) system, the modulation format for
both downstream signal and upstream signal is intensity modulation with direct
detection (IM/DD). The demerit of the IM/DD scheme for the FTTH system is that
the performance of the re-modulated upstream signal is limited by the interference of
the downstream signal. In order to overcome this issue, the IM/DD format of
downstream should be replaced by some different formats such as differential phase
shift keying (DPSK). As there is no amplitude modulation for the DPSK downstream
signal, the re-modulated signal will not be affected by the downstream signal.
Therefore, this master thesis is focusing on comparing the re-modulated signal quality
for both IM/DD downstream and DPSK downstream. The experimental results shows
that the upstream signal of the DPSK downstream case shows better performance than
the IM/DD downstream case, and the performance difference of the re-modulated
signal is 17dB.

致謝..........................................................................................................................................I
中文摘要.........................................................................................................................II
ABSTRACT...................................................................................................................III
List of abbreviations...........................................................................................................IV
Chapter 1 Introduction………………………………………………………………1
1.1 Technological trend of the accss network……………………………………1
1.2 The concept of current PON system……………………………………………2
1.2.1 TDM-PON…………………………………………………………………2
1.2.2 WDM-PON………………………………………3
1.3 Motivation of this thesis…………………………………………………………4
Chapter 2 Simulation study of 100 Gbit/s WDM transmission using OFDM and
NZDSF……………………………………………………………………8
2.1 Introduction……………………………………………………………………8
2.2 The concept of OFDM…………………………………………………………8
2.2.1 The basic theory of OFDM…………………………………………………8
2.2.2 The merit of OFDM………………………………………………………9
2.3 Simulation………………………………………………………………………10
2.3.1 Simulation method……………………………………………………….10
2.3.2 Simulation model…………………………………………………………10
2.3.3 Simulation results and discussions……………………………………11
2.4 Conclusion……………………………………………………………………14
Chapter 3 Theoretical study of IM/DD and DPSK format………………………17
3.1 Introduction……………………………………………………………………17
3.2 Basic theory of IM/DD and DPSK ……………………………………………17
3.2.1 IM/DD scheme…………………………………………………………17
3.2.2 DPSK format………………………………………………………………18
Chapter 4 Technical problems existed in the proposed WDM-PON system……21
4.1 Introduction……………………………………………………………………21
4.2 Crosstalks due to Rayleigh backscattering in bidirectional optical fiber
transmission system……………………………………………………………22
4.3 Technical issues exist in the re-modulation scheme………………………23
4.3.1 Power issue………………………………………………………………23
4.3.2 Second modulation of the upstream signal………………………………23
Chapter 5 Basic study of re-modulated signal quality for fiber-to-the-home
(FTTH)……………………………………………………………………26
5.1 Introduction……………………………………………………………………26
5.2 Experimental setup……………………………………………………………26
5.3 Results and discussions………………………………………………………29
5.4 Conclusions…………………………………………………………………37
Chapter 6 Summary………………………………………………………………39

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