European Optical Network Research Articles

Improved spectral allocation in optical wireless communication based on quadrature amplitude modulation using metaheuristic wavelength division multiplexing

With the current surge in interest in high-speed wireless access to wireless communication data networks, appealing, and OFDM (Orthogonal frequency-division multiplexing) for achieving high data speeds. This research ends the real-time exception by proposing a larger number of subcarriers at 35 km/h data rates based on wireless communication as well as spectrum assignment approach is proposed. Simultaneous transmission has also been achieved using OFDM-QAM (Quadrature Amplitude Modulation). As a direct result of comparing, it to the signal delivered, a bit-error-rate performance calculation comparison has been done. The experimental analysis has been carried out for National Science Foundation Network (NSFNET) and EON (European Optical Network)− 28 network topology in terms of SNR, energy efficiency, Throughput and spectral efficiency. For National Science Foundation Network (NSFNet) topology the obtained SNR of 72 %, energy efficiency of 95 %, throughput of 96 % and spectral efficiency of 92 % and EON-28 topology of the network, the proposed technique obtained 70 % SNR, 92 % energy efficiency, 97 % throughput and 95 % spectral efficiency.

Associating machine-learning and analytical models for quality of transmission estimation: combining the best of both worlds

By associating machine learning and an analytical model (i.e., the Gaussian noise model), we reduce uncertainties on the output power profile and the noise figure of each amplifier in an optical network. We leverage the signal-to-noise ratio (SNR) of all the light paths of an optical network, monitored in all the coherent receivers. The learning process is based on a gradient-descent algorithm where all the uncertain input parameters of the analytical model are iteratively modified from their estimated values to match with the SNR of light paths in a European optical network. The design margin is then reduced to 0.1 dB for new traffic demands.

Solving routing and spectrum allocation problems in flexgrid optical networks using pre-computing strategies

Flexible optical network architectures are considered a very promising solution where spectrum resources are allocated within flexible frequency grids. This paper presents a minimum spectrum utilization (SU) and average path length (APL) approach to solve the (off-line) routing and spectrum allocation problem (RSA) based on combining a simple ordering pre-computation strategy, namely most subcarriers first (MSF) with three nature-inspired algorithms. These algorithms are ant colony optimization, differential evolution based relative position indexing (DE-RPI), and differential evolution general combinatorial (DE-GC). We begin by showing that MSF is the most effective ordering pre-computation strategy when compared to other well-known typical heuristics in the literature, such as first-fit, and longest path first. Then, we apply MSF in combination with the three nature-inspired algorithms to simultaneously optimize the SU and APL. The usefulness of MSF ordering pre-computation strategy is presented via a comparison of results obtained when using and not using MSF under the same scenarios. The algorithms are evaluated in benchmark optical networks, such as the NSFNet, the European optical network, and the 40-node USA network. We show that DE-RPI with MSF ordering pre-computation is the best option to solve the RSA problem, obtaining an average improvement percentage in the range of 0.9772–4.4086% on the SU and from $$-0.1668$$ to 0.8511% on the APL when compared to other meta-heuristics, either with or without the MSF ordering policy.

Resource Allocation for Elastic Optical Networks Using Geometric Optimization

Resource allocation with quality of service constraints is one of the most challenging problems in elastic optical networks that is normally formulated as a mixed-integer nonlinear optimization program. In this paper, we focus on novel properties of geometric optimization and provide a heuristic approach for resource allocation that is much faster than its mixed-integer nonlinear counterpart. Our heuristic consists of two main parts for routing/traffic ordering and power/spectrum assignment. It aims at minimization of the transmit optical power and spectrum usage constrained to the quality of service and physical requirements. We consider three routing and three traffic ordering procedures and compare them in terms of total transmit optical power, total received noise power, and total nonlinear interference including self- and cross-channel interferences. We propose a posynomial expression for the signal-to-noise ratio in which fiber nonlinearities and amplified spontaneous emission noise have been addressed. We also propose posynomial expressions that relate the modulation spectral efficiency to its corresponding minimum required signal-to-noise ratio. We then use the posynomial expressions to develop six geometric formulations for the power/spectrum assignment part of the heuristic that are different in run time, complexity, and accuracy. Simulation results demonstrate that the proposed solution has very good accuracy and much lower computational complexity in comparison with mixedinteger nonlinear formulation. As an example, for the European Cost239 optical network with 126 transmit transponders, the geometric formulation can be more than 22 times faster than its mixed-integer nonlinear counterpart. Numerical results also reveal that, in long-haul elastic optical networks, considering the product of the number of common fiber spans and the transmission bit rate is a better goal function for routing/traffic ordering that can reduce the total transmit optical fiber (total accumulated noise and nonlinear interference) up to 20% (15%).

Differential evolution optimization applied to the routing and spectrum allocation problem in flexgrid optical networks

Flexible optical network (FON) architectures are considered a very promising solution where spectrum resources are allocated within flexible frequency grids. Routing and spectrum allocation (RSA) in FON is an NP-complete problem. So far, this problem has been optimally solved for small instances with integer linear programming and has been suboptimally solved for more realistic instances by heuristic strategies. In this paper, we introduce the application of differential evolution (DE) to the off-line RSA problem in flexible optical networks. To the best of our knowledge, our work is the first application of a DE algorithm to the RSA problem. We develop two DE permutation-based algorithms named DE general approach (DE-GC) and DE relative position index (DE-RPI). Comparative studies show that in many cases, DE outperforms many other well-known evolutionary computational approaches. Furthermore, the method typically requires few control parameters. An illustrative example of the application of the DE-based algorithms is presented, and then, different heuristics are compared against the DE-RSA algorithms. Algorithms are evaluated in different test bench optical networks, such as the NSFnet and the European optical network, and for networks up to 40 nodes, such as the USA and Japan networks. Moreover, the DE-based algorithms save up to 37 % of spectrum utilization for the NSFnet and 13 and 15 % for the USA and Japan networks, respectively.

A novel algorithm to integrate synchronous digital hierarchy networks into Optical Transport Network using mixed line rates

In this era of high data transfer speeds and new age technologies, Optical Transport Network (OTN) along with its newly introduced Optical Transport Hierarchy (OTH) has provided a lease of life to legacy low rate networks. It has provided a common backbone for multiple data rates to coexist on same fiber along with the enhanced transmission reach. The cost effective Optical Transport Network design has always been a complex issue due to the presence of multiple variables like number of fibers on each link, available data rates on each fiber, the wavelength count, transmission reach at each data rate, etc. In this paper an Integer Linear Programming (ILP) model has been presented to solve Routing problem for Synchronous Digital Hierarchy (SDH) over OTN over DWDM design. Optical Transport Hierarchy (OTH) has been used to integrate heterogenous SDH/SONET operating at different rates (STM-16, STM-64 and STM-256) into a single network supporting mixed line rates. These rates can coexist in a same fiber but each rate carries different cost with it. The objective function aims at finding the least cost routing solution by looking at different tradeoffs between the Capital Expenditure and the operational expenditure. Certainly different variables like the number of fibers and wavelengths, transmission reach, etc. are a factor in it. A mechanism has been put to monitor the Bit Error Rate (BER) levels as well. For evaluating the ILP model, 18 Node 38 Link European Optical Network was considered as the reference model and two ordering techniques, namely, full ILP and highest rate first (HRF) were used for deriving the results. The ILP model was designed with minimum of decision variables so in spite of big reference network it converges much faster. Under the given conditions, full ILP gave least cost network whereas HRF ordering took least time for ILP to converge.

A heuristic algorithm for lightpath scheduling in next-generation WDM optical networks

We study the routing and wavelength assignment (RWA) problem of scheduled lightpath demands (SLDs) in all-optical wavelength division multiplexing networks with no wavelength conversion capability. We consider the deterministic lightpath scheduling problem in which the whole set of lightpath demands is completely known in advance. The objective is to maximize the number of established lightpaths for a given number of wavelengths. Since this problem has been shown to be NP complete, various heuristic algorithms have been developed to solve it suboptimally. In this paper, we propose a novel heuristic RWA algorithm for SLDs based on the bee colony optimization (BCO) metaheuristic. BCO is a newborn swarm intelligence metaheuristic approach recently proposed to solve complex combinatorial optimization problems. We compare the efficiency of the proposed algorithm with three simple greedy algorithms for the same problem. Numerical results obtained by numerous simulations performed on the widely used realistic European Optical Network topology indicate that the proposed algorithm produces better-quality solutions compared to those obtained by greedy algorithms. In addition, we compare the results of the BCO---RWA---SLD algorithm with four other heuristic/metaheuristic algorithms proposed in literature to solve the RWA problem in the case of permanent (static) traffic demands.

Enhanced just-in-time plus protocol for optical burst switching networks

We propose a new one-way resource reservation protocol for optical burst switching OBS networks, called Enhanced Just-in-Time Plus E-JIT + . The protocol is described in detail, and its formal specifi- cation is presented, following an extended finite state machine approach. The performance evaluation of E-JIT + is analyzed in comparison with other proposed OBS protocols JIT + and E-JIT for the following network topologies: rings; degree-two, degree-three, and degree-four chordal rings; mesh-torus; NSFNET; ARPANET; FCCN-NET; and the European Optical Network. We evaluate and compare the performance of the dif- ferent protocols in terms of burst loss probability, taking into account the most important OBS network parameters. It was shown that E-JIT + per- forms better than available one-way resource reservation protocols for all the evaluated network topologies. Moreover, the scalability of E-JIT + was observed, and when the network traffic increases, the burst loss probability also increases, leading to a worse network performance. © 2010 Society of Photo-Optical Instrumentation Engineers. DOI: 10.1117/1.3462048 Subject terms: Enhanced Just-In-Time Plus; Enhanced-JIT; optical burst switching; resource reservation protocol; performance.

Adaptive Schemes for Differentiated Availability-Aware Connection Provisioning in Optical Transport Networks

In this paper, we present two adaptive schemes, namely, global differentiated availability-aware provisioning (G-DAP) and link-by-link differentiated availability-aware provisioning (LBL-DAP) for connection provisioning in optical transport networks under dual failure assumption. G-DAP attempts to determine a feasible sharing degree for each availability class for the links in the network globally. As an enhancement to G-DAP, LBL-DAP tries to determine a feasible sharing degree per availability class on each link. Connections belong to one of the five availability classes with the availability requirements of 0.98, 0.99, 0.999, 0.9999, and 0.99999, which are specified in their service level agreement (SLA). We compare the performance of the proposed schemes with a conventional service provisioning scheme, compute a feasible solution (CAFES) under the NSFNET and European optical network (EON) topologies. The simulation results show that the proposed schemes introduce better availability per connection and lower blocking probabilities. LBL-DAP performs the best by monitoring the shareability status of each link periodically with respect to the metrics studied, and decreases resource overbuild.

Performance Implications of Meshing Degree for Optical Burst Switched Networks Using One-Way Resource Reservation Protocols

This paper discusses performance implications of meshing degree (or nodal degree) for optical burst switching (OBS) mesh networks using one-way resource reservation protocols. The analysis is focused on the following topologies: rings, chordal rings with nodal degrees ranging from three to six, mesh-torus, NSFNET, ARPANET and the European Optical Network (EON). It is shown that the largest nodal degree gain, due to the increase of the nodal degree from two to around three, is observed for degree-three chordal ring topology, where as the smallest gain is observed for the ARPANET. For these cases, the magnitude of the nodal degree gain is slightly less than three orders for the degree-three chordal ring and less than one order of magnitude for the ARPANET. On the other hand, when the nodal degree increases from two to a value ranging from about four up to six, the nodal degree gain ranges between four and six orders of magnitude for chordal rings. However, EON, which has a nodal degree slightly less than four has the smallest nodal degree gain. The observed gain for this case is less than one order of magnitude. Since burst loss is a key issue in OBS networks, these results clearly show the importance of meshing degree for this kind of networks.

A binary (0-1) linear program formulation for the placement of limited-range wavelength converters in wavelength-routed WDM networks

We investigate the problem of optimally placing limited-range wavelength converters at a subset of nodes in wavelength-routed wavelength-division-multiplexing (WDM) networks. We consider two different aspects of the converter-placement problem: 1) the placement minimizing the network-wide blocking probability; and 2) the placement minimizing the number of wavelength-convertible nodes to meet the performance constraints. We present a binary (0-1) linear program (BLP) formulation in which the end-to-end blocking probability is expressed as a linear function of converter locations so that standard linear program (LP) optimization packages can be employed to obtain the optimal solution of the problems. We also present a new analytical model for estimating the end-to-end blocking probabilities. Experiments have been conducted over four network topologies, including 19-node European optical network (EON), 24-node USA backbone network (UBN), 32-node HYPERCUBE, and 36-node MESH-TORUS. We demonstrate that the optimal solutions of the converter-placement problems can be obtained within a reasonable computation time.

A heuristic for placement of limited range wavelength converters in all-optical networks

Wavelength routed optical networks have emerged as a technology that can effectively utilize the enormous bandwidth of the optical fiber. Wavelength converters play an important role in enhancing the fiber utilization and reducing the overall call blocking probability of the network. As the distortion of the optical signal increases with the increase in the range of wavelength conversion in optical wavelength converters, limited range wavelength conversion assumes importance. Placement of wavelength converters is a NP complete problem [K.C. Lee, V.O.K. Li, IEEE J. Lightwave Technol. 11 (1993) 962–970] in an arbitrary mesh network. In this paper, we investigate heuristics for placing limited range wavelength converters in arbitrary mesh wavelength routed optical networks. The objective is to achieve near optimal placement of limited range wavelength converters resulting in reduced blocking probabilities and low distortion of the optical signal. The proposed heuristic is to place limited range wavelength converters at the most congested nodes, nodes which lie on the long lightpaths and nodes where conversion of optical signals is significantly high. We observe that limited range converters at few nodes can provide almost the entire improvement in the blocking probability as the full range wavelength converters placed at all the nodes. Congestion control in the network is brought about by dynamically adjusting the weights of the channels in the link thereby balancing the load and reducing the average delay of the traffic in the entire network. Simulations have been carried out on a 12-node ring network, 14-node NSFNET, 19-node European Optical Network (EON), 28-node US long haul network, hypothetical 30-node INET network and the results agree with the analysis.

Impact of wavelength converters in wavelength routed all-optical networks

This paper attempts to study the impact of wavelength converters in WDM wavelength routed all-optical networks. A new heuristic approach for placement of wavelength converters to reduce blocking probabilities is explored. Multihop virtual topology is designed to minimize the number and overall cost of the converters. Blocking probabilities for Static Lightpath Establishment (SLE) and Dynamic Lightpath Establishment (DLE) are analyzed. In the case of SLE, arranging lightpaths in ascending order of their path length reduces blocking probability. Wavelength converters placed at nodes with high nodal degree further reduces the blocking probabilities. Simulation studies performed on 28-node USA long haul network, 20-node arbitrary mesh network, and 19-node EON (European Optical Network) validate the observations made earlier.

Toward wide-scale all-optical transparent networking: the ACTS optical pan-European network (OPEN) project

The European ACTS project optical pan-European network (OPEN) aims at assessing the feasibility of an optical pan-European overlay network, interconnecting major European cities by means of a mesh of high-capacity optical fiber links, cross-connected through transparent photonic nodes. Both the transmission links and the routing network elements rely on wavelength division multiplexing (WDM) all-optical technologies, such as wavelength translation. This paper presents results obtained in the following domains covered within the project: network topology considerations (optimization and dimensioning); network physical layer simulation; fabrications of packaged functional modules based on advanced optoelectronic devices; laboratory demonstrations of N/spl times/10 Gb/s transmission and routing; feasibility of an optical time division multiplexing/WDM (OTDM/WDM) interface; and the field implementation of a 4/spl times/4 multiwavelength crossconnect prototype, featuring all-optical space and wavelength routing. This implementation was realized in two cross-border field trials, one conducted between Norway and Denmark and the other between France and Belgium. The final results of the Norway to Denmark field trials are presented, featuring the successful cascade of three wavelength-translating optical crossconnects (OXCs), along with the transmission over 1000 km of a mix of standard/submarine cable links for four channels at 2.5 Gb/s.

Approach to the scalability of a European multiwavelength multihop optical network

Approach to the scalability of a European multiwavelength multihop optical network

Survivable European optical transport network: capacity evaluation

The feasibility of a survivable all-optical transport network over standard single-mode fibre between eight major European cities is investigated. The chosen topology is intended to ensure survivability after a link or a node failure. The maximum transmission rate, limited by fibre dispersion, is estimated for three topologies and two modulation schemes: chirp-free intensity modulation and dispersion supported transmission. The network capacity is evaluated at 662 Mbit s-1 and 2.5 Gbit s-1.

The design of a European optical network

This paper presents a number of design issues under consideration in the development of an all-optical network linking major centers in Europe. The proposed network is characterized by spanning a large geographical area, the diameter is in excess of 3000 km, but with a relatively small number of nodes (20). The study combines aspects of two optical network projects funded by the European Commission: COST 239-ultra-high capacity optical transmission networks and RACE 2028: multiwavelength transport network. The network uses multiwavelength technology and combines wavelength selection and space switching to achieve signal routing. One of the objectives of the study is to understand the extent to which transparency can be achieved in such a large network. For example the effect of using amplifiers to achieve transparency is to provide extremely long fiber paths in which non-linear effects may become significant and effectively limit the number of wavelengths that can be employed; this limit may be at conflict with the number of wavelengths required from a traffic viewpoint. The paper therefore considers capacity requirements, transmission limitations and node and network architecture issues. It is concluded that partitioning of the network may be necessary to maximize transparency and suggestions are made as to how this might be achieved. >