Dynamic traffic grooming algorithms for reconfigurable SONET over WDM networks

The emergence of wavelength-division multiplexing (WDM) technology provides the capability for increasing the bandwidth of synchronous optical network (SONET) rings by grooming low-speed traffic streams onto different high-speed wavelength channels. Since the cost of SONET add-drop multiplexers (SADM) at each node dominates the total cost of these networks, how to assign the wavelength, groom the traffic, and bypass the traffic through the intermediate nodes has received a lot of attention from researchers recently. Moreover, the traffic pattern of the optical network changes from time to time. How to develop dynamic reconfiguration algorithms for traffic grooming is an important issue. In this paper, two cases (best fit and full fit) for handling reconfigurable SONET over WDM networks are proposed. For each approach, an integer linear programming model and heuristic algorithms (TS-1 and TS-2, based on the tabu search method) are given. The results demonstrate that the TS-1 algorithm can yield better solutions but has a greater running time than the greedy algorithm for the best fit case. For the full fit case, the tabu search heuristic yields competitive results compared with an earlier simulated annealing based method and it is more stable for the dynamic case.     

Parallel-stage-based reconfigurable optical add-drop multiplexer for WDM optical transport networks

This letter proposes a simple and flexible reconfigurable optical add-drop multiplexer (ROADM) based on parallel-stage configuration using Mach-Zehnder-based fiber gratings, 1/spl times/2 optical switches, and Y-model combiners. The proposed ROADM with four-stage parallel configuration is designed and experimentally investigated to show its performance in full wavelength selection and advantages in reducing the discrepancy of the insertion loss between channels and upgrading.     

A management and visualization framework for reconfigurable WDM optical networks

As the phenomenal advance in optical WDM networking technologies continues, optical WDM network equipment has been deployed not only in backbone networks, but also in regional, metropolitan, and access networks. It is widely believed that a major component of the next-generation Internet will be an IP-based optical network employing WDM. WDM wavelength routing and signaling have become an active research field, and dynamic and adaptive wavelength routing and assignment algorithms have been proposed. However, there is less work on reporting network control and management system implementation efforts over testbed WDM networks. This article presents a network management and visualization framework aimed at guiding the development of management applications for reconfigurable WDM optical networks. A layered framework architecture including element and network management and visualization is provided, and an object-based information model representing the WDM network is introduced. Functional components on reconfiguration, software agent, and network visualization services are presented, and important issues related to optical lightpath generation are discussed. A network visualization service also provides WDM control and management APIs to applications and access networks such as an IP network management system. To illustrate the usage of the framework, we share our experience in implementing the MONET network control and management system, and present network visualization views obtained from the MONET WDM network to highlight the framework features.     

WDM网络中可重构P圈模型的研究

为了解决波分复用(WDM)网络中由于流量分布变化而导致网络中预配置P圈保护资源分配不准确的问题,提出了可重构P圈的概念,并建立了一种基于网络性能参数进行重新配置的P圈模型.在OPNET中搭建仿真平台,基于泛欧COST239网络拓扑结构,对提出的模型进行了验证.仿真结果表明,根据网络的变化重新计算优选P圈,可以降低网络的性能抖动,提高网络的保护资源利用率.     

OEIC WDM transceiver modules for local access networks

The authors report measurements of fibre-optic transceiver modules which use a single optoelectronic integrated circuit (OEIC) subsystem. The optical circuit contains a DFB laser, 3 dB coupler, WDM, monitor photodiode and pin photodetector elements, which are monolithically integrated on a semi-insulating substrate indium phosphide chip. This assembly is designed to provide complete subscriber-termination functionality for bidirectional telephony and unidirectional broadband communication links for access networks. The dual-in-line module provides single fibre network interfacing, is physically compact, is stable for domestic and business environments, requires no cooling, and has the potential to be manufacturable at low cost     

Experimental demonstration of layer-1 multicast for WDM networks using reconfigurable OADM

The feasibility of multicast-capable-reconfigurable optical add/drop multiplexer (MC-ROADM) based on broadcast-and-select switch is experimentally demonstrated. The MC-ROADM can support unicast connection as well as multicast connection, and can provide directionless switching and low insertion loss in path-through channel. We implement fully-reconfigurable multi-degree MC-ROADM based on wavelength selective switch, and evaluate multicasting performances by fully loading 40 × 10 Gbit/s wavelength division multiplexed (WDM) signals. For unicast and multicast operation, measured spectrum and bit-error-rate (BER) show good uniformity and no power penalty. After 1040 km transmission with 25 dB span loss, the measured BER is higher than forward-error-correction (FEC) limit for BER of 10⁻¹⁵.     

Genetic algorithm to design logical topologies in reconfigurable WDM networks

A new method to design logical topologies based on genetic algorithms is presented. Not only does the algorithm determine which nodes should be connected by means of lightpaths with the aim of minimizing congestion, but it also solves the routing and wavelength assignment problem. In this way, the algorithm guarantees that the logical topology obtained can be embedded in the optical network subject to the available set of resources. The algorithm is effective in terms of both congestion and fairness. For instance, when compared with other work, the congestion is significantly reduced (from 20% to 75% depending on the matrix of traffic considered), and the fairness, when evaluated in terms of the Jain index, is generally higher than 0.94. Moreover, the algorithm brings advantages when employed in dynamic scenarios where the logical topology is frequently reconfigured, as it is fast and, in contrast to other algorithms previously proposed, the calculation process can be stopped at any time (if required) in order to give the best virtual topology found up to the moment.

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.     

Efficient routing and wavelength assignment for reconfigurable WDM ring networks with wavelength converters

We consider the problem of wavelength assignment in reconfigurable WDM networks with wavelength converters. We show that for N-node P-port bidirectional rings, a minimum number of /spl lceil/PN/4/spl rceil/ wavelengths are required to support all possible connected virtual topologies in a rearrangeably nonblocking fashion, and provide an algorithm that meets this bound using no more than /spl lceil/PN/2/spl rceil/ wavelength converters. This improves over the tight lower bound of /spl lceil/PN/3/spl rceil/ wavelengths required for such rings given in if no wavelength conversion is available. We extend this to the general P-port case where each node i may have a different number of ports P/sub i/, and show that no more than /spl lceil//spl sigma//sub i/P/sub i//4/spl rceil/+1 wavelengths are required. We then provide a second algorithm that uses more wavelengths yet requires significantly fewer converters. We also develop a method that allows the wavelength converters to be arbitrarily located at any node in the ring. This gives significant flexibility in the design of the networks. For example, all /spl lceil/PN/2/spl rceil/ converters can be collocated at a single hub node, or distributed evenly among the N nodes with min{/spl lceil/P/2/spl rceil/+1,P} converters at each node.     

Online connection provisioning in metro optical WDM networks using reconfigurable OADMs

Optical add/drop multiplexers (OADMs) can significantly reduce the cost of metro optical wavelength-division multiplexing (WDM) ring networks by allowing traffic to bypass intermediate nodes without expensive opto-electro-opto (O-E-O) conversion. Some traditional OADMs, called fixed OADMs (FOADMs), can only add/drop traffic on a specific wavelength. Reconfigurable OADMs (ROADMs) are emerging, which can add/drop traffic onto/from different wavelengths at different time. ROADMs provide desirable flexibility, enable fast provisioning of dynamic traffic, and save capital expenditure (CapEx) and operational expenditure (OpEx). In order to be cost effective, some ROADMs employ architectures that tune the ROADM continuously from one wavelength to another, crossing through all the wavelengths in between, which may cause interference to the connections, if any, on those wavelengths being crossed. In order to prevent existing connections from being interrupted, a constraint needs to be imposed that ROADMs cannot cross working wavelengths when tuning. In this paper, the design and the benefits of metro optical WDM network architectures using ROADMs and the impact of this tuning constraint on the performance of the network are investigated. The dynamic traffic provisioning problem is analyzed and divided into two subproblems: 1) a traditional one on resource allocation; and 2) a new subproblem on tuning-head positioning (TP). Several heuristics for each subproblem are developed to combat the tuning constraint. Results from our simulation experiments show that the tuning constraint can significantly affect the network performance in terms of overall connection blocking probability, and good heuristics for network control and management are needed to overcome this tuning constraint.     

Design of reconfigurable access wrappers for embedded core based SoC test

Testing of embedded core based system-on-chip (SoC) ICs is a well known problem, and the upcoming IEEE P1500 Standard on Embedded Core Test (SECT) standard proposes DFT solutions to alleviate it. One of the proposals is to provide every core in the SoC with test access wrappers. Previous approaches to the problem of wrapper design have proposed static core wrappers, which are designed for a fixed test access mechanism (TAM) width. We present the first report of a design of reconfigurable core wrappers which allow for a dynamic change in the width of the TAM executing the core test. Analysis of the corresponding scheduling problem indicates that good approximate schedules can be achieved without significant computational effort. Specifically, we derive a O(N/sub C//sup 2/B) time algorithm which can compute near optimal SoC test schedules, where N/sub C/ is the number of cores and B is the number of top level TAMs. Experimental results on benchmark SoCs are presented which improve upon integer programming based methods, not only in the quality of the schedule, but also significantly reduce the computation time.     

Applying WDM technology to undersea cable networks

WDM technology is now being applied to international undersea fiber optic cable networks in order to provide enhancements such as increased network capacity and greater network flexibility. This article looks at what WDM technology can provide, the progress being made, and the special challenges in its application in undersea networks. We then describe several international undersea networks that, when completed by the end of 1999, will use WDM technology and will serve as a major part of the global undersea fiber optic infrastructure connecting the world     

Optical WDM transceiver module using wavelength-selective couplerand WDM-PD for optical access networks

A new optical wavelet division multiplexing (WDM)-transceiver module has been designed and fabricated for optical access networks. Conventional 1.3/1.55-μm WDM-coupler and Y-branch were replaced by a new wavelength-selective coupler in order to reduce module size. A new WDM-photodiode (PD), which was photosensitive to 1.3 μm light and transparent to 1.55 μm light, and a 1.55-μm PD were arranged in series along the optical axis. An MQW-FP-LD was used as a 1.3-μm transmitter. Fundamental characteristics were measured and discussed. Evaluation results, P_out of 0 dBm, responsivity of 0.36 A/W at 1.31 μm and 0.74 A/W at 1.55 μm, and IMD2 of -76.2 dBc, imply that this WDM-transceiver module design is promising to application for optical access networks     

Packet labeling technique using electronic code-division multiple-access for WDM packet-based access networks

We propose and experimentally demonstrate the feasibility of a packet labeling technique using electronic code-division multiple-access for a wavelength-division-multiplexing (WDM) packet-based access network, whereby each wavelength is assigned a unique electronic code-based label on a radio-frequency subcarrier. Such a technique allows individual wavelength channels to be electronically identified without requiring the use of a WDM demultiplexer. We experimentally demonstrate this technique with two WDM channels each with 1.25-Gb/s payload data and 10-Mb/s header coded onto an electronic code at 160 Mb/s. The experimental results and theoretical analysis show that this technique has the potential to support large numbers of WDM channels.     

RSOA在光接入网TDM/WDM混合PON中的应用

介绍了RSOA的工作原理、技术指标以及它在TDM-/WDM混合PON网络中的应用.实际应用表明,RSOA在50mA下,小信号光增益可达28dB、输出光功率6dBm,噪声指数6.5dB;讨论、分析了RSOA的温度稳定性、噪声指数和激射等问题.     

光接入网中的ECDM-PON技术(本期优秀论文)

基于电码分多址的无源光网络是一种新型的光接入网技术.文章首先介绍了ECDM-PON的基本结构,然后分析了ECDM-PON的关键技术,特别是以CCD-MF为基础的新型的相关和判决技术,以及超长距离传输的特点.最后,展望了ECDM-PON的应用前景.     

Experimental demonstration of a multiple-/spl lambda/ wavelength shifter for dynamically reconfigurable WDM networks

We demonstrate a multiple-/spl lambda/ wavelength shifter that is based on temporal interleaving and semiconductor optical amplifier cross-gain compression. Our multiple-/spl lambda/ wavelength shifter is transparent to both the nonreturn-to-zero (NRZ) and return-to-zero (RZ) input data-formats. We simultaneously wavelength shift two independent NRZ 1-Gb/s WDM channels from 1548 and 1552 nm to 1540 and 1569 nm, respectively, with low-power penalties.     

TINA for services and advanced signaling and control in nextgeneration networks

This article describes solutions that use the Telecommunications Information Networking Architecture and its advanced service architecture and call model, for the definition of services and advanced signaling and control in next-generation networks. It presents both the solutions for extending traditional signaling and/or interacting and interworking with it, and the way the TINA service architecture can constitute an intelligent service platform providing multiple value-added services to the PSTN and the Internet. In each case, the article provides details and examples to demonstrate the case and illustrate the solutions for trendy technologies such as mobile and the Internet     

A slotted MAC protocol for efficient bandwidth utilization in WDM metropolitan access ring networks

The paper proposes an original wavelength-division multiplexing slotted-ring network architecture with nodes that use one fixed transmitter and fixed receivers. It is shown, through theoretical predictions and simulation results, how a simple slotted medium access control protocol can be implemented to achieve fairness between access nodes and efficient bandwidth utilization when used in a metropolitan access network. Performance for both source and destination stripping schemes has been analytically derived and simulated with a realistic self-similar traffic model. A modified node architecture using a tunable receiver has also been considered and the impact of receiver collisions has been evaluated and analyzed. Finally, the effect of using unbalanced traffic sources has also been analyzed and simulated.