【作者】 Ahmed Muddassir Khan（可汗）；

【导师】 张杰；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2013， 博士

【摘要】 在接入网中部署光纤是一种可以满足未来带宽迅猛增长需求挑战的首选方式,且这种趋势已成为人们的必然选择。无源光网络(PON)是一种基于时分复用(TDM)光网络节点共享和简单低成本单波长光纤传输的系统方案,并已经成为光通信的重要技术。然而,TDM-PON尚面临若干关键挑战,例如高分离损耗、有限数量的光网络节点(ONUs)、系统的集合带宽、功率预算和传输距离受限等。为了解决上述问题,人们采用了波分复用无源光网络技术。但是对于WDM-PON的进一步实现而言,还有很多瓶颈尚待进一步研究,诸如设计复杂度较高、低消光比、接收机灵敏度较低、铺设成本高、低频谱效率、带宽利用率和波长共享率较低等。针对波分复用无源光网络所面临的各类挑战,本论文涵盖了全面而具体的理论性分析。为了实现高带宽利用率和波长共享率的混合波分／时分无源光网络,我们采用了基于差分四相相移键控和反转归零码的稳健的高级调制格式、低成本单光纤双向架构、高频谱效率设计的信道间隔等。本论文的关键创新点和工作如下：第一,为了应对无源光网络传输质量下降、数据速率和距离受限等,创新性地提出采用稳健先进调制格式,并在下行数据流中采用DQPSK、在上行数据流中采用反转归零码,并实现了更高的消光比和数据速率、改进的接收机灵敏度技术等。通过采用Optisystem7.0仿真分析系统传输性能,同时得到了星座图中优良的符号实例、清晰的眼图和低传输功率代价等。系统仿真结果表明,我们所提出的设计方案对于系统的传输损伤具有良好的容忍度。第二,波分复用无源光网络铺设的相对较高的成本是一个重要挑战。在本论文中,通过在传输双向上采用稳健的高级调制格式、色散补偿光纤、掺铒光纤放大器等,我们提出了一种低成本的、基于强度再调制的中心光源波分复用无源光网络技术。通过使用单光纤双向传输并充分考虑后向散射噪声等因素,可以进一步降低铺设成本。仿真结果表明,这种低成本波分复用无源光网络可以成功实现20—25公里传输,并具备较低的系统传输功率代价。第三,在过去几年中,高带宽需求的爆炸式增长是一个尚待解决的重要问题。为了实现更高容量,可以采用增加波长信道的数据速率、或者减少毗邻波长之间的信道间隔以增加更多的波长信道等方式。因此,本论文中另外一个重要工作是高频率效率波分复用无源光网络的相关设计。在波分复用无源光网络中16个信道的双向传输中,我们采用50GHz信道间隔取代100GHz信道间隔。对于传输系统性能的仿真和分析表明,系统具有更小的噪声代价。第四,如何使得带宽被高效率使用?这是我们所关心的另外一个重要问题。它可以通过光网络单元之间的波长共享、并采用时分复用技术来实现。因此,我们针对混合波分／时分复用的无源光网络,设计了一个高频谱效率方案,包括同时采用波分复用和时分复用技术的潜在优势等。所提出的系统设计可以支持256个光网络单元,且对于每个用户而言,上行和下行数据传输速率分别可以达到156Mbit/s和625Mbit/s.此外,仿真结果表明,该系统的传输功率代价可以基本被忽略,印证了优良的系统性能。因此,对于下一代大容量接入网而言,本研究论文为实现简单稳健设计、低成本铺设、高频谱效率架构、高带宽利用率和波长共享率等研究工作提供了一定基础。更多还原

【Abstract】 The trend of deployment of optical fiber in the access network has become ultimate choice because of its evaluation as a leading candidate to compete the challenges of drastic growth of bandwidth demands in future. In this contest, Passive Optical Networks (PONs) proved itself as a front-runner technique, which started from a simple and low cost architecture of single wayelength transmission on fiber with Time Division Multiplexing (TDM) based ONUs sharing. However, there are several challenges in TDM-PON, such as high splitter loss, limited number of optical network units (ONUs), aggregated bandwidth of system, acceptable power budget and restricted transmission reach. To resolve these issues, Wavelength Division Multiplexing (WDM) based passive optical networks are proposed. But for further improvement there is a need to mitigate the more bottlenecks such as design complexities, low extinction ratio, poor receiver sensitivity, high deployment cost, less spectrally-efficient design and lack of effective bandwidth utilization and wavelength sharing in WDM-PON.This dissertation covers the comprehensive and concrete research work with theoretical and analytical analysis of challenges in WDM-PON. In which, we proposed DQPSK and IRZ as robust advanced modulation formats, single fiber bidirectional architecture for cost-effectiveness, reduced channel spacing in spectrally-efficient design and hybrid WDM/TDM-PON for effective bandwidth utilization and wavelength sharing. Hence, in the thesis "Implementation of robust advanced modulation formats for cost-effective high capacity PON", following are the key innovations and contributions:Firstly, to resolve the problems of degradation of transmission quality, limitation of high data rate and sufficient transmission reach in passive optical networks (PONs), implementation of robust advanced modulation formats have been proposed innovatively in a combination of differential quadrature phase shift keying (DQPSK) in downstream and re-modulated inverse return-to-zero (IRZ) in upstream, to achieve better extinction ratio, high data rate and improved receiver sensitivity. Transmission performance has been analyzed by the simulation in Optisystem7.0, in which good symbols instance in constellation diagrams, clear eye diagrams and low transmission power penalties ensure that proposed design has good tolerance against transmission impairments.Secondly, high cost design is a big challenge in WDM-PON deployment. Therefore, in this thesis a cost-effective intensity re-modulation based centralized light source WDM-PON technique has been proposed with implementation of robust advanced modulation formats without pulse carving, dispersion compensation fiber (DCF) and erbium doped fiber amplifier (EDFA) in both direction of transmission. The deployment cost has been further reduced by employing single fiber bidirectional transmission after carefully considering the backscattering noise-resilience. The simulation results verify that proposed cost-effective WDM-PON can successfully be transmitted over a distance of20to25km with low transmission power penalties.Thirdly, explosive growth in high bandwidth demands in past few years is a most critical issue. The high capacity can be achieved by either increasing the data rate of wavelength channels or by reducing channel spacing between adjacent wavelengths to add more wavelengths channels. Therefore, another important contribution in this dissertation is the successful research towards the spectrally-efficient WDM-PON design. In which, instead of previous100GHz channel spacing,50GHz channel spacing has been employed for16channels in both direction of proposed WDM-PON. The simulation based transmission performance has been analyzed which validates the feasibility with smaller transmission penalties and resistance against transmission noise.Fourthly, how to utilize the bandwidth efficiently? It is another very important matter of concern and this can be achieved by sharing of wavelength among ONUs via TDM technique. Therefore, an innovative work is contributed by implementation of spectrally-efficient design in hybrid WDM/TDM-PON, including the potential advantages of both the WDM and the TDM techniques. The proposed design can support256ONUs having data rate up to625Mbit/s in downstream and also up to156Mbit/s in upstream for every subscriber. Further, negligible transmission power penalties have been found in the simulation results which reflect good transmission performance.Hence, this research dissertation, about implementation of robust advanced modulation formats in cost-effective high capacity PON, provides a foundation for future research work to achieve simple, cost-effective, spectrally-efficient design for the high capacity next generation access networks.更多还原