Wavelength-routed Networks Research Articles

DSP-based inter-channel interference monitoring in flexible wavelength-routed networks

The efficiency of optical networks employing flexible wavelength division multiplexing (WDM) can be increased by maximizing the throughput of each individual channel, provided that the position of its neighboring channel is known with sufficient accuracy in order to avoid inter-channel interference. In this paper, we propose a digital signal processing (DSP) algorithm, leveraging the use of an artificial neural network (ANN), to estimate the neighboring channels’ distance by processing raw digital samples from a standard coherent receiver. We present an efficient dataset design approach, based on Latin hypercube sampling (LHS), in order to effectively optimize and validate the algorithm under different assumptions on the optical WDM channels. We investigate the accuracy of the ANN-based DSP scheme through simulation analysis, highlighting its potential in relation to the characteristics of the optical network. Finally, we validate our approach in an experimental setup using standard commercial coherent transceivers. The experimental results show that the distance from the neighboring WDM channels can be estimated with a root mean square error of less than 1.5 GHz for a channel under test with a symbol rate of 52 GBaud.

Monolithically Integrated 8 × 8 Transmitter-Router Based on Tunable V-Cavity Laser Array and Cyclic Arrayed Waveguide Grating Router

A monolithic 8 × 8 transmitter-router chip fabricated on InGaAlAs-InP multi-quantum well wafer for distributed wavelength routing network in the O-band with a channel spacing of 400 GHz is experimentally demonstrated. A tunable V-cavity laser (VCL) array, a cyclic-arrayed waveguide grating router (AWGR) and a semiconductor amplifier (SOA) array are integrated using the quantum-well intermixing (QWI) technique for its fabrication simplicity and cost effectiveness. A 200 GHz-spaced compact-size VCL is demonstrated with a 27 nm tuning range and a side-mode suppression ratio (SMSR) around 40 dB using a single-electrode controlled tuning. The chip output power is 24.6 mW. Measurement results of the transmitter-router chip show that all 64 input-output combinations have cyclic response spectra. After passing through the SOA with 80 mA bias current, an output power of about 9.6 mW and optical signal-to-noise ratio (OSNR) up to 39 dB have been measured. The demonstrated transmitter-router chip is fabricated on the same quantum well structure without requiring multiple epitaxial growth and complex grating fabrication. The characteristics of multi-wavelength and multi-port transmissions enable the distributed optical routing networks with flexible bandwidth allocation, which can find wide application in datacenters and high-performance computers.

Data preprocessing for machine-learning-based adaptive data center transmission

To enable optical interconnect fluidity in next-generation data centers, we propose adaptive transmission based on machine learning in a wavelength-routing network. We consider programmable transmitters that can apply N possible code rates to connections based on predicted bit error rate (BER) values. To classify the BER, we employ a preprocessing algorithm to feed the traffic data to a neural network classifier. We demonstrate the significance of our proposed preprocessing algorithm and the classifier performance for different values of N and switch port count.

Wavelength-routed optical backbone network planning under fuzzy environment

Wavelength-routed optical backbone network planning under fuzzy environment

Design of Optoelectronic Hybrid Switching High Performance Computing Internet

Optoelectronic hybrid network technology is mixed with pure electric packet switching network, which can improve network capacity and reduce power consumption. However, the long configuration time and complex management of optical circuit switch affect the performance of optoelectronic hybrid network. Therefore, a new optoelectronic hybrid network architecture (BET) is designed. The network architecture consists of Ethernet electric packet switching network and optical wavelength routing network. The signal receiving and dispatching of optical routing network is realized by circular arrayed waveguide grating router. Based on the characteristics of wavelength cycling routing, there is no need to adjust the routing of optical signals to the destination port, that is, there is no need to configure the optical wavelength routing network. At the same time, an intelligent node dynamic reconfiguration (RG) algorithm is designed to improve the resource utilization of optical nodes. In this method, the network link utilization, cache occupancy, and network load are taken into account to adjust the distribution of optical nodes in the optoelectronic hybrid network. In the process of the experiment, by changing the message length, it is found that the optical wavelength routing network can achieve large capacity and new-type transmission and effectively reduce the delay at the same time; on the optoelectronic hybrid network, with the help of Hadoop platform, distributed cluster is built and used to transmit an XML data encoding (ED code), solve the finite state transducers (FST) and encode them. Compared with the traditional electric packet switching network, the transmission delay of ED code is greatly reduced after the introduction of optical circuit switch, and the efficiency of FST solution and coding calculation is improved by at least 30%.

Optoelectronic Hybrid Network Architecture and Its Performance Analysis

Optoelectrical hybrid network technology is introduced into a network based on pure electrical packet switching, which increases network capacity and reduces power consumption. However, the problems of long configuration time and complex management of optical circuit switches affect the performance of hybrid optoelectrical networks. A new type of hybrid optoelectronic network architecture (HOEP) cooperated by Ethernet packet switching network and optical wavelength routing network was designed in the study. The optical routing network transmitted and received optical signals by using a circular array waveguide grating router, and transmitted the optical signal carrying data to the target port based on the characteristics of wavelength cyclic routing. The entire process only needed to modulate the data signal, and did not need to configure the optical wavelength routing network. At the same time, in order to further improve the resource utilization of optical nodes, a kind of intelligent node dynamic reconstruction (RC) algorithm was designed. Combining with network link utilization, cache occupancy, and network load value, this method could dynamically adjust the usage distribution of optical nodes for reconstruction. During the experiment, the RC algorithm was applied to the HOEP network architecture. Compared with other typical network architectures, the HOEP network proposed in the study can effectively reduce the network cost, power consumption, and improve network throughput. Moreover, the introduction of RC algorithm and network equipment can make the cost remain within the controllable range, while it can further increase the network throughput and reduce the power consumption of the HOEP network, thereby meeting the dynamic demand for network bandwidth with larger data traffic.

Improving Fibre Optics Transmission with Wave Length Division Multiplex through Routed-Switching Network

The Optics Fiber link is implemented to satisfy various types of networks, with a wide range of transmission capabilities and improved speed in signal delivery. The link carries multiple signals and for adequate transmission, multiplexing of signals, each signal component, is aggregated and transmitted over a common link which is regarded as multiplexing. The wavelength-routed network bridges the gap of the timeshare, which has retardation on speed and efficiency. The wavelength division multiplex (WDM) is a multiplexing technique designed to suit fiber optics and achieves speed demands, as against time-division multiplexing(TDM) for analog continuous signals (CT) and frequency division multiplexing(FDM) for discrete-time signals(DT). The synchronous optical network (SONNET) and synchronous digital hierarchy (SDH) and the Asynchronous transfer mode (ATM) create an inter-switching system using various matrix dimensions, of 2 X 2, 8 X 8 and other multiples to achieve a versatile routing switching technique. Wavelength division Multiplex and it’s a dense modification (DWDM); have greatly improved the quality and speed of signal transmission over all other techniques.

Spatially and Spectrally Flexible Scheduling With Time-Slotted Lightpath-Switching

Optical wavelength-routed networks enable parallel transmission of massive datasets on nonover-lapping wavelength channels. However, as the sizes of scientific workflows increase, the availability of multi-wavelength resources will fall short of supporting application needs. Rather, these resources must be allocated intelligently, efficiently, and flexibly to bear the burden of high-volume science. We propose lightpath-switching to support modification to the set of wavelength/route resources used to carry and transmit a lightpath signal intermittently throughout its lifetime. Lightpath-switching exposes the scheduler to flexible consumption of unused, fragmented resources during the request schedule but requires neither underlying network technology nor equipment enhancement. We explore the efficacy of lightpath-switching in terms of wavelength-switching, path-switching, and a combination of the two techniques. We prove these problems are NP-complete and develop optimization models and efficient heuristics to quantitatively and qualitatively evaluate the solution space against optimality benchmarks. Our evaluations consider cross-dimension resource consumption from the time, space, and spectrum domains, and our findings indicate great potential for increasing network-wide resource savings, particularly via wavelength-switching. Furthermore, evidence is presented to defend the claim that spectral flexibility has a greater impact on resource utilization efficiency than spatial flexibility.

Sliding Scheduled Lightpath Establishment With Time-Slotted Wavelength-Switching

Extreme-scale transmissions exhibit schedules dependent upon the equipment used to generate data, availability of the collaborators who will investigate and analyze the data, and the availability of storage and supercomputing resources, which must be dedicated to distribution, backup, computation, and visualization of data. Given such a wide array of dependencies, these applications, which are often scientific in nature, offer the luxury of in-advance reservation of network resources prior to the demand uptimes. Advance reservation (AR) allows for efficient scheduling around or in cooperation with competing reservations from other applications. This work focuses on static inputs to two classifications of AR demands: with and without sliding-window flexibility. We further introduce the ability for a demand to be assigned to more than one dedicated wavelength at different points throughout its lifetime depending on availability. This λ-switching functionality is incorporated at time-slot granularity, which limits the overhead associated with reconfiguring wavelength resources at runtime and enhances opportunities for scheduling efficiency. A novel λ-switching integer linear program is presented to evaluate this enhancement under varying degrees of temporal flexibility. Detailed and novel proofs are provided, which demonstrate that AR scheduling with and without λ-switching is in the complexity class NP-complete. Conservative heuristics are presented to harness the benefits of λ-switching while lowering the trade-off from transceiver reconfiguration overhead. Lower bounds also are developed as a baseline comparison for these heuristics, and we evaluate these solutions through extensive simulation. We also introduce the notion of considering time-slotted, wavelength-routed networks from the perspective of a finer resource granularity represented by the intersection of the temporal and spectral resource domains.

Topology exploration of a thermally resilient wavelength-based ONoC

With the growing number of cores, high-performance systems face power challenges due to dominating communication power. Thus, attaining energy efficient high-bandwidth inter-core communication nominates photonic network-on chip as the most promising interconnection paradigm. Although photonic networks pave the way for extremely higher performance communications, their intrinsic susceptibility to thermal fluctuations intimidates reliability of system. This necessitates the development of methodologies to analyze and model thermal effects on network behavior. In this paper, we model temperature fluctuations of optical chips and analyze photonic networks in a holistic approach. We present a novel wavelength-routed all-optical mesh network-on-chip, which significantly reduces optical contention scenarios throughout the network. While leveraging slightly larger number of wavelengths, it attains tolerance against thermal-induced faults. Our proposed architecture is compared against a popular wavelength-routed network, i.e. λ-router, in terms of throughput, in the presence of temperature drifts. Moreover, reliability comparison addressing fault rate in terms of temperature variation reveals that our proposed architecture significantly outperforms λ-router, as its competitor.

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.

Graph-Model-Based Dynamic Routing and Spectrum Assignment in Elastic Optical Networks

In recent years, the concept of the elastic optical network (EON) was proposed and very quickly became an attractive solution for flexible channel bandwidth utilization. Analogous to the routing and wavelength assignment (RWA) problem in traditional wavelength-routed networks, routing and spectrum assignment (RSA) is the most basic and critical resource management issue in EONs. In this work, we exploit and modify the layered graph model, which is a well-known RWA model, to design two RSA heuristic algorithms named LG-FF and LG-SP. Additionally, we also derive an analytical model to estimate the number of required layered graphs. Numerical results demonstrate that LG-SP can achieve the same blocking performance level with significant time complexity reduction as compared to the near-optimal solution. Whether we care about blocking performance or aim at saving computational time, the layered graph is an important representation model of resource utilization status to efficiently solve the RSA problem.

Postcompensation of Nonlinear Distortions of 64-QAM Signals in a Semiconductor-Based Wavelength Converter

We experimentally investigate postcompensation of nonlinear distortions induced by a wavelength converter (WC) based on four-wave mixing in a semiconductor optical amplifier. The technique exploits a low-complexity digital filter-based backpropagation (DFBP) method. We perform postcompensation of nonlinear distortions following single stage wavelength conversion of 5 Gbd 64-quadrature amplitude modulation (QAM). We examine the DFBP performance in the presence of a degraded optical signal-to-noise ratio at the WC input, and explore the WC optimal operating conditions. Also, we experimentally demonstrate for the first time in the literature the dual stage wavelength conversion of QAM signals, in particular, 5 Gbd 64-QAM, and show that bit error rate below hard-decision forward error correction threshold is only possible with postcompensation of nonlinear distortions. These results are of importance for the development of wavelength-routed networks requiring successive wavelength conversion stages to enhance routing capabilities.

Embedding IP Unique Shortest Path Topology on a Wavelength-Routed Network: Normal and Survivable Design

In this paper, we address the network virtualization problem of embedding a unique shortest path-based IP topology using lightpaths in a wavelength-routed network. We present an integer linear programming formulation and propose a 2-phase heuristic approach to solve this problem. We extend the model and the heuristic by addressing survivability in an integrated cross-layer framework, where the objective is to allocate a light-path topology that remains connected in the event of any single physical link failure while providing the IP network with unique shortest paths for all node-pairs. We consider a number of measures to show effectiveness of our approach and to discuss the impact on normal and survivable topology design, in terms of the number of transreceivers deployed.

Scalable Design Method of Attractors in Noise-Induced Virtual Network Topology Control

One approach to accommodating IP traffic on a wavelength-routed network is to construct a virtual network topology (VNT) and reconfigure the VNT according to traffic changes. Our research group has proposed a VNT control method based on attractor selection, which is a model of the behavior by which living organisms adapt to unknown changes in their surrounding environment. Guided by attractors, the VNT control method searches for a solution: a VNT that can accommodate the IP traffic. Attractors are a subset of the equilibrium points in the solution space and correspond to VNT candidates. It is crucial to design the attractors properly, since they define the attractive states in the VNT control. If the VNT candidates are not designed properly, it takes a long time for the method to find a solution. This paper therefore proposes a method for designing VNT candidates. Our basic approach is to prepare VNT candidates in which the bottleneck links (lightpaths) are different from each other. However, our exhaustive algorithm based on this approach has the problem of requiring large amounts of computational time for large-scale networks. We therefore propose a method that hierarchically contracts a network topology to enable application of our algorithm to large-scale networks. Evaluation results show that the VNT control method using attractors obtained by our method achieves shorter convergence times.

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.

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.

WDM network and multicasting protocol strategies.

Optical technology gains extensive attention and ever increasing improvement because of the huge amount of network traffic caused by the growing number of internet users and their rising demands. However, with wavelength division multiplexing (WDM), it is easier to take the advantage of optical networks and optical burst switching (OBS) and to construct WDM networks with low delay rates and better data transparency these technologies are the best choices. Furthermore, multicasting in WDM is an urgent solution for bandwidth-intensive applications. In the paper, a new multicasting protocol with OBS is proposed. The protocol depends on a leaf initiated structure. The network is composed of source, ingress switches, intermediate switches, edge switches, and client nodes. The performance of the protocol is examined with Just Enough Time (JET) and Just In Time (JIT) reservation protocols. Also, the paper involves most of the recent advances about WDM multicasting in optical networks. WDM multicasting in optical networks is given as three common subtitles: Broadcast and-select networks, wavelength-routed networks, and OBS networks. Also, in the paper, multicast routing protocols are briefly summarized and optical burst switched WDM networks are investigated with the proposed multicast schemes.

Optical Network Management and Its Performance Evaluation for Both Future Cost Planning and Triple Play Solutions

This paper has presented the wavelength division multiplexing technology is being extensively deployed on point to point links within transport networks in the Egypt. Our suggested Trans-Egypt Network which uses optical cross connects to route lightpaths through the network are referred to as wavelength routing networks. The average setup time, average link utilization, traffic load, blocking probability, network costs, and network throughput with triple play solutions and achievable link utilization for multi math routing in the presence and absence of wavelength conversions are the major interesting parameters in the design of network topology under different routing and wavelength assignment such as first fit, random, least used and most used in order to upgrade network performance and its transmission efficiency.