下一代載波分佈光網路的新穎調制格式

Abstract

由於銅綫本身無法提供未來接入式網路所需要的低成本高效率寬頻傳輸，光纖會是 未來接入式網路的主要傳輸媒介。本計畫將研究新穎重要的光學信號調制格式和光電器 件，運作在10Gb/s 並用於下一代載波分佈光網路中，例如，被動光纖網路（PON）。PON 在未來5-10 年内需要一個大的升級來應付來自終端用戶的帶寬要求。由於它的低成本高 效率，PON 被認爲是最吸引的光接入式結構。PON 的基礎結構由很多用戶分享而且在電 信供應商和用戶之間的通道中沒有有源元件，比如電開關或路由器。第一代的PON 現 在已經被標準化，其中最先進的是GPON 和GE-PON，它們通常提供在上限20km 範圍 内，通過被動分光器，對共享的32 位用戶提供 ~2.5Gb/s 下行和 ~1Gb/s 上行的數據傳輸。 爲了充分利用光纖，本項目採用了密分波多工技術（DWDM）。利用研發的新型光網路 單元（ONU）和光學調制格式，更好的瑞利 （Rayleigh）反向散射噪音和色散允許誤差 可以在沒有改變現存的光網路基本機構的情況下實現。本項研究應可幫助國內接入式網 路的實現，它的長遠影響在於其導致的高速寬帶連接技術發展能確保臺灣的光通訊技術 保持在21 世紀知識經濟的的最前列。 長距離，高分流比，使用單一的分布/下載光纖，以及無色ONU 都是低成本高效率 的DWDM-PON 的必需元素。其中需要研發的核心技術包括新穎的調制方案，例如載波 抑制光雙二進制碼（carrier-suppressed-duobinary）等，來提高Rayleigh 噪音和色散的允許 誤差並且使分流比增加。另外爲了波長重用，我們將研究有效的波長再調制方案，例如 差分相移鍵控(differential-phase-shift-keying)上行和下行數據的再調制，並且也將建立多波 長DWDM 載波分佈光網路的試驗平台。光調制格式和光器件不僅可以用於PON，而且 還適用于不同載波分佈網路中以提高Rayleigh 反向散射噪音的允許誤差。建好的試驗平 台也可以用於其他的光網路實驗，例如radio-over-fiber 網路或者光封包交換網路 (optical-packet-switched-networks)等。

Copper cables alone cannot provide a cost-effective delivery of the sustained bandwidths needed in future access networks. This project develops novel and important optical modulation formats and optoelectronic components, operating at ~10Gb/s, used in next generation carrier distributed optical networks, e.g. passive-optical-networks (PON), which require strong upgrade in the next 5-10 years in order to cope with the exponential increase in the bandwidth demand by end-users. PON is regarded as one of the most attractive optical access architectures, since it is highly cost-effective. The PON infrastructure is shared by many customers and has no active components, such as electronic switches or routers, in the path between the telecommunication provider’s head-end office and the customers. The first generations of PONs are now standardized; the most advanced of these (GPON and GE-PON) typically offer ~2.5Gb/s downstream and ~1Gb/s upstream, shared between 32 customers via passive optical splitters. To fully utilize the optical fiber, dense-wavelengthdivision- multiplexing (DWDM) is used in this project. By developing novel optical-networking-units (ONU) and optical modulation formats, better Rayleigh-backscattering-noise and chromatic-dispersion tolerances can be achieved without changing the existing optical network infrastructure. The research will identify the requirements of access networks for Taiwan. The long term impact of this research is to ensure that Taiwan’s information technology infrastructure remains at the forefront for the knowledge based economy of the 21st century. Long-reach, high split-ratio, using single distribution/drop fiber and colorless ONUs are all necessary factors for cost-effective DWDM-PON deployment. The core technologies to be developed include the novel modulation schemes, e.g. carrier-suppressed-duobinary (CSD), to enhance the Rayleigh noise and dispersion tolerances for increasing the split ratio. Besides, effective wavelength remodulation schemes, e.g. differential-phase-shift-keying (DPSK) upstream and downstream remodulation, will be developed for wavelength reuse. DWDM carrier distributed optical network test-bed will be set up. The optical modulation formats and components developed cannot only be applied to the PON, but also applicable to different kinds of carrier distributed networks to enhance the Rayleigh-backscattering noise tolerance. The constructed test-bed can also be applicable for other optical network experiments, such as radio-over-fiber networks or optical packet switched networks.