Modelling of a WDM Network Using Graph Theory and Dijkstra Algorithm for Traffic Redirection

Optical transport networks are now the basic infrastructure of modern communications systems, including the SDH and WDM backbone network of local network operators, in the case of Cameroon. Given the colossal investments required to deploy these networks, particularly related to the cost of equipment (optical fibers, transponders and multiplexers), the optimization of bandwidth and dynamic allocation of resources is essential to control operating costs and ensure continuity of service. Automatic switching technology for optical networks brings intelligence to the control plane to fully facilitate bandwidth utilization, traffic redirection, and automatic configuration of end-to-end services. This paper considers a local network operator’s WDM network without the implementation of the automatic switching technology, develops a network modeling software platform called Graphic Networks and using graph theory integrates a particularity of the automatic switching technology, which is the automatic rerouting of traffic in case of incident in the network. The incidents considered here are those links or route failures and node failures.

A WDM Add-Drop Multiplexer with Pump-Shared EDFA's for Lightwave Networks

A simple WDM Add-Drop Multiplexer (ADM) Consisting of a set of Er-doped fibers (EDF) and a shared pump is proposed. The chief benefit of the module is that the interchannel power spread does not accumulate from stage to stage in a cascaded WDM system. Moreover, the power differences caused by different component losses existing in the WDM networks can be automatically compressed. The cost will not increase a lot since the pump source is shared in the module. The performance of a cascaded system constructed from the modules has been carefully studied by computer simulation.

Study on Wevelength Allocation Algorithm and Its Optimization of WDM All Optical Networks

In this paper, a new wavelength allocation algorithm based on the minimum number of hops(MNH) is applied to derive the relationships of wavelength requirement with different network parameters. A new modification of the algorithm using the Monto Calo Method is proposed. The results show that using this algorithm, the wavelength requirement of the networks can be optimized. This paper also discuss the effect of multi link optimization of the networks. This approach can further reduce the wavelength requirement and improve the efficiency of resource of the networks. The numerical results show that choosing adequate number of additional links is a key issue to optimize the networks. These algorithms and their results can be used to optimize network design for WRONs.

A Distributed Routing and Wavelength Assignment Algorithm for Online Multicast in All-Optical WDM Networks

Routing and wavelength assignment for online real-time multicast connection setup is a difficult task due to the dynamic change of availabilities of wavelengths on links and the consideration of wavelength conversion delay in WDM networks. This paper presents a distributed routing and wavelength assignment scheme for the setup of real-time multicast connections. It integrates routing and wavelength assignment as a single process, which greatly reduces the connection setup time. The proposed routing method is based on the Prim’s MST (Minimum Spanning Tree) algorithm and the K-restricted breadth-first search method, which can produce a sub-minimal cost tree under a given delay bound. The wave-length assignment uses the least-conversion and load balancing strategies. Simulation results show that the proposed algorithm is suitable for online multicast connection establishment in WDM networks.

Equilibrium Analysis for Anycast in WDM Networks

In this paper, the wavelength-routed WDM network was analyzed for the dynamic case where the arrival of anycast requests was modeled by a state-dependent Poisson process. The equilibrium analysis was also given with the UWNC algorithm.

Network Capacity Analysis of Server Version WDM Optical Networks

In this paper,a new architecture of optical networks—the optical network based on server system is considered.From the point of this new architecture,the network can be modeled as a server system with three type servers—the access server,the node server and the link server. The network performances such as cost,energy consume and network capacity can be affected by the capability of these three type servers.New ILP formulations are proposed to analyze the network capacity under two types of node severs,with and without wavelength converter.Computer simulations are conducted to evaluate the effectiveness of these new formulations.The study has shown that the network can achieve the same throughput under the two types of node servers and the network throughput increases when the maximum allowed variation increases.

A Novel Offline PLI-RWA and Hybrid Node Architecture for Zero Blocking and Time Delay Reduction in Translucent Optical WDM Networks

In this paper, we contrive a model that underpins the offline Physical Layer Impairment-Routing and Wavelength Assignment (PLI-RWA) issue in translucent networks. We introduce an innovative PLI-Signal Quality Aware RWA (PLI-SQARWA) algorithm that (a) guarantees zero blocking due to signal degradation and wavelength contention and (b) aims at minimizing the total required number of network components i.e. regenerators and all-optical wavelength converters (AOWCs). Further, in view of reducing the time delay due to optical-electrical-optical (OEO) conversions, we propose a novel electro-optical hybrid translucent node architecture. We show that PLI-SQARWA outperforms a recent heuristic for RWA and regenerator placement (RP) in terms of capital expenditure (CapEx) and time delay;while demonstrating superior blocking performance at all traffic loads. In addition, at high traffic loads, PLI-SQARWA also starts to provision savings on operational expenditure (OpEx). We proceed to the performance comparison of network equipped with the proposed hybrid node and existing translucent and transparent node architectures. The results clearly show that use of the hybrid node incurs less time delay at a similar blocking performance shown by nodes which use OEO conversion for both, regeneration and/or wavelength conversion. The results presented also highlight the significance of equipping the PLI-RWA routing phase with signal quality awareness in order to reduce the network component count and the use of AOWCs to minimize time delay due to OEO conversions.

A Subsection Shared Restoration Method for Long-Haul WDM Networks

A novel restoration scheme, Parted Path Shared Restoration (PPSR), was proposed. The major idea of PPSR is the strategy of ‘parted disposal’. PPSR keeps the advantage of Path Based Shared Restoration (PBSR) in utilization of capacity. In addition, the restoration time of PPSR is much less than that of PBSR. Furthermore, a satisfaction function was proposed to estimate the performance of PPSR. This function takes the utilization of capacity and restoration time into a harmonious and uniform frame. Through theoretical analysis and computer simulation, the performance of PPSR was demonstrated.

A Novel Optical Control Plane for Switching an Electro-Optical Hybrid Node in Translucent WDM Optical Networks

In a translucent network scenario, development of an optical control plane (OCP) that is aware of the location and number of available regenerators and all-optical wavelength converters (AOWCs) is of paramount importance. However, current generalized multiprotocol label switching (GMPLS) protocol suite does not consider the distribution of regenerator and AOWC availability information to all the network nodes. In this paper, we propose a novel optical control plane (OCP) architecture that 1) disseminates information about network components (i.e. regenerators and AOWCs) to all the network nodes, and 2) evaluates candidate routes which use fewest amounts of network components. Performance of the proposed OCP is compared with a recently proposed hybrid OCP approach in terms of blocking performance, number of deployed components and lightpath establishment setup times. The obtained simulation results show that the proposed OCP approach demonstrates low connection blocking and establishes lightpaths by 1) minimizing the overall network cost owing to the deployment of minimum total number of network components, and 2) demonstrating acceptable lightpath establishment setup times at all traffic loads. Further, the proposed OCP methodology is compatible and suitable for controlling the operations of a novel electro-optical hybrid translucent node which is a latency efficient technology capable of delivering a cost effective implementation suitable for large scale deployment.

Load Balancing in WDM Optical Networks with and without Wavelength-Continuity Constraints

In practical optical networks, there is often the same number of wavelengths in a fiber. But if it is not carefully designed, there will be much difference in link load among different fibers, and unnecessary wavelengths will be needed. This paper investigated this load balancing issues to minimize the wavelength requirements. Both Integer Linear Programming (ILP) and heuristic algorithms were presented to solve such a problem in WDM optical networks with or without wavelength continuity constraints.

FAIRNESS OF SHARING PROTECTION FOR MULTICAST IN WDM NETWORKS

In this paper,the sharing schemes of multicast in survivable Wavelength-Division Multi-plexed(WDM) networks are studied and the concept of Shared Risk Link Group(SRLG) is considered.While the network resources are shared by the backup paths,the sharing way is possible to make the backup paths selfish.This selfishness leads the redundant hops of the backup route and a large number of primary lightpaths to share one backup link.The sharing schemes,especially,the self-sharing and cross-sharing,are investigated to avoid the selfishness when computing the backup light-tree.In order to decrease the selfishness of the backup paths,it is important to make the sharing links fair to be used.There is a trade-off between the self-sharing and cross-sharing,which is adjusted through simulation to adapt the sharing degree of each sharing scheme and save the network resources.

Impact of Channel Dynamics, Combined Nonlinearities and ASE Noise on Transmission Performance of all Optical Star WDM Networks

For all optical Wavelength Division Multiplexing (WDM) network based on G.653 fibers, we investigate the quality factor deterioration due to combined nonlinear effects and Amplified spontaneous emission (ASE) noise for system parameters based on ITU-T Recommendation G.692. The investigation: (a) emphasizes on stimulated Raman scattering (SRS) and four wave mixing (FWM) effects which are the dominant nonlinearities known to limit WDM system performance and (b) accounts for beating between nonlinearities and beating between ASE noise and nonlinearities. Using the proposed model, performance of the worst affected channels due to SRS and FWM is compared and the results indicate that the worst affected channel due to SRS performs better and hence must be preferred for reliable and efficient transmission over the worst affected channel due to FWM. Further, the results suggest that to achieve a desired error rate (quality factor);there exists an optimal value of channel spacing for a given number of channels. The proposed theoretical model is also validated through extensive simulations over Rsoft OptSimTM simulator and the two sets of results are found to match, indicating that the proposed model accurately calculates the quality factor of the all optical WDM network.

Light-Path Provis ioning of the WDM Optical Networks

Provisioning of the WDM optical networks has been a challenge problem because it involves both the physical topology and the logical topology. In addition, the stochastic effects of the traffic mix must be properly characterized. This paper proposes a generic light-path provisioning model and suggests a solution procedure based on a recent mathematical achievement. A case study is also reported.

Blocking Probability in All-Optical WDM Network Using IMCA

The analysis of WDM (Wavelength-Division Multiplexing) optical network is essential to have the routed wavelength blocking probability with the conversion of wavelength using techniques. In this paper, an enhanced analytical model is proposed to evaluate the blocking performances in topology network and to improve the performances of reduction of blocking probability. The variation of probability is based on the wavelength and load used in the network. The conversion is carried out with the support of optical backbone of the inherent flexibility of the network using the proposed IMCA in Sparse-Partial Wavelength Conversion (SPWC) architecture. It reduces the number of converters significantly with efficient process and provides placement scheme of wavelength converters in the network. The proposed model utilizes the network with the assignment and routing of wavelength using dynamic process of assignment algorithm. The proposed model provides dynamic and static routing process with the range limit to have a minimum conversion for the same probabilities of blocking. The proposed system analysis and the simulation results show the better performances in faster coverage, minimum number of conversions, blocking probability improvement for high load.

Next Generation Optical Access Network Using CWDM Technology

We are developing a novel technology for the next generation optical access network. The proposed archi-tecture provides FTTX high bandwidth which enables to give out 10Gbit/s per end-user. Increasing the subscribers in the future will cause massive congestion in the data transferred along the optical network. Our solution is using the wavelength division multiplexing PON (CWDM-PON) technology to achieve high bandwidth and enormous data transmission at the network access. Physical layer modifications are used in our model to provide satisfactory solution for the bandwidth needs. Thus high data rates can be achieved throughout the network using low cost technologies. Framework estimations are evaluated to prove the intended model success and reliability. Our argument that: this modification will submit a wide bandwidth suitable for the future Internet.

基于OFDR/WDM的光纤光栅传感网络研究

应用光频域反射复用技术与波分复用技术 ,解决了光纤光栅传感网络的寻址问题 ;使用可调谐滤波器 ,实现了复用信号的解调 ;具体地分析了光频域反射复用技术的基本原理 ,从理论上推算了系统的空间分辨率和测量范围 ,并进行了 3× 3光栅阵列传感网络的实验研究 该方案充分利用了光信号的频率和波长信息 ,在光源功率足够大的前提下 ,显示出新设计的传感网络具有寻址和解调几百个光栅信号的潜在能力 。

WDM环网保护方式的性能评价及设计原则

WDM环网以其灵活性、管理简单及生存性好等特点受到普遍重视。文章首先讨论了在进行WDM环网保护方式的设计中需注意的几个问题,并对目前可能有的几种WDM环保护方式作详细性能分析,并从不同得角度作了比较,从中得出了一些有益的结论。在此基础上,给出了进行WDM环网保护设计中应遵循的一些原则。所得出的结论对今后WDM环网保护方式的研究与设计都有一定的借鉴和帮助。