A cost-effective approach to introduce an optical WDM network inthe metropolitan environment

A case study shows that an optical wavelength division multiplexing (WDM) network can be employed in a metropolitan network in a cost effective way. In part, cost savings are realized due to the total number of line terminals required and the fact that the dimensions of the electrical nodes decrease when exploiting optical cross connects (OXCs) to a large extent. Optical WDM rings are also an important building element when designing a metropolitan network. A number of the properties of WDM rings are classified, resulting in eight different ring architectures. Additional requirements arise when considering ring-to-ring connections. The extent of the rings chosen for the case study is validated from the transmission point of view by a simple model. Finally, as an alternative to an all-optical approach, an opto-electrical approach is presented     

Performance evaluation of an intelligent routed WDM mesh network: An analytical approach

This paper presents an analytical model of an optical mesh network capable of handling WDM traffic intelligently. The router is modeled as a processor to read the instructions in the header of the packet to implement the required algorithm adopting standard queuing concepts. Packet stacking, switching, or routing performance deliberately depends on packet size, node architecture and network parameters. The numerical result shows a huge data transmission through the router with a least dependence on the routing time up to a significant data rate and thus provides a significant improvement in call connection probability.     

Virtual fully connected WDM network: A high-performance single-hop architecture for metropolitan area networks

With the widespread use of broadband access technologies and the development of high-speed Internet backbones, the requirement for high-performance metropolitan area networks (MANs) is increasing. Traditional ring- or star-based metro networks are costly to scale up to high speed and cannot recover from multiple failures, while backbone solutions are too expensive to fit into the cost-sensitive metro market. This paper proposes a virtual fully connected (VFC) architecture for metro networks to provide high-performance node-to-node all-optical transportation. The architecture emulates a fully connected network by providing optical channels between node pairs without intermediate buffering, and thus realizes single-hop transportation and avoids expensive packet routers. In addition, a scheduling algorithm is developed for medium access control and dynamic bandwidth allocation, which achieves 100% throughput and provides a fairness guarantee. Simulations show that the VFC network achieves good performance under both uniform and non-uniform loads.     

Performance of a WDM network based on stimulated Brillouinscattering

The use of stimulated Brillouin scattering as a tunable narrowband amplifier to demodulate, amplify, and select channels in a densely packed WDM (wave-division multiplexed) network is discussed. A 128-channel system configuration is tested with channel separation as small as 1.5 GHz and error rates below 10^-10. Direct FSK (frequency-shift-keyed) modulation of AlGaAs lasers and direct detection receivers are used. The experimental margin and noise analysis indicate that a 1000-channel system can be constructed with only these same components     

A connectivity-based approach for the construction of hierarchical WDM network topology

A hierarchical network model can effectively reduce the complexity of routing and wavelength assignment (RWA) in wavelength division multiplexing (WDM) networks compared to a flat model. However, the resource utilization may greatly suffer if the hierarchical architecture is not properly arranged. By considering the degree of each WDM node and the location effect, this paper proposes a systematic approach to construct the hierarchical topology in WDM networks so that resource utilization can be maximized. Simulation results demonstrate that the performance of the proposed scheme is superior to that of another scheme.

Performance and design evaluation of WDM stars

A performance tool for evaluating the design of a wavelength-division-multiplexing (WDM) passive star is provided. The design parameters that determine the system performance are the number of wavelengths in the system, the number of receivers per node, the wavelength allocation per receiver, the transmitter tunability range, and the node buffer size. An exact analysis becomes prohibitively complex for even moderately sized systems. Therefore, an efficient approximate analysis with drastically reduced computational complexity is presented, incorporating all of the above design parameters, in addition to the channel access protocol and the nonhomogeneous traffic patterns of high-bandwidth networks. The approach produces very accurate results and can help in selecting the most cost-effective system design for given performance requirements     

IP over WDM网络中一种新型虚拓扑构造算法

对IP over WDM的虚拓扑设计算法进行了研究，选择网络整体流量的均衡性作为优化目标，提出了一种新型的虚拓扑构造算法。在算法中，选择负载分布方差作为评价流量均衡性的指标，并给出其定义和计算方法。主要针对拥塞概率性能，在光层和IP层将提出的新型虚拓扑构造算法与其他算法进行比较。在光层的算法比较部分，选择负载均衡启发式路由算法（RLBH，routing with load balancing heuristics）与提出的算法进行比较；在IP层的算法比较部分，选择固定路径最小拥塞路由算法（FPLC，fixed-path least-congestion）与提出的算法进行比较，并对比较结果进行了讨论。比较结果显示在拥塞概率性能方面，提出的新型虚拓扑构造算法优于RLBH算法和FPLC算法。     

宽带城域网解决方案探讨

Ｉｎｔｅｒｎｅｔ的飞速发展 ,带宽需求的进一步增加 ,数据、话音和图像等多种业务融合的需要推进了城域网的演变 ,导致了基于ＩＰ特别是吉位以太网 (ＣＴＥ)之上的宽带城域网建设 ,它能降低成本 ,并迅速整合现存局域网资源。目前国内越来越多的人认为宽带ＩＰ网是比ＡＴＭ更先进、更廉价的网络技术 ,将是今后网络技术的发展趋势。下面简述两种主要的城域网建设方案 ,并介绍城域网的结构和技术特点。1　以ＡＴＭ为骨干的城域网ＡＴＭ发展了多年 ,技术体系成熟而健全 ,一般采用ＡＴＭｏｖｅｒＳＯＮＥＴ/ＳＤＨ方式 ,其优势在于网络资源的统…     

一种生存性军事虚拟网络映射新方法

针对生存性的军事虚拟网络映射问题,提出了生存性的军事虚拟网络映射需要遵循的原则。构建了虚拟网络映射模型,并采用蝙蝠算法进行求解。针对故障情况,提出了区分服务的故障恢复策略,对于高优先级虚网请求提前构建保护路径,对于低优先级虚网请求则提出基于链路可靠性的故障迁移算法,为了减少带宽消耗适当考虑了节点迁移策略。最后通过仿真验证了算法在虚拟网络运行成功率、故障修复率和链路利用率方面相比其他算法具有更好的性能。     

Field trial of full-mesh WDM network (AWG-STAR) in metropolitan/local area

We describe a field trial of a wavelength routing full-mesh wavelength-division-multiplexing (WDM) (AWG-STAR) network for citywide local administration in Japan. An AWG router and five WDM nodes were connected to the existing fiber in the downtown area of the city of Chitose, Hokkaido. A 5 /spl times/ 5 full-mesh network was overlaid on the Chitose intranet. A video-on-demand system based on Gigabit Ethernet links, high-definition serial digital interface signals, and synchronous digital hierarchy signals of STM-16 links are transmitted and routed simultaneously on the wavelength paths of the network. These systems are used for administration and education information sharing for city residents. The network is managed and controlled remotely from the NTT R&D Center in Atsugi, Japan, which is 50 km southwest of Tokyo and approximately 1000 km from Chitose. AWG-STAR exhibits promising potential as a large capacity network system for both simple full-mesh systems and highly secure private networks.     

A wideband all-optical WDM network

We describe some of the results of the Advanced Research Projects Agency (ARPA) sponsored Consortium on Wideband All-Optical Networks in developing architectures, technology components, and applications for the realization of scaleable, wideband, and transparent optical wavelength-division multiplexing (WDM) networks. Our architecture addresses all-optical transport over the wide, metropolitan, and local areas. It utilizes wavelength partitioning, routing, and active multiwavelength cross-connect switches to achieve a network that is scaleable in the number of users, data rates, and geographic span. The network supports two services which can be point-to-multipoint or multipoint-to-multipoint simplex or duplex connections. The A service is a transparent physically circuit-switched service and the B-service is a scheduled time-slotted circuit which is transparent within its time slots. We have developed a 20-channel local and metropolitan area WDM testbed deployed in the Boston area, now undergoing characterization and experimental applications     

Performance analysis of the Rainbow WDM optical network prototype

Rainbow is a prototype optical metropolitan area network (MAN) developed at IBM. It employs wavelength-division multiplexing (WDM) on a fiber-optic, passive-star network topology, with each station equipped with a laser, which is fixed tuned to its own unique wavelength, and a Fabry-Perot filter, which is tunable across all wavelengths. This paper presents a model and analysis of the protocol used in the Rainbow prototype using the equilibrium point analysis (EPA) technique. We examine the system's throughput and how it is affected by various system parameters such as message arrival rate, message length, and timeout duration. We show that, for a given arrival rate, there is a timeout duration that will yield the optimal throughput. The analytical results are verified by simulation     

Performance of WDM fiber-radio network using distributed Raman amplifier

We investigate the impairment induced by stimulated Brillouin scattering (SBS) effect and noise characteristics of wavelength-division-multiplexing fiber-radio network assisted by distributed Raman amplifier (DRA) or erbium-doped fiber amplifier. Experimental results indicate that forward-pumping DRA can increase the link optical output power limited by SBS effect in downstream transmission and backward-pumping DRA can improve signal-to-noise ratio in upstream transmission, which is verified by binary phase-shift keying transmission experiments. Moreover, our experimental results show that DRA does not introduce additional impairment from interchannel crosstalk due to cross-phase modulation and degradation in spur-free dynamic range.     

A slotted access control protocol for metropolitan WDM ring networks

In this study we focus on the serious scalability problems that many access protocols for WDM ring networks introduce due to the use of a dedicated wavelength per access node for either transmission or reception. We propose an efficient slotted MAC protocol suitable for WDM ring metropolitan area networks. The proposed network architecture employs a separate wavelength for control information exchange prior to the data packet transmission. Each access node is equipped with a pair of tunable transceivers for data communication and a pair of fixed tuned transceivers for control information exchange. Also, each access node includes a set of fixed delay lines for synchronization reasons; to keep the data packets, while the control information is processed. An efficient access algorithm is applied to avoid both the data wavelengths and the receiver collisions. In our protocol, each access node is capable of transmitting and receiving over any of the data wavelengths, facing the scalability issues. Two different slot reuse schemes are assumed: the source and the destination stripping schemes. For both schemes, performance measures evaluation is provided via an analytic model. The analytical results are validated by a discrete event simulation model that uses Poisson traffic sources. Simulation results show that the proposed protocol manages efficient bandwidth utilization, especially under high load. Also, comparative simulation results prove that our protocol achieves significant performance improvement as compared with other WDMA protocols which restrict transmission over a dedicated data wavelength. Finally, performance measures evaluation is explored for diverse numbers of buffer size, access nodes and data wavelengths.     

A summary of the HORNET project: a next-generation metropolitan area network

Metropolitan area networks are currently undergoing an evolution aimed at more efficiently transport of data-oriented traffic. However, the incoming generation of metro networks is based on conventional technology, which prevents them scaling cost-effectively to ultrahigh capacities. We have developed a new architecture and set of protocols for the next generation of metro networks. The architecture, named HORNET (hybrid optoelectronic ring network), is a packet-over-wavelength-division multiplexing ring network that utilizes fast-tunable packet transmitters and wavelength routing to enable it to scale cost-effectively to ultrahigh capacities. A control-channel-based media access control (MAC) protocol enables the network nodes to share the bandwidth of the network while preventing collisions. The MAC protocol is designed to transport variable-sized packets and to provide fairness control to all network end users. The efficiency and the fairness of the MAC protocol is demonstrated with custom-designed simulations. The implementation of the MAC protocol and the survivability of the network have been demonstrated in a laboratory experimental testbed. The article summarizes the accomplishments of the HORNET project, including the design, analysis, and demonstration of a metro architecture and a set of protocols. The HORNET architecture is an excellent candidate for next-generation high-capacity metro networks.     

Performance measurements on an ATM-based metropolitan area network: OASICE case study

The city of Colmar is developing a Metropolitan Area Network (MAN) called OASICE. Our MAN uses ATM technology to provide a range of business, academic and community tele-services such as tele-teaching, tele-information, tele-documentation, tele-management and tele-surveillance of property, high definition tele-conference, VOD (Video On Demand), etc. This revised version was published online in August 2006 with corrections to the Cover Date.     

Implementation of STARNET: a WDM computer communications network

STARNET is a broadband backbone optical wavelength-division multiplexing (WDM) local area network (LAN). Based on a physical passive star topology, STARNET offers all users two logical subnetworks: a high-speed reconfigurable packet-switched data subnetwork and a moderate-speed fix-tuned packet-switched control subnetwork. Thus, STARNET supports traffic with a wide range of speed and continuity characteristics. We report the analysis and implementation of an entire STARNET two-node network, from the optical to the computer layer, at the Optical Communications Research Laboratory (OCRL) of Stanford University. To implement the two logical subnetworks, we designed and implemented two different techniques: combined modulation and multichannel subcarrier multiplexing (MSCM). OCRL has already demonstrated several combined modulation techniques such as phase shift-keyed and amplitude shift-keyed (PSK/ASK), and differential phase shift-keyed and amplitude shift-keyed (DPSK/ASK), yielding combined ASK/DPSK modulation receiver sensitivities better than -32 dBm. OCRL has designed and implemented a high-speed high-performance packet-switched STARNET computer interface which enables high-throughput transfer to/from host computer, low latency switching, traffic prioritization, and capability of multicasting and broadcasting. With this interface board, OCRL has achieved average transmit and receive throughputs of 685 Mb/s and 571 Mb/s, respectively, out of the 800 Mb/s theoretical maximum of the host computer bus. The incurred packet latency due to the interface for a specified multihop network configuration has been simulated to be 24 μs. Using simulation and experimental results, it is shown that STARNET is highly suitable for high-speed multimedia network applications     

Performance analysis of multi-fiber WDM network with limited-range wavelength conversion

Wavelength routed optical networks have emerged as a technology that can effectively utilize the enormous bandwidth of the optical fiber. Wavelength conversion technology and wavelength converters play an important role in enhancing fiber utilization and in reducing the overall call blocking probability of the network. In this paper, we develop a new analytical model to calculate the average blocking probability in multi-fiber link networks using limited-range wavelength conversion. Based on the results obtained, we conclude that the proposed analytical model is simple and yet can effectively analyze the impact of wavelength conversion ranges and number of fibers on network performance. Also a new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored. Finally, we analyze network performance with the proposed scheme. It can be observed from numerical simulations that limited-range converters placed at a few nodes can provide almost the same blocking probability as full range wavelength converters placed at all the nodes. We also show that being equipped with a multi-fiber per-link has the same effect as being equipped with the capability of limited-range wavelength conversion. So a multi-fiber per-link network using limited-range wavelength conversion has similar blocking performance as a full wavelength convertible network. Since a multi-fiber network using limited-range wavelength conversion could use fewer converters than a single-fiber network using limited range wavelength conversion and because wavelength converters are today more expensive than fiber equipment, a multi-fiber network in condition with limited-range wavelength conversion is less costly than a single-fiber network using only limited-range wavelength conversion. Thus, multi-fiber per-link network using limited-range wavelength conversion is currently a more practical method for all optical WDM networks. Simulation studies carried out on a 14-node NSFNET, a 10-node CERNET (China Education and Research Network), and a 9-node regular mesh network validate the analysis.     

WDM光包交换城域网关键技术与MAC层协议

介绍了Packet over WDM技术在城域网（MAN）中的两种实现方案，对相应的MAC层协议进行了分析比较，在此基础上对其中应用的关键技术进行了具体说明。最后探讨了未来城域网的发展方向。