長距離密集分波長多工被動光網路之研究與分析

Abstract

本論文中我們針對長距離被動光網路 (LR-PON) 之架構、光譜使用效率、雷利背向散射雜訊和傳輸效能進行分析和討論。首先我們簡介接取式網路的演化過程，及從技術層面和經營層面探討推動接取式網路演化的動力。各種不同的研究挑戰都在本文中被一一介紹。 為了提高頻譜的使用效率，我們提出並實驗說明在分波長多工的LR-PON中使用正交分頻率多工技術 (OFDM)。由於正交振幅調變 (QAM) 的高頻譜效率，低頻的光通訊元件依然可以沿用。這代表著我們可以在不改變現有的GPON網路架構前提之下直接提升傳輸速率。此外，OFDM固有的多樣性傳輸使得傳輸的訊號能夠在接收端經由數位訊號處理進行頻率反應的等化。此特性能夠用來改善訊號在LR-PON中傳輸時的色散問題。 同時為了有效改善雷利背向散射雜訊，我們首先經由理論分析的方式介紹如何使用DD-MZM和DP-MZM產生CS-SSB載子。並使用所產生的CS-SSB載子進行訊號傳輸，訊號傳輸的結果也被加以討論和分析。 訊號的傳輸速度一直以來都是通訊系統中最受到重視的問題，為了能夠在提升傳輸速度的同時也讓成本符合經濟效益，我們提出ㄧ個簡單的高速LR-PON架構，此架構中我們使用四組10 Gb/s的通道成功達成40 Gb/s的訊號傳輸。同時我們也進行了單一通道40Gb/s的高速傳輸，並將傳輸的結果與前者互相比較。

This research makes four important contributions to the architecture, spectral efficiency, Rayleigh noise mitigation and capacity in LR-PON. First, we review the evolutionary path of access networks and show the drivers from technology and business perspectives for high bandwidth and low cost. A variety of research challenges in this field is reviewed. For spectral efficiency, we propose and demonstrate WDM LR-PONs that make use of OFDM signal. Due to the highly spectral efficiency of the QAM in each subcarrier of the OFDM signal, low-bandwidth optical components can still be used. This means we can directly increase the data rate of the system while using the existing optical components developed for GPONs. Besides, the inherent advantage of OFDM frequency diversity transmission allows simple equalization of frequency response by baseband digital signal processing (DSP). These characteristics can be used to mitigate fiber chromatic dispersion, which is one of the major impairments in LR-PONs. For Rayleigh noise mitigation, we first introduce the theoretical analysis of CS-SSB carrier generations using the DD-MZM-based and the DP-MZM-based ONUs. Then the transmission performances and the dispersion tolerances of the uplink signals generated by the two CS-SSB modulators are also analyzed and discussed. Results show that the CS-SSB signal generated by the DP-MZM has better transmission performance. Based on these results, an experiment WDM-LR-PON using carrier distribution with DP-MZM-based ONU is implemented and evaluated. For capacity in LR-PON, we propose a simple and efficient architecture to achieve 40 Gb/s LR TDM-PON deployment using four paralleled 10 Gb/s external modulated DFB-LDs module as transmitter. Besides, the proposed 40 Gb/s LR TDM-PON barely requires a moderate upgrade of the components at the ONU and the OLT. For confirmation, the transmission performance of 40Gb/s per-wavelength bit rate using three different kinds of modulation formats is simulated by using commercially available software (VPI TransmissionMakerV7.5). Our proposed scheme was experimentally demonstrated, showing the proposed scheme could be a promising candidate as a relatively simple solution for next-generation 40 Gb/s TDM-PON.