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

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.     

Feed-Forward- and Shared-Buffer-Based Optical Packet Switch Architecture

Abstract

This architecture incorporates wavelength-routed loop-buffer modules in the feed-forward configuration, and the buffering in these modules is recirculating in nature, using shared memory. The signal quality will deteriorate during each revolution, due to the insertion loss of the various optical components; therefore, it will impose a limit on the number of circulations that a packet can take in the buffer before its correct reception. Generally, this limit has not been considered in the past, but one should have to take care of it in the current scenario for the actual switching systems.     

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．     

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.     

Advanced Optical Network

The following article describes an advanced dense wavelength division multiplexing (DWDM) Optical Network developed by L-3 Photonics. The network, configured as an amplified optical bus, carries traffic simultaneously in both directions, using multiple wavelengths. As a result, data distribution is of the form peer-to-multi-peer, it is protocol independent, and it is scalable. The network leverages the rapid growth in commercial optical technologies, including wavelength division multiplexing (WDM), and when applied to military and commercial platforms such as aircraft, ships, unmanned and other vehicles, provides a cost-effective, low-weight, high-speed, and high noise-immune data distribution system.     

Integrated Contention Resolution and Control Algorithm for Optical Burst Switched Networks

Abstract

This article compares the conventional and proposed integrated contention resolution and control algorithm in optical burst switching with respect to burst loss probability and network throughput. Results have shown that the proposed approach behaves well in practice and responds quickly to any change in network status, while improving the overall network performance. It is shown that the proposed algorithm (ICRCA) not only provides significantly better burst loss performance than the conventional algorithms, but is also void of any packet re-orderings.     

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.     

Optical Communications Research Activities at COM RD1 Siemens S.A.

Abstract

This article summarizes the research activities carried out by the R&D Optical Networks Communications group (COM RD1), at Siemens S.A., in collaboration with both universities and other research institutes. These activities cover various aspects of advanced modulation formats, all optical wavelength conversion, optical quality of signal monitoring in transparent WDM networks, routing, and wavelength assignment in optical networks.     

Optical Communications Research at Institute of Telecommunications

Abstract

In this contribution we present a brief summary of research activities carried out at Instituto de Telecomunicações (IT, Institute of Telecommunications) in optical communications. These activities cover various aspects related with optical components/subsystems, optical communication systems, and optical networking.     

Performance of Optical OFDM Receiver in the Presence of System Impairments

Abstract

Recently, there is an increasing interest in using orthogonal frequency division multiplexing schemes in advanced optical communication systems to compensate fiber dispersion. This article presents a comprehensive theoretical analysis to treat the optical orthogonal frequency division multiplexing scheme as a special case of optical subcarrier multiplexing system. An analytical expression is derived to calculate the laser power required to achieve a specific level of signal-to-noise ratio, as a function of various system and noise parameters. Simulations show that the presence of laser relative intensity noise may cause a signal-to-noise ratio floor, where the bit error rate cannot be improved further even when the laser power increases dramatically.     

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.     

Energy-Efficient Next-Generation Passive Optical Networks Based on Sleep Mode and Heuristic Optimization

Abstract

In this article, an energy-efficiency mechanism for next-generation passive optical networks is investigated through heuristic particle swarm optimization. Ten-gigabit Ethernet–wavelength division multiplexing optical code division multiplexing–passive optical network next-generation passive optical networks are based on the use of a legacy 10-gigabit Ethernet–passive optical network with the advantage of using only an en/decoder pair of optical code division multiplexing technology, thus eliminating the en/decoder at each optical network unit. The proposed joint mechanism is based on the sleep-mode power-saving scheme for a 10-gigabit Ethernet–passive optical network, combined with a power control procedure aiming to adjust the transmitted power of the active optical network units while maximizing the overall energy-efficiency network. The particle swarm optimization based power control algorithm establishes the optimal transmitted power in each optical network unit according to the network pre-defined quality of service requirements. The objective is controlling the power consumption of the optical network unit according to the traffic demand by adjusting its transmitter power in an attempt to maximize the number of transmitted bits with minimum energy consumption, achieving maximal system energy efficiency. Numerical results have revealed that it is possible to save 75% of energy consumption with the proposed particle swarm optimization based sleep-mode energy-efficiency mechanism compared to 55% energy savings when just a sleeping-mode-based mechanism is deployed.     

Hybrid buffering architecture for packet contention resolution of an optical packet switch

Packet contention is a major issue in optical packet switching network and it is not a trivial task to resolve due to lack of optical RAM technology. In order to resolve contention optical buffering approach is used using fiber delay lines (FDLs). Yet there is a heavy packet loss rate due to unavailability of output port and free FDLs. This paper proposes a hybrid buffering architecture using feed-forward and feedback shared FLDs to resolve packet contention resolution of an optical packet switch. Feed-forward FDLs are used as primary buffer and feedback FDLs are implemented as supplementary buffer. Simulation result shows that proposed hybrid buffering switch achieves packet loss rate between 10⁻¹ and 10⁻² at heavy traffic load (ρ = 0.9) for a 32 × 32 switch using different FDL length.     

A Techno-Economic Study on the Outside Plant Cost of Current and Next-Generation Fiber-to-the-X Deployments

Abstract

A techno-economic study on the outside plant costs of fiber-to-the-X infrastructures is presented in this article. Standardized passive optical network and active optical network technologies, implemented in fiber-to-the-home architectures, are presented/compared in terms of costs. Future architectures based on passive optical networks are investigated, their outside plant infrastructure, and corresponding costs are reviewed. Cost comparisons of fiber-to-the-X infrastructures reveal significant differences. Besides fiber-to-the-node being the less costly, it is shown that the cost of high splitting ratio passive optical network fiber-to-the-home infrastructures is not increasing linearly with the splitting ratio. The highest splitting ratio is not always the one with the largest savings percentage. Referring to current and future fiber-to-the-home access network architectures/technologies, the flexibility of wavelength division multiplexing/time division multiplexing passive optical networks is estimated to reach a 40% reduction in outside plant cost compared with the home run architecture.     

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.     

Evolving the Optical Transport Network Management to Integrate Multiple Technologies and Services

Abstract

Optical networks are evolving at a fast pace from traditional synchronous digital hierarchy/synchronous optical network (SDH/SONET) and wavelength division multiplexing (WDM) infrastructures, used by client network layers in overlay mode, to a converged multi-service and multi-technology network able to transport traditional time division multiplexing (TDM) traffic and new packet traffic in a flexible way. Alcatel-Lucent is leading the network transformation required by network providers to offer data transport while guaranteeing the same quality and reliability typical of classical transport services. The introduction of new data communication services requires an evolution of the network management platform that needs to integrate new management applications associated with the new technologies and services. The resulting network has to be integrated from service provisioning and management system viewpoints to optimize its use and to reduce the in-field modifications of the transport network. This article describes specificities in the management of multi-service networks, identifying the management architecture able to support the rapid evolution of such environment.