Wavelength-routed Optical Networks Research Articles

Topological Structure and Physical Layout Co-Design for Wavelength-Routed Optical Networks-on-Chip

The wavelength-routed optical network on chip (WRONoC) is a promising solution for signal transmission in modern System-on-Chip (SoC) designs. Previous works do not simultaneously handle all the following four main issues for WRONoCs: 1) correlations between the topological structure and physical layout; 2) tradeoffs between the maximum insertion loss and the number of wavelengths; 3) runtime scalability of wavelength assignment scheme; and 4) a fully automated flow to generate predictable designs. As a result, their insertion loss estimation is inaccurate, their wavelength assignment is inefficient, and thus, only suboptimal results are obtained. To remedy these disadvantages, we present a fully automated topological structure and a physical layout co-design flow with improved wavelength assignment schemes to minimize the maximum insertion loss and the laser power simultaneously with a significant speedup. The experimental results show that our co-design flow significantly outperforms state-of-the-art works in the maximum insertion loss, laser power, and runtimes.

Wavelength-routed optical backbone network planning under fuzzy environment

Wavelength-routed optical backbone network planning under fuzzy environment

Energy-efficient all optical wavelength converter for optical phase conjugation

Abstract All-optical wavelength converters (AOWCs) based on state-of-the-art highly nonlinear optical fibers (HNLFs) are best matched with future large-capacity optical networks because of their characteristic of fast response. AOWCs play important roles in wavelength-routed optical networks to alleviate the constraint of conflicted wavelengths and in optical phase conjugation networks to mitigate the effects of fiber nonlinearities. Generally, conversion efficiency (CE) is a key evaluation index of AOWCs and higher CE corresponds to better transmission performance. However, it is challenging to achieve higher CE because the launched pump powers into HNLFs are usually limited by their stimulated Brillouin scattering thresholds. Actually, the performance of AOWCs, i.e., that of the idlers, depends on both of their CEs and the signal powers. Thus, it is feasible to achieve good performance for AOWCs with lower CEs as that with higher CEs by optimizing the launched signal powers into HNLFs. Our experimental results verified the above proposal in the AOWCs with the CEs of –23.1 dB, −19.1 dB, −15.2 dB, −11.4 dB and −7.9 dB. The proposed AOWCs was used as optical phase conjugation in the 64-QAM coherent optical transmission experimental system and good compensation performances have been achieved under the above five operating conditions.

Physical layer impairment-aware shared path protection in wavelength-routed optical networks

In this paper, physical layer impairment (PLI)-aware shared path protection (SPP) scheme for single-link failures in transparent optical WDM mesh networks is considered. We propose PLI-aware integer linear programming (ILP) and heuristic algorithm for both SPP and dedicated-path protection (DPP) schemes. The objectives are to maximize the network resource utilization and minimize the quality of transmission (QoT) blocking probability, restoration time, and computational time. Both the ILP and the heuristic algorithm are evaluated, and their performance is compared. The heuristic algorithm is evaluated with extensive simulations over different network topologies. The solution obtained from the PLI-unaware SPP and DPP serves as the base line to evaluate the performance of our heuristic algorithm. The simulation result shows that the proposed algorithm is efficient and improves the QoT-blocking probability significantly. It achieves $$100\%$$ restorability and improves the network utilization up to $$73\%$$ . The result also shows an improvement in computational time.

Wavelength Assignment Vs. Wavelength Converter Placement in Wavelength-Routed Optical WDM Networks

In this paper, we deal with the wavelength assignment and the converter placement problem in wavelength-routed optical WDM Mesh networks. Our objective is to try to assign wavelengths in an efficient manner with/without wavelength conversion to get a very low blocking probability and optimize the performance of the overall network. Thus, we implement and compare the performance of two proposed algorithms namely DWA “Dynamic Wavelength Assignment” and SWA “Static Wavelength Assignment” with well-known algorithms. We first present a literature review about previously proposed approaches, and then we introduce and evaluate our implemented approaches. We also discuss the wavelength converter placement problem in mesh networks. We finally corroborate our theoretical findings through extensive simulations.

An improved algorithm for RWA problem on sparse multifiber wavelength routed optical networks

Hitherto, several algorithms have been proposed for routing and wavelength assignment (RWA) problem on single or multifiber wavelength routed optical network (WRON) with or without wavelength converters. However, due to budget limit, we may equip only a few links in the network with multi fibers, and hence we have a sparse multifiber WRON (SM-WRON). Here, we consider the RWA problem on an SM-WRON without wavelength conversion. Different number of links are considered to equip with multi fibers to make an SM-WRON. Two basic techniques to select the required links to make them multifiber are random-choice and first-choice. The earlier one selects some links randomly and the later one selects the first numbered links. Here, in order to propose an improved algorithm, we define a cost for every link in the network, and then equip the most expensive links with multi fibers. The numerical results made on the well known benchmark networks, i.e., ARPANET and NSF topologies, show the proposed technique to be more efficient than the basic ones taking the blocking probability into account.

Cyclic spectra for wavelength-routed optical networks.

We propose occupying the guard bands in closely spaced WDM systems with redundant signal spectral components to increase tolerance to frequency misalignment and channel shaping from multiplexing elements. By cyclically repeating the spectrum of a modulated signal, we show improved tolerance to impairments due to add/drop multiplexing with a commercial wavelength selective switch in systems using 5%-20% guard bands on a 50 GHz DWDM grid.

Energy-Efficient Routing and Spectrum Assignment Algorithm with Physical-Layer Impairments Constraint in Flexible Optical Networks

AbstractThe recently proposed flexible optical network can provide more efficient accommodation of multiple data rates than the current wavelength-routed optical networks. Meanwhile, the energy efficiency has also been a hot topic because of the serious energy consumption problem. In this paper, the energy efficiency problem of flexible optical networks with physical-layer impairments constraint is studied. We propose a combined impairment-aware and energy-efficient routing and spectrum assignment (RSA) algorithm based on the link availability, in which the impact of power consumption minimization on signal quality is considered. By applying the proposed algorithm, the connection requests are established on a subset of network topology, reducing the number of transitions from sleep to active state. The simulation results demonstrate that our proposed algorithm can improve the energy efficiency and spectrum resources utilization with the acceptable blocking probability and average delay.

Comprehensive design methodology for control and data planes in wavelength-routed optical networks

We propose a comprehensive design methodology for control and data planes of wavelength-routed optical networks (WRONs) employing mixed-line-rate (MLR) transmission for cost-effective resource provisioning. The proposed approach attempts to minimize the maximum lightpath capacity demand in Gbps (representing the measure of lightpath congestion) in network for a given traffic matrix by using a mix of a heuristic scheme and linear programming (LP). In the first step of the proposed three-step design, some lightpaths are set up on a set of judiciously selected fiber links (with point-to-point lightpaths between neighboring nodes), on a specific wavelength throughout the network, and an appropriate fraction of the same set of lightpaths is utilized for carrying control information, forming therefore the control plane (CP) of the WRON. The remaining bandwidth of these lightpaths is utilized to carry the data traffic along with all other designed lightpaths of the WRON using appropriate algorithm, forming the overall data plane (DP) of the WRON. In the second step, traffic routing is carried out through LP to minimize lightpath congestion in the network. In the third step, we utilize the results of LP to assign rates to lightpaths, such that the cost (considering only the transceiver cost) of the network is minimized. This design leads to congestion-aware MLR network with due consideration to cost-effectiveness without compromising the network restoration response against link failures. We carry out simulation studies employing possible CPs using both symmetric (CP topology being same as the physical topology) as well as asymmetric (using fewer fiber links than the symmetric case) topology. The results of our simulations indicate that the proposed design of CP with symmetric/asymmetric topology and in-band transmission with sub-lightpath capacity can bring down network congestion and cost with respect to symmetric out-of-band transmission (using fully reserved lightpaths for CP), without any perceptible sacrifice in respect of the network restoration time. Failure can occur either in CP or DP, or in both the planes. We investigate the effect of design of CP with symmetric/asymmetric topology on network restoration time for single- and double-link failures. We further present DP design methodology with hybrid restoration scheme, i.e., combination of dedicated (1:1) path protection and path restoration. We analyze the effect of symmetric CP topology and degree of protection on the congestion of the network. Some lightpaths, that support more traffic, are protected against failures, while the others are left for path restoration in the event of failures. As more lightpaths are protected, the congestion and power consumption of network increase. We provide an analysis of the factors that come into play while altering the degree of protection and observe how the choice for the degree of protection in DP can be arrived at using an appropriate design methodology.

Distributed meta-scheduling in lambda grids by means of Ant Colony Optimization

Data transport infrastructures based on wavelength-routed optical networks are appealing to the grid community because they can provide a reconfigurable and high-bandwidth network service to emerging data-intensive grid applications. Traditionally, the control plane of those optical networks is independent from the management of other resources, such as computing systems, and it is commonly limited to fulfill immediate reservation demands of lightpaths. However, the lack of network integration to grid resources and the absence of advance reservation of bandwidth are critical aspects to the widespread adoption of optical networks in grid environments. Therefore, in this work, a distributed grid meta-scheduler based on an Ant Colony Optimization (ACO) algorithm is proposed, which is capable of co-allocating both optical networking and grid resources, under an integrated, extended and distributed control plane that supports advance reservations. The blocking probability and the delay for starting the processing of a request are evaluated for the proposed meta-scheduler under different resource co-allocation algorithms and different meta- and local scheduling policies, including the influence of the information aggregation across grid nodes. In addition, the benefits of the proposed approach are shown, such as grid and networking resource integration at the control plane, and capital expenditure reductions at the deployed optical network when compared to an immediate reservation scenario.

Analysis of Ant Colony Optimization-based routing in optical networks in the presence of byzantine failures

Byzantine failures during the execution of the routing algorithm may degrade or disrupt the normal operation of the network. Ant Colony Optimization (ACO)-based routing algorithms are especially vulnerable to those failures. In this work, we propose the use of crankback re-routing extensions associated to the ACO algorithm in wavelength-routed optical networks to deal with byzantine failures. We investigate three different byzantine failure scenarios: misdirection of forward ants, dropping of forward ants and dropping of backward ants. Those failures affect the routing information of the network, but they are very hard to detect and cannot be fully addressed by integrity and authentication techniques. Without any need for a byzantine failure detection mechanism, simulations have demonstrated that the proposed approach is effective in mitigating the impact on the blocking probability due to network nodes exhibiting a byzantine behavior.

A Novel Weighted Energy Efficient Routing and Spectrum Assignment Algorithm in Flexible Optical Networks

AbstractThe network resource utilization efficiency is limited by the rigid nature of the current wavelength-routed optical networks. The recently proposed flexible optical network can allocate the spectral resources adaptively according to the traffic demand. Meanwhile, the transmission quality has always been a main objective during the routing process in optical networks. Recently, the energy efficiency has also been a hot topic because of the energy consumption problem. In this paper, we propose a novel weighted energy efficient routing and spectrum assignment scheme based on the designed quality of transmission (QoT)-energy estimation model in which the physical impairments and energy consumption are given consideration to two or more things. The simulation results demonstrate that the proposed algorithm can make a better balance between the quality of service (QoS) and energy efficiency.

On methodologies to estimate optical-layer power consumption and cost for long-haul WDM networks with optical reach constraint

This paper deals with the methodologies to obtain the estimates of optical-layer power consumption and cost for long-haul optical networks using wavelength-division multiplexing (WDM) with IP-over-WDM and IP-over-MPLS-over-WDM network settings. Such optical networks generally employ wavelength routing at intermediate nodes and are known as wavelength-routed optical networks (WRONs). In WRON-based long-haul networks, optical reach (OR) of a transponder represents the maximum distance over which its optical signal can travel without any optical/electrical/optical regeneration and plays a significant role in deciding the power consumption and cost of the optical layer. In IP-over-WDM network setting, IP routers are directly interfaced with WRON and bandwidth requests are equal to the lightpath capacity. In IP-over-MPLS-over-WDM network setting, IP routers are interfaced with WRON via MPLS routers and bandwidth requests arrive as label-switched paths, which are generally lower than the lightpath capacity. We examine the above networks with mixed-OR nodes (transponders in each WRON node having different OR values but all transmitting at 10 Gbps) and fixed-OR nodes (transponders in each WRON node having same OR value and 10 Gbps transmission rate). In this investigation, two types of control planes are considered, namely unified control plane and isolated control plane. The network with unified control plane supports automated and dynamic resource provisioning for both short-term and long-term bandwidth requests. The study on nonautomated network using isolated control plane considers resource provisioning only for long-term bandwidth requests. Simulation-based network provisioning is carried out using C++, considering appropriate traffic models, OR constraints, node configurations and network architectures. The results of our simulations indicate in general how OR of the transponders can influence the total network cost and power consumption in optical layer. Overall, the nonautomated networks with mixed-OR configuration are found to save power and offer lower cost with respect to fixed-OR configuration, while the automated networks with mixed-OR configuration can save power while the cost increases with respect to fixed-OR option.

Towards a scalable, low-power all-optical architecture for networks-on-chip

This article proposes a scalable wavelength-routed optical Network on Chip (NoC) based on the Spidergon topology, named Power-efficient Scalable Wavelength-routed Network-on-chip (PeSWaN). The key idea of the proposed all-optical architecture is the utilization of per-receiver wavelengths in the data network to prevent network contention and the adoption of per-sender wavelengths in the control network to avoid end-point contention. By performing a series of simulations, we study the efficiency of the proposed architecture, its power and energy consumption, and the data transmission delay. Moreover, we compare the proposed architecture with electrical NoCs and alternative ONoC architectures under various traffic patterns.

Yen-BSR: A New Approach for the Choice of Routes in WDM Networks

AbstractIn this paper we propose to use an iterative algorithm for optimizing the fixed-alternate shortest path routing in the dynamic routing and wavelength assignment (RWA) problem in wavelength routing optical networks. The algorithm performance is compared, in terms of blocking probability, with the Dijkstra and Yen traditional algorithms, as well as with the recently proposed best among the shortest routes (BSR) algorithm. The results suggest that it is feasible to choose an appropriate set of routes for each pair of nodes (source, destination), among the shortest paths and efficiently balance the network load. For all studied scenarios, the proposed heuristic achieved superior performance.

Optical Networking With Variable-Code-Rate Transceivers

We evaluate the impact of variable-code-rate transceivers on cost, capacity and survivability of wavelength-routed optical networks. The transmission rate and reach trade-off is quantified for two hypothetical coded modulation schemes (aggressive and conservative) in a wavelength routing network with 50-GHz-spaced channels. The aggressive scenario assumes the 64-QAM modulation format, a small gap to capacity, and a small excess bandwidth. The conservative scenario considers the 16-QAM modulation format, and a larger capacity gap and excess bandwidth. The performance of the conservative and aggressive technologies is evaluated in three representative networks. Transparent reaches are calculated by means of an existing analytical method which assumes the AWGN hypothesis for the nonlinear noise. It is shown that variable-code-rate transceivers enable the concept of soft protection, in which the protection lightpath operates at a data rate which is lower than the corresponding working lightpath, in a way to avoid regeneration. This is specially attractive in the transport of IP traffic, where capacity reduction (in average up to 25%) may be tolerable during a repair time. It is also shown that variable-code-rate transceivers have the potential to offer significant savings in terms of transceiver usage and wavelength occupation, when compared to current fixed-rate transceivers operating at 100, 200 or 400 Gb/s. Finally, practical variable-code-rate transceivers may achieve a discrete set of N code rates, yielding a quantized capacity-versus-reach curve. The system impact of N is evaluated for several network scenarios.

Estimating the blocking probability in wavelength-routed optical networks

In this work, a new methodology to compute the blocking probability in wavelength-routed optical networks is presented. The proposal is based on an interactive procedure, named Interactive Matrix Methodology (IMM), that executes actualization of the network traffic distribution in order to reach a precise blocking performance. The IMM updates an initial network link load continuously and computes the blocking probability for each output link considering that the traffic among the links is dependent and related with all links and nodes in the network, not only with all links in a given path or route. The simulation results obtained in the same conditions and in several optical network scenarios match very well with the theoretical approximation achieved with this methodology. The advantage of this theoretical methodology is to be fast, accurate and applicable in low load regions, where a discrete event simulation is not precise. Furthermore, this method can be used to compute the estimative of blocking probabilities per node and in the network, including the cases where the number of wavelengths is different on each node.

Multihop All-to-all Broadcast in WDM Optical Hypercube and Cube-connected Cycle

All-to-all broadcast is to disseminate a unique message from each node to every other node in the network. This is a fundamental problem in multiprocessor systems and telecommunication networks that need to collect information about other nodes in the network regularly in order to manage network resources efficiently. This paper addresses the problem of all-to-all broadcast communication in wavelength-routed optical hypercube and cube-connected cycle networks under multihop routing. In a multihop routed network, a message undergoes multiple Optical-Electrical-Optical conversions before reaching its destination. The multihop intermediate nodes (except the source and destination nodes) of a lightpath convert the optical signal into electrical signal, process the message, and then convert the message back to the optical form to transmit in the next optical hop. An optical hop is a continuous lightpath with no wavelength conversion. An upper bound on the number of wavelengths required to establish all-to-all broadcast is derived for hypercube and cube-connected cycle networks under multihop routing.

A Cognitive Quality of Transmission Estimator for Core Optical Networks

We propose a cognitive Quality of Transmission (QoT) estimator for classifying lightpaths into high or low quality categories in impairment-aware wavelength-routed optical networks. The technique is based on Case-Based Reasoning (CBR), an artificial intelligence technique which solves new problems by exploiting previous experiences, which are stored on a knowledge base. We also show that by including learning and forgetting techniques, the underlying knowledge base can be optimized, thus leading to a significant reduction on the computing time for on-line operation. The performance of the cognitive estimator is evaluated in a long haul and in an ultra-long haul network, and we demonstrate that it achieves more than 98% successful classifications, and that it is up to four orders of magnitude faster when compared with a non-cognitive QoT estimator, the Q-Tool.

Review and Performance Analysis on Routing and Wavelength Assignment Approaches for Optical Networks

For the past several years, traffic especially, Internet traffic has been increased tremendously and this growth demands for a high-speed communication network such as optical network. Routing and Wavelength Assignment (RWA) is one of the key tasks for the optical network, due to its information transparency and wavelength reuse characteristics. In this paper, we discuss different conventional RWA approaches in the wavelength-routed optical networks and compare them with our proposed Priority-based RWA (PRWA) scheme under wavelength continuity constraint. The performance analysis of different conventional RWA approaches including our PRWA scheme is conducted in terms of blocking probability. Finally, we address a number of research issues that appear to us to be both important and challenging.