Analysis of Optical Networks With Heterogeneous Grooming Architectures

We study the blocking probability and performance of single‐fiber and multifiber optical networks with wavelength division multiplexing (WDM). We extend the well‐known analytical blocking probability model by Barry and Humblet to the general model, which is proposed for both single‐fiber and multifiber network paths with any kind of wavelength conversion (no, limited, or full wavelength conversion) and for uniform and nonuniform link loads. We investigate the effect of the link load, wavelength conversion degree, and the number of wavelengths, fibers, and hops on blocking probability. We also extend the definition of the gain of wavelength conversion by Barry and Humblet to the gain of performance, which is fully general. Thanks to this definition and implementation of our model, we compare different WDM node architectures and present interesting results.

Optical networks can benefit from multipath routing by routing traffic over diverse fiber links to fulfill bandwidth requirements, balance network load and improve resource utilization. This paper focuses on the effectiveness of multipath routing on aggregating residual bandwidth of the established lightpaths using dynamic traffic grooming. An optimization model based on Integer Linear Programing (ILP) is formulated to leverage multipath routing and grooming to serve connection requests with known duration, in a scenario where the dynamic traffic can demand bandwidth either larger or smaller than a single wavelength capacity. The impact of a balancing policy, referred to as Holding Time Balancing (HTBalancing), on multipath routing with traffic grooming in optical networks is also investigated. Numerical results show that the proposed optimization model can achieve a lower bandwidth blocking and a better load balancing with HTBalancing policy, when compared with single path routing. The proposed relaxation algorithm can effectively find near optimal solutions, and be applied in realistic scenarios.

WDM Network Issues: QOT Impairments, Dynamic Bandwidth Allocation, Modeling and Monitoring Schemes based on ML

In this paper, we propose a parallel multiobjective approach based on the honey bees' behaviour for grooming low-speed traffic requests onto high-capacity optical channels. This problem of grooming low-speed traffic requests is known in the literature as the traffic grooming problem. This problem in mesh optical networks is an NP-hard problem, in which the solution time raises exponentially when the network size increases; therefore, the use of metaheuristics and parallelism jointly is a great option in order to reduce the prohibitive runtime. The parallel approach is implemented for shared-memory architectures by using OpenMP. In our experiments, we have measured the speedup and efficiency of the method with 1, 2, 4, 8 and 16 cores when dealing with three optical networks: small (6-node network, 6 nodes), medium (National Science Foundation, 14 nodes) and large (Nippon Telegraph and Telephone, 55 nodes). Furthermore, we present a comparative study with traditional methods and other multiobjective metaheuristics published in the literature; in which we show the advantages of our multiobjective proposal.

Traffic grooming in optical networks is the process of multiplexing and demultiplexing low-speed traffic streams onto high-speed wavelengths. The research in the domain of traffic grooming mainly focuses on minimizing number of SONET add/drop multiplexers (SADMs) in SONET/WDM rings and it has been shown that they can potentially be reduced by careful assignment of low-speed traffic streams onto high-speed wavelengths. However, the cost of the network not only depends on the number of SADMs, but also the number of wavelengths and the grooming ratio. It is often the case that all of them cannot be minimized simultaneously. In this article, the problem of minimization of cost of a SONET/WDM unidirectional ring has been modeled as a multiobjective optimization problem which simultaneously minimizes the number of SADMs, the number of wavelengths, and the grooming ratio. A popular multiobjective genetic algorithm (NSGA-II) has been used as the underlying optimization tool. The resultant set of near-Pareto-optimal solutions contains a number of nondominated solutions, which the user can judge relatively and pick up the most promising one according to the problem requirements. Performance of the proposed algorithm has been demonstrated on different network topologies.

Less attention has been given to energy aware optical counterparts, compared to the research in energy-aware wireless and ethernet networks. In this paper, we consider energy-aware traffic grooming problems in optical networks for both static and dynamic cases. Rather than simply considering a logical architecture of an optical node, we specifically look further into the modular physical architecture. We show that by reusing already active physical components during request allocations, we can significantly reduce the total number of active components and, hence, total energy consumption in the network, especially when traffic load is low. Since energy usage is an important element of operational expenditure, this approach provides the financial motivation for service providers along with the desired environmental motivation. We present a mathematical formulation of the problems, propose auxiliary graph based heuristics, and justify our cases compared to traditional approaches, based on simulation results.

Traffic Grooming in optical networks is one if the most important and hot problems in the area of optical network. In the static traffic grooming problem, we introduce the concept of QoS (Quality of Service); in order to minimize the network cost utilization rate and to maximize the QoS degree of the users at the same time, we apply the intelligent computing algorithm -QIA( the quantum-based Immune Algorithm) to the framework to solve the problem.

A multiobjective evolutionary algorithm based on decomposition with normal boundary intersection for traffic grooming in optical networks

The manycast communication paradigm is becoming increasingly important in today’s optical networks, wherein connection requests from a source node can be routed to a subset of a candidate destination set. This flexibility in choosing different destinations from a larger candidate destination set helps improve the network performance. In this paper, we develop a new analytical model to compute the network-wide blocking performance for generalized manycast routing and wavelength assignment (MRWA) in optical wavelength division multiplexed (WDM) networks. Specifically, we calculate the request blocking on full-wavelength convertible optical networks based on Markov chains and conditional probability analysis. Performance results show that our model is accurate and is verified by extensive simulation results.

We study the problem of providing real-time service to hard and soft real-time messages in wavelength division multiplexing (WDM) optical networks. We propose and evaluate a set of scheduling algorithms which schedule message transmissions in single-hop WDM passive star networks based on specific time constraints. We compare the performances of our algorithms with that of the typical WDM scheduling algorithm which does not consider the time constraint of the transmitted messages by discrete-event simulations and an analytical model. We find that the improvement on real-time performance can be attributed to our scheduling algorithms where the time constraint of messages has been taken into consideration. This study suggests that when scheduling real-time messages in WDM networks, one has to consider not only the problem of resources allocation in the network but also the problem of sequencing messages based on their time constraints.

We study the problem of allocating optical bandwidth to sets of communication requests in all–optical networks that utilize Wavelength Division Multiplexing (WDM). WDM technology establishes communication between pairs of network nodes by establishing transmitter–receiver paths and assigning wavelengths to each path so that no two paths going through the same fiber link use the same wavelength. Optical bandwidth is the number of distinct wavelengths. Since state–of–the–art technology allows for a limited number of wavelengths, the engineering problem to be solved is to establish communication between pairs of nodes so that the total number of wavelengths used is minimized; this is known as the wavelength routing problem. In this paper we survey recent advances in bandwidth allocation in tree–shaped WDM all–optical networks. We present hardness results and lower bounds for the general problem and the special case of symmetric communication. We give the main ideas of deterministic greedy algorithms and study their limitations. We demonstrate how we can achieve optimal and nearly–optimal bandwidth utilization in networks with wavelength converters using simple algorithms. We also present recent results about the use of randomization for wavelength routing.

In this letter, we propose a computational model for calculating blocking probabilities of multifiber wavelength division multiplexing (WDM) optical networks. We first derive the blocking probability of a fiber based on a Markov chain, from which the blocking probability of a link is derived by means of conditional probabilities. The blocking probability of a lightpath can be computed by a recursive formula. Finally, the network-wide blocking probability can be expressed as the ratio of the total blocked load versus the total offered load. Simulation results for different fiber-wavelength configurations conform closely to the numerical results based on our proposed model, thus demonstrating the feasibility of our proposed model for estimating the blocking performance of multifiber WDM optical networks.

There is a rapidly increasing data flow between sensors and on-board processors in avionic platforms. Electro-optic (EO) sensors are moving to hyperspectral and radar to phased array to enable precision targeting, wide field of view surveillance and navigation. These trends call for next generation optical network technology which has to provide increasing high speed data transmission under harsh conditions. Recent developments go beyond simple point-to-point fiber links towards establishing optical distribution networks to deal with the data traffic [1]. A flexible and potentially low-cost implementation is the passive optical network (PON) which scales easily to increasing needs simply by upgrading the peripheral units without need to change the fiber connections and infrastructure. PONs are well established in the commercial access market with the increasing push to fiber-to-the-home (FTTH) technologies which has led to the development of a variety of low-cost devices for these networks. A key enabler in our development of an avionics PON is the reflective semiconductor optical amplifier (RSOA) which combines amplification and modulation into a single device [2]. The RSOA is a non-resonant device, thus wideband with the potential for ruggedness, especially high temperature operation with small or no need for cooling. At higher data rates up to 20 Gbps a related device, the reflective electro-absorption modulator with integrated amplification (R-SOA-EAM) can be used instead. To complete the adaptation we replaced the laser, commonly used to provide optical input power in a PON architecture with another non-resonant device, the superluminescent LED (SLED). To create upgrade flexibility we utilized wavelength division multiplexing (WDM) which allows addition and subtraction of channels without changing hardware. Coarse WDM (CWDM) was chosen over Dense WDM (DWDM) for two reasons: the large channel width (20nm) of CWDM reduces cost by relaxing fabrication tolerance and renders the use of temperature control unnecessary, thereby increasing reliability. The concept and current state of development of our optical network is described in this paper.

Wavelength Division Multiplexing (WDM) has been widely used for studying the performance of optical networks, especially those employing optical passive star couplers. Many models have been proposed for WDM on an optical passive star coupler, such as each station equipped with a single tunable transmitter and a single fixed wavelength receiver, and each station with multiple tunable transmitters and multiple tunable receivers. The current technology only allows the transceivers to be tunable in a small range, a fact ignored in previous studies. In this paper, we focus on the design of WDM optical passive star networks with tunable transmitters of limited tuning range and fixed wavelength receivers. The limited tuning range has effects on the maximum delay, the total number of wavelengths which can be used, and the topological embedding. Complete graphs, meshes, and hypercubes are the three topologies studied in this paper. The relationship between the total number of wavelengths which can be utilized and the embedded topology is established. The bound for the maximum delay is analyzed. The optimal embedding algorithms are given for the systems embedded with one of the three topologies.

In anycast, connection requests are routed to one of multiple destination candidates, thus helping improve the overall acceptance of service requests in the network when compared to traditional unicast. In this paper we develop a new analytical model to compute the network-wide blocking performance for anycast routing and wavelength assignment (ARWA) in wavelength division multiplexing (WDM) optical networks using the reduced-load fixed-point approximation analysis. This model is based on conventional queuing theory for loss systems combined with a joint probability analysis of the anycast service alternatives. Performance results show that our model provides good accuracy compared to simulation results.