Double-link failure protection algorithm for shared sub-path in survivable WDM mesh networks

We propose a novel shared sub-path protection (SSPP) algorithm to protect the double-link failures in wavelength division multiplexing (WDM) mesh networks. SSPP segments the primary path into several equal-length sub-paths and searches two link-disjoint backup paths for each sub-path. When computing the paths, SSPP considers the load balance and the resource sharing degree, so that the blocking ratio can be effectively reduced. The simulation results show that SSPP not only can completely protect the double-link failures but also can make the tradeoffs between the resource utilization ratio (or blocking ratio) and the protection-switching time.     

A new green multicast grooming protection algorithm in WDM optical networks

Since optical network carries a lot of traffic, survivability is very important to ensure the service continuity against network failures. Recently, multicast services become more popular to meet the huge multimedia demand in network, so that multicast survivability in optical network has got more attention. However, multicast survivability may lead to more energy consumption due to more redundant backup resources allocated. Since greening network is particularly important with the energy crisis keeping growing, green multicast survivability in optical network is a challenging issue. This paper focuses on the green multicast grooming protection problem in optical network and designs two auxiliary graphs that includes a virtual topology graph and an integrated graph to address the survivable multicast grooming, routing and wavelength assignment. Based on the auxiliary graphs, this paper proposes an efficient heuristic called green multicast grooming algorithm based on spanning path dedicated protection (GMG-SPDP), in which the network reliability and the energy efficiency are jointly taken into account. Simulation results show that, compared to other algorithms, the proposed GMG-SPDP not only has lower blocking probability and higher bandwidth utilization ratio, but also saves more energy.     

Dynamic waveband grooming based on hierarchical integrated grooming auxiliary graph in multi-domain mesh optical networks

With the number of wavelengths in fibers increasing, the number of optical switching ports in conventional Optical Cross-Connect (OXC) keeps enhancing, so that waveband grooming technique is proposed to save the switching ports in OXC. Most of previous works focused on waveband grooming in single-domain optical network. Since the current optical backbone is actually divided to multiple domains according to the different network providers, it is necessary to study the waveband grooming in multi-domain optical networks. However, waveband grooming in multi-domain optical networks is more challenging than that in single domain networks because of the routing scalability and security issues. Therefore, in this paper, we propose a new heuristic Hierarchical Multi-domain Waveband Grooming (HMWG) algorithm based on Hierarchical Integrated Grooming Auxiliary Graph (H-IGAG) to reduce the total number of optical switching ports. The H-IGAG is compared of the Intra-domain Waveband Integrated Auxiliary Graph (Intra-WIAG) and the Inter-domain waveband Virtual Topology Graph (Inter-VTG). For the demand in single-domain, HMWG directly computes the route from the source node to destination node in the single-domain with waveband grooming on Intra-WIAG. For the demand spanning different domains, HMWG first computes the route from the source node to the selected border node in source domain and computes the route from the selected border node to the destination node in destination domain with waveband grooming on Intra-WIAG, respectively. Then, HMWG computes the route from the selected border node in source domain to the selected border node in destination domain with waveband grooming on Inter-VTG. Simulation results show that, compared with previous grooming algorithm, HMWG can obtain better performance.     

Multicast protection algorithms based on aggregated logical topology in survivable multi-domain optical networks

Since the optical network carries a lot of traffic, the survivability is an important issue to ensure the service continuity. At the same time, with the network scale increasing, the optical network has been divided into multi-domains each of which is managed by a unique network provider. Therefore, the survivability in multi-domain optical networks has got more attention in recent years. However, current works mostly addressed the unicast survivability and few or no solved the multicast survivability in multi-domain optical networks. Therefore, in this paper we propose two heuristic algorithms called Multicast Multi-domain Dedicated Protection (MMDP) and Multicast Multi-domain Shared Protection (MMSP) to provide the survivability in multicast multi-domain optical networks. In MMDP and MMSP, to provide the intra-domain protection, we use the modified Minimal-cost Path Heuristic (MPH) algorithm to compute the intra-domain survivable multicast tree. To provide the inter-domain protection, based on multi-domain logical topology, we firstly use the MPH algorithm to compute the inter-domain logical multicast tree and then use the Dijkstra algorithm to compute the inter-domain logical backup sub-path for each inter-link on this logical multicast tree. Simulation results show that MMSP has better resource utilization efficiency and lower blocking probability.     

An optimal protection and restoration scheme (OPARS) for optical networks

Protection and restoration are critical network design issues for optical networks since even a single failure for a short duration may result in huge data loss due to the large capacity of optical fibers. However, few studies have been done on these issues for optical burst switching (OBS) networks. Protection and restoration are essential mechanisms for guaranteeing more reliable traffic delivery services. But it is not easy to apply existing mechanisms to optical burst switching (OBS) networks due to its one-way reservation signaling and the statistical burst multiplexing. Thus, to achieve the high transmission performance and reliability simultaneously, unique properties of OBS must be considered in the design of protection scheme. In this paper, an optimal protection and restoration scheme (OPARS) has been introduced that not only optimizes the number of provisioned protection wavelengths adaptively based on the traffic load as well as the quality of service (QoS) requirements of bursts in high speed networks but also minimizes burst loss rates. In addition, the proposed scheme has been used as an efficient contention resolution technique. The simulation results verify that the proposed scheme improve the network resource and channel utilization while guaranteeing the targeted protection reliability and QoS requirements of bursts.     

A new protection algorithm with consideration of lightpath load in fault-tolerant GMPLS optical networks

In this paper, we study the survivability in GMPLS optical networks and propose a new algorithm called Protection based on Lightpath Load (PLL) to tolerate the single-fiber link failure. Based on the parameter, Boundary of Heavy-load Lightpath (BHL), PLL can effectively choose the protection execution whether on optical layer or on IP/MPLS layer, such that the bandwidth utilization and recovery complexity can be compromised. In PLL, if the number of Working Label Switching Path (WLSPs) carried on a Working Lightpath (WLP) exceeds the value of BHL, this WLP will be protected in optical layer; otherwise, these WLSPs carried on this WLP will be protected on IP/MPLS layer. Simulation results show that, compared to conventional protection algorithm, PLL not only can significantly reduce the recovery complexity but also can obtain satisfactory trade-off performance.     

Survivable routing and spectrum allocation algorithm based on p-cycle protection in elastic optical networks

With the number of large capacity applications in core network increasing, the bandwidth requirement of optical connections in conventional Wavelength Division Multiplexing (WDM) networks keeps enhancing, so that the Orthogonal Frequency Division Multiplexing (OFDM) technology is adopted to provide higher spectrum efficiency and flexibility in the future elastic optical networks. Meanwhile, survivability in the conventional WDM optical networks has been widely studied as an important issue to ensure the service continuity. However, survivability in OFDM-based elastic optical networks is more challenging than that in conventional WDM optical networks because each fiber usually carries even more connections. Therefore, it is necessary to study the new lightpath protection algorithm in elastic optical networks. Since p-cycle protection scheme has short restoration time and simple protection switching procedure, in this paper, we study the static Survivable p-Cycle Routing and Spectrum Allocation (SC-RSA) problem with providing an Integer Linear Programming (ILP) formulation. Since RSA is a NP-hard problem, we propose a new heuristic algorithm called Elastic p-Cycle Protection (ECP) to tolerate the single-fiber link failure. For each demand, ECP scheme can compute highly-efficient p-cycles to provide protection for all of the on-cycle links and the straddling links. We also consider the load balancing and choose the proper working path for each demand. Simulation results show that the proposed ECP scheme achieves better performances than traditional single-line-rate survivable schemes.     

K-dimensional protection structure (KDPS) for multi-link failure in data center optical networks

Currently, data center has become one of the most important application resources. Meanwhile, there is huge amount of data streams within a data center or among different data centers, which requires the transmission channel with high bandwidth and good reliability. Optical networks become the essential solution for the data center interconnection. Especially for intra data center networks, there are too many links for a limited number of nodes, which make the network so complex and vulnerable. A K-dimensional protection structure (KDPS) is proposed against multi-link failure in data center optical networks, and 3DPS is mainly introduced and analyzed in the paper. Two greedy algorithms are proposed to construct KDPS in static and dynamic optical networks respectively. Numerical results show that 3DPS can be constructed with more difficulty in dynamic optical networks, and the greedy algorithm can find the 3DPS much easier under three-link failures than under dual-link failures.     

Dynamic protected lightpath provisioning in mesh WDM networks

This paper investigates the problem of dynamic protected lightpath services provisioning in optical mesh networks employing wavelength division multiplexing (WDM). A variety of schemes for dynamic protected services provisioning have been proposed, supporting a range of tradeoffs among restoration speed, capacity efficiency, and scalability. In this paper, we propose a novel scheme, called p-cycles-based maximum protected working capacity envelope (PC-MPWCE), which can offer an attractive combination of fea-tures: ring-like speed, mesh-like capacity efficiency, and good scalability. To evaluate the performance of PC-MPWCE, we compare it via simulation with 1 + 1 automatic protection switching (APS) and two well-known shared backup path protection (SBPP) on NSFNET. Our simulation results show that PCMPWCE can achieve much better blocking performance than 1 + 1 APS, and perform the similar blocking performance and capacity efficiency as SBPP.     

Optimization of optical communication window mesh through full-wave analysis of periodic mesh

In order to develop an optical communication window mesh with good optical transmittance and shielding effectiveness at the same time, models were established for the shielding effectiveness and optical transmittance of optical communication window mesh, verified through experiments, and used to run full-wave analyses. The effect of period and linewidth of mesh on the shielding effectiveness and optical transmittance of optical communication window mesh was investigated through simulation. Simulation results indicated that better optical transmittance can be achieved using optical communication window mesh with high porosity and finer linewidth while the given shielding effectiveness requirement is satisfied.     

Restoration approach in WDM optical networks

Critical applications require proactive-based survivability strategy which provides 100% degree of survivability, low blocking probability and very low restoration time. In this paper, we have proposed an efficient proactive restoration approach for WDM optical network that efficiently utilizes the resources and reduces blocking probability as compared to existing proactive restoration approach. It gives priority to primary lightpath as compared to backup lightpath because primary lightpath should not share resources with other lightpaths in critical applications but backup lightpaths can share the resources, i.e. backup multiplexing.     

Wavelength conversion in optical transport networks

The introduction of optical technology in the path layer of a transport network is analyzed; in particular, the impact of all-optical wavelength conversion is examined. Two basic optical cross-connect schemes based on space switching and on wave-length switching, respectively, and two types of wavelength converters are considered. The wavelength converters are, respectively, based on four-wave miring (FWM) in semiconductor optical amplifiers (SOAs) and on cross-phase modulation (XPM) obtained by two SOAs put in an interferometric configuration. An analysis of transmission performances of optical transport networks employing both types of wavelength conversion and both the node architectures is reported. The performances are evaluated by means of a system modeling that facilitates considering physical phenomena occurring during transmission and all the important transmission impairments. The analysis reveals that both the types of converters can be employed with different features and limitations, according to the considered network and switching architecture.     

SDH/SONET网络中的虚级联保护

分析了虚级联的传输延时和由LCAS协议引入的固定延时。在现有的SDH/SONET网络中,仅采用复用段保护或通道保护不能完全满足生存性的要求。基于它们各自的优点提出了组合保护的方法。通过仿真和分析,组合保护在恢复率和恢复时间上优于复用段保护和通道保护。     

Tunable holographic components in WDM optical networks

This paper describes the applications of a multipurpose holographic device in optical networks with Coarse and Dense Wavelength Division Multiplexing (CWDM/ DWDM) technologies. In its basic structure, it can operate as a tunable wavelength filter, wavelength multiplexer or λ router. By using a more complex structure, the device works as OADM (Optical Add Drop Multiplexer) or OS (Optical Switch). Some simulations of the basic devices, from the optical transmission point of view, are made to match the transmission parameters for the application in optical networks. Performance parameters of the device, like switching time, losses, cross-talk or polarization insensitivity are analyzed and compared with other multiplexing or switching technologies. To complete the review of these components, a study of computer generated holograms (CGH) design is carried out. The results are used in the design of holographic devices to perform different applications: in Metro networks, where a design of a holographic device with wavelength conversion and routing is analyzed, or, in Access Networks like a tunable filter or demultiplexer in Fiber to the Home/Business (FTTH/FTTB) topologies.     

All‐optical virtual private network in passive optical networks

We review recent progress on all‐optical virtual‐private‐network (VPN) schemes in passive optical networks (PONs). PON is a promising candidate in future access areas to provide broadband services with low cost. With all‐optical virtual private network (VPN) function, PON can support efficient internetworking among end users with dedicated optical channels, thus enabling guaranteed bandwidth and enhanced security at the physical layer. Here, we discuss and compare existing schemes of all‐optical VPNs in time‐division‐multiplexed (TDM) PONs, and also recently proposed schemes for deployment in wavelength‐division‐multiplexed (WDM) PONs and two‐stage TDM/WDM PONs.     

Impairment-aware traffic grooming in WDM optical networks

<正>A novel heuristic algorithm that considers transmission impairment(especially amplified spontaneous emission(ASE) noise) is developed for traffic grooming in wavelength division multiplexing(WDM) optical networks.Span constraints,which are determined by the impairment,are added to constrain the maximal transparent reach limit of a lightpath.Under span constraints,a series of short lightpaths will be built up explicitly to relay traffic when a single lightpath cannot meet the requirement of transmission quality.Both problem formulations and heuristic algorithms are given for impairment-aware traffic grooming.Numerical results show that the successful routing of each low-speed traffic stream is guaranteed and the efficiency of wavelength channels and lightpath usage are both improved by considering transmission impairment.     

Localisation of optical modes in complex networks

Polarimeters were developed to measure the polarization of the proton beam at RHIC in relative scale through the asymmetry measurement of the elastic proton-carbon scattering. Recoil carbon ions with kinetic energy of 400 ≤ E ≤ 900 keV were detected by silicon strip detectors installed at 90° with respect to the beam. The absolute polarization is given by normalizing against another polarimeter implemented at RHIC, namely a polarized hydrogen gas jet polarimeter. In this report, the details of polarization measurements, data analysis, and systematic uncertainties are discussed based on the data taken during √s = 200 GeV operation of Run05 at RHIC.     

Advanced multifunctional optical switch for multimode optical fiber networks

In this work, an advanced multifunctional optical switch based on multimode fibers is proposed. It can work as a 3 × 1 optical multiplexer/combiner, a 2 × 2 optical switch, a variable optical attenuator and a variable optical power splitter. All these functionalities can be developed in the same device without any hardware modification, only by using the proper ports and control electronics.The proposed switch has been developed for being used in the visible and near infrared wavelength range: 450–650 nm for optical fiber automobile applications, 650–850 nm for home broadband applications; and 850–1300 nm for multimode fiber access networks. Up to three different types of twisted nematic liquid crystal cells have been designed and fabricated for fulfilling these different wavelength ranges as part of the proposed device.The multifunctional switch has been implemented and experimentally tested. Crosstalk usually better than ? 15 dB at 532 nm, 660 nm and 850 nm, in any state has been measured. Switching is achieved at voltage levels of 4 Vrms. Fiber to fiber insertion losses when operating as a 2 × 2 optical switch, range from 10 to 15 dB within 200 nm wavelength range; with a non-optimized optics for collimation and coupling.     

Splitting algorithm for DMT optimal cooperative MAC protocols in wireless mesh networks

A cooperative protocol for wireless mesh networks is proposed in this paper. The protocol implements both on-demand relaying and a selection of the best relay terminal so only one terminal is relaying the source message when cooperation is needed. Two additional features are also proposed. The best relay is selected with a splitting algorithm. This approach allows fast relay selection within less than three time-slots, on average. Moreover, a pre-selection of relay candidates is performed prior to the splitting algorithm. Only terminals that are able to improve the direct path are pre-selected. So efficient cooperation is now guaranteed. We prove that this approach is optimal in terms of diversity-multiplexing trade-off. The protocol has been designed in the context of Nakagami-m fading channels. Simulation results show that the performance of the splitting algorithm does not depend on channel statistics.