灵活透明光网络中自适应传输机理和关键技术研究

【作者】 张华；

【导师】 顾畹仪；

【作者基本信息】 北京邮电大学 ， 电磁场与微波技术， 2008， 博士

【摘要】 灵活透明光网络是传送网发展演进的重要方向,为网络的运营维护提供了诸多便利。比如,利用通用多协议标签交换(GMPLS)技术可以构造分布式的智能控制平面,实现对连接的快速建立与拆除,支持动态灵活的业务配置以及高效率的资源优化。另外随着各种具有全光处理能力的光器件(如光子交叉连接器、可调全光波长转换器等)技术的逐步成熟,为光信号在全网中透明传输提供了可能性,同时也减少了网络铺设中采用的昂贵光电光转换设备的数量,极大降低了网络建设和运营成本。但是光网络的灵活性和透明性也带来了很多问题,主要是由于缺乏光域3R再生功能,光信号在传输中的物理损伤会产生累积。随着向网状拓扑的演变,光网络的灵活性进一步增强,传输路径的改变将导致物理损伤的动态变化,这些损伤积累的影响有可能造成信号的传输质量劣化甚至不满足系统传输要求。尽管已经推出各种具有自适应补偿能力的器件来解决这一问题,但这些器件目前还都只是传送平面上的局部自适应调节,不了解相互之间的补偿状态,缺乏协同工作能力,从而造成不必要的运营维护开销。因此本论文在国家863项目的支持下,针对上述问题进行了深入研究,获得了若干具有创新性的成果,已经或将要发表在美国光学学会期刊Optics Express和Journal of Optical Networking上。主要的工作和创新点包括以下几个方面:第一,针对光网络中灵活透明性所带来的物理损伤动态变化问题,并且为了充分利用网络中各种可调节设备(如可调色散补偿器、变增益光放大器等)的物理损伤补偿能力,在灵活透明光网络领域首次提出了支持端到端动态传输质量优化的自适应传输思想,通过在现有ASON架构基础上加入对传送平面物理特性控制的能力,实现动态的从源端到目的端的整个光路传输质量的调节和改善。第二,基于现有ASON控制平面功能架构,设计出了支持自适应传输功能的自适应控制面结构,新增了“物理信息采集”、“传输性能评估”、“补偿预算计算”及“传输性能控制”等四个功能模块,从而实现了对链路中各可调节物理损伤补偿器件的动态端到端性能调节,同时也降低了系统调节开销。第三,针对自适应传输所面临的关键问题,提出了初步可行的解决方案,主要包括:1)扩展现有的GMPLS信令协议使其能够支持对物理器件参数的收集以及对性能优化参数的传递;2)参考ITU-T的G680标准以及其它的研究成果,给出了对通路残余色散、接收端光信噪比以及累积非线性效应的评估方法;3)创建了自适应传输所遵循的优化模型并初步设计了可行的启发式优化算法。第四,基于光子晶体光纤中光脉冲传输的物理模型自主开发了模拟超短脉冲在光子晶体光纤中传输的计算机仿真程序,并基于此工具首次开展了在具有双零色散波长的光子晶体光纤中初始脉冲频率啁啾对超连续谱产生的影响研究,分析了正啁啾和负啁啾在超连续谱产生中的不同作用,研究结果表明,正啁啾脉冲可以产生规则的频谱,而负啁啾脉冲则产生复杂不规则的频谱,很难在实际中应用。此外,正啁啾还极大增强了四波混频的效率,通过选择合适的正啁啾值,几乎所有的脉冲能量都可以从反常色散区完全转移到正常色散区。相关的研究成果可对灵活透明光网络中实现可调全光波长转换以及参量放大起到理论指导作用。更多还原

【Abstract】 Agile and transparent optical network is the important evolution direction of optical transport network and the agility and transparency are convenient to operate and manage the network. For example, the distributed intelligent control plane can be constructed by generalized multi-protocol label switching (GMPLS), and the fast connection setup and remove can be realized. Then this can support dynamic service configuration and efficient resource optimization. Moreover, all kinks of transparent optical components, such as photonic cross connector and tunable all-optical wavelength converter, have been commercialized. This can support all-optical signal transmission and reduce the quantity of expensive optical-electrical-optical conversion devices and decrease CAPEX and OPEX.However, the agility and transparency also bring some problems because the physical impairments will be cumulated without optical 3R regeneration. The network agility will be enhanced as the topology evolves to mesh, and the lightpath change will result in dynamic change of the cumulative physical impairments. Then this may cause the signal degradation or even transmission requirements cannot be satisfied. Although some adaptive impairment compensators have been developed to resolve this problem, these components only realize local adaptive adjustment. They cannot understand the compensation states of each other and lack the team-working ability. Then this would result in unnecessary overhead. Therefore the above problems are investigated in depth with the support of the Hi-Tech Research and Development Program of China, and the research results have or will be published in Optics Express and Journal of Optical Networking. The main innovative results are listed as follows.Firstly, for the sake of solving the above problems and making the best of the compensation capability of various tunable devices, we proposed the thought of adaptive transmission in agile and transparent optical networks for the first time, which can support dynamic end-to-end optimization for quality of transmission. The global transmission quality from source to destination can be adjusted and improved dynamically through adding the capacity of controlling physical characteristics of transport plane into ASON.Secondly, based on the current control plane in ASON, we designed the architecture of adaptive control plane which can support adaptive transmission. And the new four function modules, namely information collection module, performance estimation module, compensation budget computing module, and performance control module, had been added. Then the dynamic end-to-end adjustment can be achieved and the system overhead will be decreased.Thirdly, we proposed the preliminary solutions to the key problems caused by adaptive transmission which mainly included 1) the extension of GMPLS signaling protocol to support the collection of physical parameters and the delivery of optimization parameters; 2) the fast estimation methods of transmission performance including the residual path dispersion, the received OSNR and the cumulative nonlinear phase shift; 3) the optimization model creation and the feasible heuristic algorithms design.Finally, based on the physical model of optical pulses propagation in photonic crystal fibers (PCFs), we had independently developed the computer program which can simulate the process of ultra-short pulses propagation in PCFs. Based on this tool, the effect of initial frequency chirp on supercontinuum generation (SCG) is investigated numerically in PCFs with two zero-dispersion wavelengths for the first time. The positive chirps, instead of zero or negative chirps, are recommended because self phase modulation and four-wave mixing can be facilitated by employing positive chirps. In contrast with the complicated and irregular spectrum generated by negative-chirped pulse, the spectrums generated by positive-chirped pulses are wider and much more regular. Moreover, the efficiency of frequency conversion is also improved because of initial positive chirps. Nearly all the energy between the zero-dispersion wavelengths can be transferred to the normal dispersion region provided that the initial positive chirp is large enough. This property has important potential applications in tunable all optical wavelength conversion and broadband parametric amplification.更多还原