Optical Packet Switch Architectures: A Comparative Analysis for Bursty Traffic and Optical Cost

Abstract

In this article, we present the comparative analysis of various optical packet switch architectures. The comparison is done on the basis of bursty traffic arrival and the optical cost of various optical components used to build that switch. The architectures chosen for the analysis were previously proposed by us and their performance was evaluated only for the uniform random traffic arrival. Hence, this article can be considered as the cumulative and effective extension of the previous works. The computer simulations are performed to obtain the packet loss probability and average delay in presence of bursty traffic.     

Design and Performance Evaluation of Optical Ethernet Switching Architecture with Liquid Crystal on Silicon-Based Beam-Steering Technology

A non-blocking optical Ethernet switching architecture with liquid crystal on a silicon-based beam-steering switch and optical output buffer strategies are proposed. For preserving service packet sequencing and fairness of routing sequence, priority and round-robin algorithms are adopted at the optical output buffer in this research. Four methods were used to implement tunable fiber delay modules for the optical output buffers to handle Ethernet packets with variable bit-rates. The results reported are based on the simulations performed to evaluate the proposed switching architecture with traffic analysis under a traffic model captured from a real-core network.     

波长转换器和光纤延迟线在WDM光分组交换中的结构设计和性能研究

介绍了两种新颖的光分组交换结构——MOD1和MOD2,用于解决分组冲突问题.其特点在于,MOD1共享了一组非简并的延迟线,而MOD2则是共享了一组简并的延迟线和波长转换器.研究表明,对于非突发业务,两种结构都只需要少量的延迟线即可获得理想的性能.此时,MOD1比MOD2更加能降低系统体积和成本.而对于突发业务,如果MOD1所共享的延迟线数量和MOD2所共享的延迟线和转换器的总数量相等,MOD2的分组丢弃率要远远低于MOD1.随着业务突发程度的增加,MOD2中的转换器数量也需要增加才能维持给定的分组丢弃率,但即使业务突发程度很高,MOD2在体积、成本和性能等三方面均可取得较理想的折衷.     

光纤延迟线和可调谐波长转换器在光分组交换网络竞争解决结构中的性能分析

研究了光分组交换网络中的两种竞争解决方案.结合课题研究的进展,基于突发和非突发业务,对这两种竞争处理结构进行了深入分析,得出了几点重要结论,首先,在竞争处理上,对于非突发业务,光纤延迟线比可调谐波长转换器有效;而对于突发业务而言,可调谐波长转换器比光纤延迟线有效.其次,在突发业务下反馈式光纤延迟线结构（FFA）是一种较为理想的竞争解决结构,但对非突发业务而言,反馈式光纤延迟线和可调谐波长转换器结构（FFTA）在成本上和结构尺寸上比FFA要有效的多.随着平均突发长度的增加,FFTA中的可调谐波长转换器数目也要增加才能获得合理的分组丢失率。但无论是针对突发业务还是非突发业务,FFTA都是一种成本有效的竞争解决结构.     

针对WWW业务的光缓存优化设计

研究了异步光分组网中的输出光缓存问题，与以往不同的是在处理光分组到达时间间隔时采用Weibull分布，以便更有效地描述互联网中的WWW业务流量类型．通过建立基于Weibull分布的排队模型，得到了排队模型中的丢包率的解析式，并根据数值解得出了光缓存系统的丢包率、系统实际利用率、服务窗口利用率以及平均排队时间随光纤延时线单位缓存时间变化的关系曲线．研究结果表明：在不同的业务强度和缓存深度下选取恰当的单位缓存时间，可以优化光缓存系统的性能．     

Performance analysis of optical burst switching under bursty traffic

The performance of the algorithm of the data channel scheduling algorithm of latest available unscheduled channel with void filling (LAUC-VF) under bursty traffic is presented firstly. A bursty traffic model for optical burst switch performance simulation is also introduced.     

ATMOS (ATM optical switching)—system perspective

The expected traffic growth from new broadband services will require network capacities that can be beneficially provided by optical WDM transport networks. Optical packet techniques are essential for large networks to provide flexibility and granularity. A layered network architecture with a transparent optical layer and optical packet layers has been elaborated. Four switching concept options for large optical ATM switch fabrics in the public network and small access nodes are presented. The technology for the related key functions of space and wavelength switching was developed in the RACE ATMOS project and the feasibility of concepts and technologies was verified in four system demonstrators.     

全混洗交换Omega互连网络的光学实现

本文提出了一种由左、右全混洗和空间光开关列阵组成的等效Omega网络;成功地设计了一种实现全混洗互连的低损耗,等程的光学组合棱镜.由两块光学组合棱镜和空间光开关列阵组合成的光学系统实现了全混洗交换光学互连网络,该光学互连网络已在实验中得到了证实.     

High-Speed Optical Packet Switch with an Optical Digital-to-Analog Conversion-Type Header Processor

We describe a novel type of an optical packet switch with an optical header processor based on optical signal processing and wavelength routing architecture. It consists of an optical digital-to-analog conversion-type header processor, wavelength selection portion with an electrically tunable laser, a wavelength converter based on a semiconductor optical amplifier (SOA), and wavelength routing by use of an arrayed waveguide grating (AWG), which is called a wavelength label switch (WLS). Wavelength switching of an electrically tunable laser, and wavelength conversion were successfully achieved within a few nanoseconds after recognition of an optical header using a two-bit optical header processor and a FPGA-based wavelength table. High-speed transfer performance of less than a few tens of nanoseconds and BER of less than 10^-10 were verified in the wavelength routing operation among three assigned wavelengths.     

MEMS与MEMS光开关

微机电系统(MEMS)技术是一种新型制造技术,在光通信的发展中得到广泛的应用,有极大的市场价值.在整个光通信中,光开关是较为重要的光无源器件,在光网络系统中可对光信号进行选择性操作.随着光通信的日益发展,对光开关的技术要求也日益提高,利用MEMS技术制作的新型光开关具有体积小、重量轻、能耗低、集成化程度高等特点,从而日益成为研究的热点.本文简单介绍了MEMS技术和其主要特点,并较详细地阐述了MEMS技术在光通信中的应用,以及MEMS光开关的结构、发展趋势和目前存在的主要问题.     

Optical Packet Routing Performance of an Optical Packet Switch Digital/ Analog-Conversion-Type With an Optical Header Processor (Wavelength Label Switch)

We demonstrate the routing operation of optical packets by an optical packet switch consisting of an optical digital-to-analog conversion-type header processor, a wavelength converter using an electrically-tunable laser, and an arrayed-waveguide grating router. A packet transfer by two -bit optical header was achieved for the first time.     

光互连网络中四功能交换开关研究

由节点开关单元按照一定的连接规则所构成的光互连网络,在全光通信和光信息处理中具有重要的应用。基于节点开关一般实现光信号的直通和交换功能的特点,利用成熟的偏振光控制技术,通过位相型空间光调制器对信号光偏振态的控制,完成信号的路由和开关动作,从而设计出具有直通、交换、上播和下播功能的节点交换开关。与传统设计思想相比,该方法不仅能够充分利用信号光的能量,有效的减少光能量的损耗,而且还具有与偏振无关等特点。该四功能交换开关,对于优化和拓展光互连网络的结构和功能具有一定的意义。     

光分组组装机制对自相似流的整形效应分析

通过系统仿真和数值分析，全面地分析了光分组交换网中分组组装机制对自相似流的整形效应，结果表明：光分组组装机制通过改善流量的关键特性，包括：自相似性、短程相关性和边缘分布，来实现自相似流量整形. 而且，业务强度越小、光分组组装门限越大、组装计时间隔越小，光分组组装机制对自相似流的整形效果越好.     

The Impact of Signal Properties with Unbalanced Traffic on SOA Switches in Optical Packet Switched Networks

In this paper, we present the property evaluated modeling of switching matrix based on the XGM in SOA for optical packet-switched networks. Crosstalk-induced bit error rate (BER), packet error rate (PER), the dimension of the switching node and cascaded capacity under unbalanced traffic are examined, which proves to be relevant to the peculiarities of signal pulse such as initial chirp, shape and bit rate.Several rules are drawn to facilitate the design of SOA-based switching matrix under unbalanced traffic.     

适用于光突发交换网的可编程光缓存器

提出了两种适用于光突发交换网的可编程光缓存器结构：交叉型和多端口开关型.两种结构都能满足突发包缓存的超长性和可变性的要求，且结构简单紧凑，成本低，可扩展.交叉型缓存器通过指定信号在每个子缓存模块的光纤环中的循环次数即能实现可变时间的延迟.多端口开关型缓存器通过指定信号在两个多端口开关相应端口与所接光纤延迟线组成的光纤环中的循环次数实现可变时间的延迟.仿真结果表明，两种可编程光缓存器都能对光突发包实现ns级指定时间延迟，可用于解决光突发交换网突发包的冲突问题.     

A Multiservice Voice, Data, and Video Network Enabled by Optical Ethernet

With data now approaching 60% of all aggregate traffic and expected to grow to 90% of all traffic by 2004, networks designed around all-packet architectures are being envisioned. Within this timeframe, a network vision is to deliver voice, video, and data services over a single packet-oriented network. Some entrepreneurial network providers are pursuing this vision in an even earlier timeframe.

This article introduces a multiservices voice, data, and multicast video network over an Optical Ethernet architecture for residents of multidwelling units (MDU). This article reviews the network architecture for delivering these services over Optical Ethernet and addresses the challenges of handling service types with different bandwidths and latencies over a common packet-oriented infrastructure. As an example, it addresses the challenge of managing latency-intolerant traffic such as voice over IP over a common architecture as Internet data. Furthermore, it discusses the challenges of delivering over 100 channels of broadcast video as well as video on demand over the same infrastructure.     

基于最小化平均分组跳的分组交换多跳光网的设计

本文研究了支持分组交换通信的波长路由光网的逻辑拓扑设计问题,并将它表示为混合整数线性规划问题(MILP),其目标函数为最小化平均分组跳数目.在约束条件中同时考虑了分组传输时延和排队时延.我们以6结点的网络为例,对于不同的收发机数目和时延边界,数值结果表明最小化平均分组跳数目等价于最小化网络拥塞.小的平均分组跳数目可以保证网络通信时具有较小的时延.最后,对于不同的通信模式,我们比较分析了网格的优化性能参数,这些结果有助于提出更好的启发式算法.     

Modeling and design of WDM optical buffers in asynchronous and variable-length optical packet switches

This paper aims to analyze the influence of wavelength conversion on the design of optical fiber delay line (FDL) buffers in a wavelength-division multiplexing (WDM) packet switch. We focus on the network scenario that variable-length packets arrive at the optical switch asynchronously. Through a detailed analysis of the behaviors of packets in the WDM FDL buffer, an approximate analytical traffic model is established. And the theoretical model is proved to be reasonable by simulations. Based on the model, it is clear that, under the same traffic load per wavelength channel, the utilization of tunable wavelength converters (TWCs) to resolve the output contention significantly reduces the number of fiber delay lines (FDLs) in optical buffers, and to achieve a given packet loss probability under a certain number of FDLs, the required number of tunable wavelengths can be predicted. The model can also estimate the optimal value of the basic time unit of the FDLs, and examine the influence of WDM on the optimal value. Finally, the impact of wavelength conversion on the optical switch size is analyzed. To the best of our knowledge, it is the first time that modeling on this problem is presented.     

基于半导体光放大器进行光标签提取的性能分析

利用半导体光放大器增益饱和数学模型,第一次分析了基于单个半导体放大器进行光标签提取的节点性能.通过对半导体光放大器的参量分析和优化,仿真显示,对于标签速率2.5 Gb/ s 、净荷速率40 Gb/s 的光分组包,提取的标签消光比可达到13 dB.     

Cutting-Edge Technologies on Broadband and Scalable Photonic-Network—Packet switched networks based on all-optical label processing—

Ultra-high speed all-optical label processing methods are proposed and experimentally demonstrated. These methods dramatically increase the label processing capability. Optical packet switch (OPS) systems and networks based on OPS nodes are expressed as an application of optical processing technologies. First, the 40 Gbit/s/port OPS prototype with all-optical label processor, optical switch, optical buffer, and electronic scheduler is described. The feasibility of OPS networks is verified by experimental demonstrations.