Elimination of All-Optical Cycles in Wavelength-Routed Optical Wide Area Networks

透明（广域）波长路由光网络可以通过使用由光纤连接在一起的波长交叉连接交换机来创建，以形成任意的网状结构。 通过连接到某些交叉连接的电子站进入网络。 这种波长路由的光网络正在研究和演示的一部分，ARPA赞助的计划在贝尔核心（ONT和MONET）。 波长交叉连接开关可以使用声光滤波器（AOTF）或基于WDM复用器/解复用器的技术来实现。 波长交叉连接在功能上可以包括或可以不包括波长转换。 这些波长交叉连接交换机具有这样的特性，即它们可以将自己配置成未指定的状态。 交换机的每个输入端口总是连接到交换机的某个输出端口，而不管这种连接对于信息传送是否是必需的。 由于这些未指定状态的存在，存在在网络中建立非预期的全光循环的可能性（即，其中没有终端电子设备的环路）。 如果这样的循环包含放大器（例如，在掺铒光纤放大器（EDFA）中，存在净环路增益大于环路损耗的可能性。 来自放大器的放大的自发辐射（ASE）噪声可以在这样的反馈回路中积累以使放大器饱和并且导致回路中的ASE噪声的振荡。 为了使网络执行任何有用的操作，必须从光网络中消除如上定义的这种全光（并且在下文中称为“白色”循环）。 此外，对于波长交叉连接导致信号串扰的实际情况，存在具有振荡串扰信号的闭合周期的可能性。 我们将研究这个问题的网络路由层和物理层解决方案。 在网络路由层，我们将研究算法，建立新的透明的光连接的请求，避免在网络中创建这样的周期。 这些算法将尝试为连接找到路由，然后（以后处理方式）配置交换机，以便可能创建的白色周期将自动消除。 此外，对于更现实的情况下，其中的交叉连接导致串扰，我们提出了呼叫建立算法，最大限度地减少串扰周期的可能性。 在物理层，我们将研究透明波长路由光网络中出现的各种与设备相关的问题。 物理层的研究将直接影响到上述网络路由层的工作。 具体地说，我们建议（1）提供器件表征和可用的计算机模型，目前和未来的光学器件，如光放大器，光波长交叉连接开关（具有和不具有波长转换）和光纤链路，包括网络理论家的连接器模型，使得“理想”网络模型可以升级为“现实”网络模型;（2）就网络示范及网络分析所发现的问题，探讨在物理层的潜在解决方案;及（3）找出可行的替代光学装置，特别是放大器及开关，其物理特性将直接有利于透明光学网络的实施。 我们将反馈这项工作的结果，以便使ARPA赞助的ONT（Bellcore，BNR/NT，哥伦比亚大学，休斯，LLNL，罗克韦尔，UTRC）和MONET（AT T，Bellcore，Pacific Telesis，Bell Atlantic，Bellsouth）财团直接受益。 ***

9521249 Mukherjee A transparent (wide-area) wavelength-routed optical network may be created by using wavelength cross-connect switches connected together by fiber to from an arbitrary mesh structure. The network is accessed through electronic stations that are attached to some of these cross-connects. Such a wavelength-routed optical network is being studied and demonstrated as a part of ARPA-sponsored programs at Bellcore (ONTC and MONET). The wavelength cross-connect switches may be implemented using acousto-optic filters (AOTFs) or WDM multiplexer/demultiplexer-based technologies. The wavelength cross-connects may or may not include a wavelength-translation functionally. These wavelength cross-connect switches have the property that they may configure themselves into unspecified states. Each input port of a switch is always connected to some output port of the switch whether or not such a connection is required for the purpose of information transfer. Due to the presence of these unspecified states, there exists the possibility of setting up unintended all-optical cycles in the network (viz. a loop with no terminating electronics in it). IF such a cycle contains amplifiers (e.g., Erbium-Doped Fiber Amplifiers (EDFAs), there is a possibility that the net loop gain is greater than the loop loss. The amplified spontaneous emission (ASE) noise from amplifiers can build up in such a feedback loop to saturate the amplifiers and result in oscillations of the ASE noise in the loop. Such all-optical as defined above (and hereafter referred to as "white" cycles) must be eliminated from an optical network in order for the network to perform any useful operation. Furthermore, for the realistic case in which the wavelength cross-connects result in signal cross-talk, there is a possibility of having closed cycles with oscillating cross-talk signals. We will investigate both the network-routing layer and the physical layer solutions to this problem. At the network-routing layer, , w e will examine algorithms that set up new transparent optical connections upon request avoiding the creation of such cycles in the network. These algorithms will attempt to find a route for a connection and then (in a post-processing fashion) configure switches such that white cycles that might get created would automatically get eliminated. Furthermore, for the more realistic case in which the cross-connects result in cross-talk, we propose call-set-up algorithms that minimize the possibility of cross-talk cycles. At the physical layer, we will study various device-related issues that arise in transparent wavelength-routed optical networks. The physical layer study will directly influence the network-routing layer work stated above. Specifically, we propose (1) to provide device characterization and usable computer models of present and future optical devices such as optical amplifiers, optical wavelength cross-connect switches (with and without wavelength translation), and fiber links including connector models to network theorist so that "ideal" network models may be upgraded to "realistic" network models; (2) to explore potential solutions in the physical layer to problems identified by network demonstrations and network analysis; and (3) to identify viable alternative optical devices, particularly amplifiers and switches, whose physical properties will directly benefit the implementation of transparent optical networks. We will feed back the results of this work so as to directly benefit the ARPA-sponsored ONTC (Bellcore, BNR/NT, Columbia University, Hughes, LLNL, Rockwell, UTRC) and MONET (AT&T, Bellcore, Pacific Telesis, Bell Atlantic, Bellsouth) consortia. ***