Design of Translucent Optical WDM Networks

网络用户数量的空前增长和高带宽终端用户应用的出现给下一代计算机网络的体系结构设计带来了新的挑战。 采用波分复用（WDM）的光网络通过利用光纤的巨大容量来超越电子网络的带宽限制。 虽然这种技术看起来非常有前途，但未来这种光网络的大规模部署取决于通信网络需求和物理网络现实的快速融合。 光网络拟议研究的重点是通过解决几个系统级挑战，同时承认现有设备的局限性，来促进这一过程。 目前，在现有和新的光纤基础设施上正在部署大量千兆位/秒通道的波分复用，以应对本地和长途数字流量的爆炸性增长。 WDM部署正在激增，因为可以通过激活现有光纤设备上的额外波长信道来经济地提供容量。 然而，随着光纤容量的增长，对网络节点和接入点处的昂贵电子交换机的容量施加了越来越大的压力。 可重新配置的透明光网络试图通过确保信号仅在源和目的地离开光域来提供低成本的替代方案，从而避免不必要的光电转换。 然而，存在由物理层损伤施加的基本限制，其限制透明光网络中的端到端连接的长度。 跨越多个节点和长距离的连接可能会累积由基本物理约束（例如光纤色散和非线性、自发发射噪声和设备缺陷（例如串扰））施加的严重损伤。 由于点对点通信性能的物理特性在实验和理论上都得到了很好的理解，因此有人认为，国家级网络将通过在每个节点部署具有电子再生的点对点WDM来避免物理层损害。 这种网络称为不透明光网络。 与点对点链路和物理层光器件的情况不同，复杂的全光或光电混合网络的分析和仿真仍处于起步阶段，经过充分测试的工具现在才被开发出来。 该项目的目标是提出，评估和研究下一代高带宽基于WDM的光网络的设计，这是兼容的光器件的物理层特性。 特别是，研究人员计划调查以下研究主题： 稀疏再生和透明光网络：关于（国家规模）光波分复用（WDM）网络中的透明性与不透明性，已经有大量的讨论[11]。 在[22]中，研究人员引入了半透明光网络的概念-一种支持网络内光信号选择性再生的网络。 研究人员的研究表明，对于中等规模的网络，不连续性有助于提高网络的整体性能。 对于较大规模的网络，光纤非线性和色散引入的损伤不可忽略，研究人员预计可能需要更高程度的不透明度来对抗信号退化，但这是一个有待进一步研究的开放问题。 研究人员还计划在全国范围的WDM网络中的选定位置调查一些信号再生器的效果。 考虑功率因素的路由和波长分配：路由和波长分配（RWA）是波分复用（WDM）光网络中出现的一个重要问题。 以前的研究已经解决了这个问题的假设下，完美的条件下，关于信号的功率的许多变化。 研究人员建议调查这个问题，同时允许路由信号的组件，如抽头，多路复用器，开关元件，光纤链路等的研究人员计划，包括新的放大器和其他设备模型，以表征网络的性能退化。

The unprecedented growth in the number of networked users and the emergence of high-bandwidth end-user applications impose new challenges in the design of architectures for next-generation computer networks. Optical networks, employing Wavelength Division Multiplexing (WDM), transcend the bandwidth limitations of electronic networks by utilizing the enormous capacity of the optical fiber. Though this technology looks extremely promising, large-scale deployment of such optical networks in the future depends on a rapid convergence of communication network requirements and physical network realities. The focus of the proposed research in optical networks is to facilitate this process, by tackling several system-level challenges while acknowledging the limitations of existing devices. Wavelength Division Multiplexing of numerous multi-gigabit/sec channels is being deployed right now on existing and new fiber infrastructure in respones to explosive growth in both local and long-haul digital traffic. WDM deployment is surging because capacity may be economically provisioned by activating additional wavelength channels on existing fiber plant. However, as the fiber capacity grows, increasing strain is placed on the capacity of costly electronic switches at network nodes and access points. A reconfigurable transparent optical network seeks to provide a low-cost alternative by ensuring that the signal leaves the optical domain only at the source and destination, thereby avoiding unnecessary opto-electronic conversion. There are, however, fundamental limits imposed by physical-layer impairments that limit the length of end-to-end connections in transparent optical networks. Connections that span several nodes and large distances may acumulate severe impairments imposed by fundametal physical constraints such as fiber dispersion and nonlinearties, spontaneous emission noise, and device imperfections such as crosstalk. Since the physics of point-to-point communications performance is well understood experimentally and theoretically, it has been argued that nation-scale networks will avoid physical-layer impairments by deploying point-to-point WDM with electronic regeneration at each node. Such a network is called an opaque optical network. Unlike the case of point-to-point links and physical-layer optical devices, the analysis and simulation of complex all-optical or hybrid optical-electronic networks is still in its infancy and well-tested tools are only now being developed. The goals of this project are to propose, evaluate and study designs for the next-generation high-bandwidth WDM-based optical networks, which are compatible with the physical-layer characteristics of optical devices. In particular, the researcher plans to investigate the following research topics: Sparse Regeneration and Translucent Optical Networks: There has been a great deal of discussion regarding transparency vs. opacity in (national-scale) optical wavelength devision multiplexed (WDM) networks [11]. In [22], the researcher introduced the notion of a translucent optical network - a network which supports selective regeneration of optical signals within the network. The researcher's study showed that, for medium-scale networks translucency can help to improve the overall network performance. For larger-scale networks, where impairments introduced by fiber nonlinearities and dispersion cannot be ignored, the researcher anticipates that a higher degree of opacity may be needed to combat signal degradations, but this is an open problem for further research. The researcher also plans to investigate the effect of a few signal regenerators at select locations in a nation-wide WDM network. Routing and Wavelength Assignment with Power Considerations: Routing and wavelength assignment (RWA) is an important problem that arises in wavelength division multiplexed (WDM) optical networks. Previous studies have solved many variations of this problem under the assumption of perfect conditions regarding the power of a signal. The researcher propose to investigate this problem while allowing for degradation of routed signals by components such as taps, multiplexers, switching elements, fiber links, etc. The researcher plans to include novel amplifier and other device models to characterize the performance of the networks.