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 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.

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.

Performance Monitoring in Transparent Reconfigurable WDM Networks

This paper classifies and surveys different approaches proposed for performance monitoring, in particular the optical signal-to-noise ratio (OSNR) monitoring, in transparent reconfigurable WDM networks. Some considerations for future monitoring schemes are discussed.

Reconfiguring the Logical Topology With Performance Guarantees in WDM Networks

To improve the network performance after traffic demand changes, reconfiguring the logical topology is necessary. We present an ILP algorithm to find out the least lightpath changes needed with guaranteed network performance.

Optical Fiber Devices in WDM Networks

Crystal optics and fiber grating technology are two of the most important optical fiber device technologies. In this paper, we report several new devices developed in Accelink for WDM networks application.

Network coding based all-optical multicast in WDM networks

Wavelength division multiplexing （WDM） has been becoming a promising solution to meet the rapidly growing demands on bandwidth. Multicast in WDM networks by employing free wavelength is an efficient approach to saving bandwidth and cost. However, the free wavelength may not identical between different hops in a multicast light-path, particularly in heavy load optical WDM networks. In order to implement multicast applications efficiently, a network coding （NC） technique was introduced into all-optical WDM multicast networks to solve wavelength collision problem between the multicast request and the unicast request. Compared with the wavelength conversion based optical multicast, the network coding based optical multicast can achieve better multicast performance with paying lower cost.

Integrated Differentiated Survivability in IP over WDM Networks

The problem of differentiated Multi-Layer Integrated Survivability (MLIS) in IP over WDM networks is studied, which is decomposed into three sub-problems: survivable strategies design (SSD), spare capacity dimensioning (SCID), and dynamic survivable routing (DSR). A related work of network survivability in IP over WDM networks is firstly provided, and adaptive survivable strategies are also designed. A new Integrated Shared Pool (ISP) approach for SCD is then proposed, which is formulated by using integer-programming theory. Moreover, a novel survivable routing scheme called Differentiated Integrated Survivability Algorithm (DISA) for DSR is developed. Simulation results show that the proposed integrated survivability scheme performs much better than other solutions (e,g., 'highest layer recovery' and 'lowest layer recovery' schemes) in terms of traffic blocking ratio, spare resource requirement, and average traffic recovery ratio in IP over WDM networks.

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.

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.

Shared-p-cycles method for design of survivable WDM networks

In future high-capacity wavelength division multiplexed(WDM)optical networks,the failure of a network component such as a fiber link can lead to severe disruption in the networks’traffic.Hence,it is imperatively important to provide fast and full protection in WDM optical networks.In this paper,we propose a new approach,called shared preconfigured protection cycles(shared-p-cycles),for the design of survivable WDM networks.We develop an integer linear program(ILP)formulation to solve the problem of shared-p-cycles design for WDM networks with and without wavelength conversion.Numerical results show that the shared-p-cycles design is more efficient in the use of spare capacity and requires much less spare capacity than the conventional pcycles design.

ROUTING AND WAVELENGTH ASSIGNMENT ALGORITHMS BASED ON EQUIVALENT NETWORKS

In this paper, a Wavelength Division Multiplexing (WDM) network model based on the equivalent networks is described, and wavelength-dependent equivalent arc, equivalent networks, equivalent multicast tree and some other terms are presented. Based on this model and relevant Routing and Wavelength Assign- ment (RWA) strategy, a unicast RWA algorithm and a multicast RWA algorithm are presented. The wave- length-dependent equivalent arc expresses the schedule of local RWA and the equivalent network expresses the whole topology of WDM optical networks, so the two algorithms are of the flexibility in RWA and the optimi- zation of the whole problem. The theoretic analysis and simulation results show the two algorithms are of the stronger capability and the lower complexity than the other existing algorithms for RWA problem, and the complexity of the two algorithms are only related to the scale of the equivalent networks. Finally, we prove the two algorithms’ feasibility and the one-by-one corresponding relation between the equivalent multicast tree and original multicast tree, and point out the superiorities and drawbacks of the two algorithms respectively.

Dynamic Routing and Wavelength Assignment for Multi-Lightpath Demands

In wavelength division multiplexing (WDM) networks without wavelengthconversion functionality, we convert the dynamic routing and wavelength assignment problem formulti-lightpath demands to the edge-disjoint paths problem, and propose a new algorithm. Thecomputer simulations show that the proposed algorithm has better blocking probability performancethan a sequential algorithm, which first separates a multi-lightpath demand into mutilplesingle-lightpath demands, then uses the fixed-alternate routing-first fit wavelength assignment(AR-FF) algorithm for each single-lightpath demand.

A Heuristic Algorithm for P-Cycles Configuration in WDM Optical Networks

Aiming at minimizing spare capacity for optical WDM networks, we propose a new heuristic algorithm for preconfigured protection cycle (p-cycle) design. Numerical results show that the spare capacity obtained by our new algorithm is very close to the optimal solution.

Advances in Multi-Terabit, Long-Haul WDM Transmission for Terrestrial Networks

This paper reviews the recent advances in multi-terabit long-haul transmission technologies for terrestrial optical networks. The use of high performance new fibres, low-noise Raman amplification, optimised modulation formats, and forward error correction is shown to be effective for capacity and distance expansion.

A novel model on dynamic resource allocation in optical networks

A novel model on dynamic resource allocation in the WDM optical networks is proposed, basing on the integrated considerations of the impacts of transmission impairments and service classification on dynamic resource allocation in the optical layer. In this model, the priorities of optical connection requests are mapped into different thresholds of transmission impairments, and a uniform method which is adopted to evaluate the virtual wavelength path (VWP) candidates is defined. The Advanced Preferred Wavelength Sets Algorithm (A-PWS) and the heuristic Dynamic Min-Cost & Optical Virtual Wavelength Path Algorithm (DMC-OVWP) are presented addressing the routing and wavelength assignment (RWA) problem based on dynamic traffic and multi priorities in wavelength-routed optical networks. For a received optical connection request, DMC-OVWP is employed to calculate a list of the VWP candidates, and an appropriate VWP which matches the request's priority is picked up to establish the lightpath by analyzing the transmission qualities of the VWP candidates.

Analysis of Crosstalk Induced by Optical Cross-Connection in Multiwavelength Networks

In this paper, Optical Cross-Connection (OXC) induced crosstalk has been carefully analyzed for multiwavelength all-optical networks. Formulae are derived for calculating the crosstalk power of homowavelength crosstalk and the total crosstalk at the receiver end. The results show that the optical switches induced crosstalk dominates over other crosstalk components of OXC, and the accumulated homowavelength crosstalk increases almost linearly with the increasing of the OXC number. At the receiver end , the heterowavelength crosstalk induced by the receiver optical filter has the same order as that of homowavelength crosstalk of OXC. The results of different optical components model are also discussed.

Bidirectional WDM Self-Healing Ring Network for Hub/Remote Nodes

We demonstrate a bidirectional WDM self-healing ring network for hub/remote nodes with one fiber. In this network, self-healing can be achieved within 8 ms. The transmission capacity can be doubled in the operating state.

On the Performance of MLR Optical WDM Network Based on ITU-T Conforming Fibers in the Presence of Dominant Physical Layer Impairments

The tremendous and consistent increase in the volume and heterogeneity of traffic has resulted in major innovations in the telecommunication networks.In regard to the optical networks,existing studies have shown that by adopting a mixed line rate(MLR)strategy,the wavelength division multiplexed optical networks can cost-effectively respond to the diverse variety of traffic requirements which have heterogeneous service demands.Unlike existing studies which focus on various MLR network issues by considering deployment of the standard single mode fiber only within the network,in the current work,we investigate the signal quality deterioration due to the combined effects of dominant physical layer impairments for an MLR optical network conforming to the various ITU-T compliant fibers and also considering the optical frequency grid based on ITU-T Recommendation G.692.The main aim of our current study is to identify,for a given fiber,the modulation format configuration which provides the highest performance.We conduct extensive simulations on the considered MLR system using the obtained optimum channel spacing values between the single and mixed line rates.Our results show that the existence of 10 Gbit/s line rate has a detrimental effect on the 40 Gbit/s and/or 100 Gbit/s line rate;however,the 40 Gbit/s and/or 100 Gbit/s line rate’s effect on a 10 Gbit/s line rate is not so detrimental,as well as between the similar line rates.Overall,our results clearly show that choice of the line rate of both,the central channel and its adjacent channels,has a major effect on the MLR network performance.