隨著高畫質的隨選視訊服務(MOD)的問市，以及一般使用者對網路使用日益嚴重的依賴性來說，檢視目前普遍以xDSL為主體的最後一哩網路架構，皆無法滿足未來網路服務的頻寬需求？傳統電纜線的傳輸，速率往往取決於分享到的頻寬以及距離等之類的因素，若是要對每個用戶提供專線服務，以建置與設備的費用來看應該是不可能實現的方案。
被動光學網路的發展得到了網路營運商的青睞，現在已開始使用GPON的技術應用於實際光纖到家的系統中，並且10 Gbps EPON的規範也將於今年年底拍板定案，因此視為下階段網路架構趨勢的分波多工被動光學網路(WDM-PON)勢必要朝向雙向傳輸10 Gbps資料速率的方向邁進，才得以應付如此大量的頻寬需求。WDM-PON發展至今，較令眾人所矚目的重要技術，便是所謂的無色光源的特性，即系統架構中只由局端提供用戶端所需之光源作為上行之媒介，而在用戶端的部分，僅需具備能調變訊號之調變器即可。
本論文主要提出一新型交叉複調變(Cross-remodulation)的10 Gbps雙向高速傳輸WDM-PON網路架構之設計，加上使用了本實驗室已發展出的應用於氣體偵測用的雙波長DFB雷射作為頭端機房的主要光源，整體網路架構的特點包含: 1)大幅地解決WDM-PON系統最大問題—雷利散射，2)簡化了傳統架構上所需的額外提供給上行訊號用的光源數目，3)對於用戶端的10 Gbps ONU可能採用的元件，從量測頻率響應特性進行完整的評估，我們採用了特殊反射式設計的電致吸收調變器(REAM)作為ONU的調變器，4)配合雙波長DFB雷射輸出的兩個波段之波長，分別為S波段與L波段，可以將上下行傳輸訊號分別載於不同波段的光源上。經由實驗的成功驗證，上下行可以同時傳輸10 Gbps PRBS NRZ訊號，於經過25公里的單模光纖後，大約只增加1 ~ 1.5 dB光功率償付值(Power penalty)。
由於REAM元件本身具有高插入損耗特性，而上行傳輸訊號之光源必須經過整個傳輸線路來回兩次，光功率額度範圍(Power budget)是必須考慮的參數，因此也從模擬軟體VPI方面著手，探討將REAM結合SOA基體化的最佳參數設計與效能驗證。

The evolution of the passive optical networks attracts much attraction from the network providers. It begins with applying the GPON technology into the actual fiber-to-the-home solutions. Besides, the 10 Gbps EPON standards will be released this year. The next generation network technology after the TDM-PON is the WDM-PON. The network architecture must be able to provide 10 Gbps signal transmission for each node. The critical requirement in the WDM-PON systems is the colorless optical network unit (ONU) design. All multi-wavelength lightwave sources, including those for downstream and upstream transmission, must be placed at the optical line terminal (OLT) of the central office. In the ONU, a simple light source or modulator is used to transmit the upstream signal.
In this thesis, a novel WDM-PON network architecture is proposed for providing the 10 Gbps bidirectional transmission with a cross-remodulation skill. A special dual-wavelength DFB (DWDFB) laser provides the two wavelengths in different spectral bands for simultaneous transmission of downstream and upstream signals. This DWDFB laser was originally designed by our lab and for gas sensing applications. The advantages of this network architecture include: 1) the reduction of Raleigth backscattering of the WDM-PON system, 2) the use of half number of light sources. We also upgrade the upstream data rate to 10 Gbps and provide symmetric transmission. After measuring the small frequency response of various device candidates for 10 Gbps ONU, we choose to use a reflective electroabsorption modulator (REAM) in each ONU of our system. The output wavelengths of DWDFB laser locate at the S-band and L-band, so the upstream and downstream signals are transmitted at the different wavelength bands. We demonstrated experimentally that the upstream and downstream transmission 10 Gbps NRZ signals over 25-km single-mode fiber (SMF) can have only 1 ~ 1.5 dB power penalty.

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