The advances in fiber optics and wavelength division multiplexing (WDM) technology are viewed as the key to satisfying the data-driven bandwidth demand of today’s Internet. The mismatch of bandwidths between user needs and wavelength capacity makes it clear that some multiplexing should be done to use the wavelength capacity efficiently, which will result in reduction on the cost of line terminating equipment (LTE). The technique is referred to as traffic grooming. Previous studies have concentrated on different objectives, or on some special network topologies such as rings. In our study, we aim at minimizing the LTE cost to directly target on minimizing the network cost. We look into the grooming problem in elemental topologies as a starting point. First, we conduct proofs to show that traffic grooming in path, ring and star topology networks with the cost function we consider is NP-Complete. We also show the same complexity results for a Min-Max objective that has not been considered before, on the two elementary topologies. We then design polynomialtime heuristic algorithms for the grooming problem in rings (thus implicitly paths) and stars for networks of larger size. Experiments on various network sizes and traffic patterns

Abstract—We consider the role of switching in minimizing the number of electronic ports [e.g., synchronous optical network (SONET) add/drop multiplexers] in an optical network that carries subwavelength traffic. Providing nodes with the ability to switch traffic between wavelengths, such as through the use of SONET cross-connects, can reduce the required number of electronic ports. We show that only limited switching ability is needed for significant reductions in the number of ports. First, we consider architectures where certain “hub ” nodes can switch traffic between wavelengths and other nodes have no switching capability. For such architectures, we provide a lower bound on the number of electronic ports that is a function of the number of hub nodes. We show that our lower bound is relatively tight by providing routing and grooming algorithms that nearly achieve the bound. For uniform traffic, we show that the number of electronic ports is nearly minimized when the number of hub nodes used is equal to the number of wavelengths of traffic generated by each node. Next, we consider architectures where the switching ability is distributed throughout the network. Such architectures are shown to require a similar number of ports as the hub architectures, but with a significantly smaller “switching cost. ” We give an algorithm for designing such architectures and characterize a class of topologies, where the minimum number of ports is used. Finally, we provide a general upper bound on the amount of switching required in the network. For uniform traffic, our bound shows that as the size of the network increases, each traffic stream must be switched at most once in order to achieve the minimum port count. Index Terms—Optical networks, synchronous optical network (SONET), traffic grooming. I.

Abstract—In this paper, we study the benefits of using tunable transceivers for reducing the required number of electronic ports in wavelength-division-multiplexing/time-division multiplexing optical networks. We show that such transceivers can be used to efficiently “groom ” subwavelength traffic in the optical domain and so can significantly reduce the amount of terminal equipment needed compared with the fixed-tuned case. Formulations for this “tunable grooming ” problem are provided, where the objective is to schedule transceivers so as to minimize the required number of ports needed for a given traffic demand. We establish a relationship between this problem and edge colorings of graphs which are determined by the offered traffic. Using this relationship, we show that, in general, this problem is NP-complete, but we are able to efficiently solve it for many cases of interest. When the number of wavelengths in the network is not limited, each node is shown to only require the minimum number of transceivers (i.e., no more transceivers than the amount of traffic that it generates). This holds regardless of the network topology or traffic pattern. When the number of wavelengths is limited, an analogous result is shown for both uniform and hub traffic in a ring. We then develop a heuristic algorithm for general traffic that uses nearly the minimum number of transceivers. In most cases, tunable transceivers are shown to reduce the number of ports per node by as much as 60%. We also consider the case where traffic can dynamically change among an allowable set of traffic demands. Tunability is again shown to significantly reduce the port requirement for a nonblocking ring, both with and without rearrangements. Index Terms—Graph coloring, integer linear programming (ILP), optical networks, traffic grooming, wavelength-division multiplexing (WDM). I.

We consider the multi--objective optimization of a multi--service AWG--based single--hop metro WDM network with the two conflicting objectives of maximizing throughput while minimizing delay. We develop and evaluate a genetic algorithm based methodology for finding the optimal throughput--delay trade--o# curve, the so-- called Pareto--optimal frontier. Our methodology provides the network architecture (hardware) and the Medium Access Control (MAC) protocol parameters that achieve the Pareto--optima in a computationally e#cient manner. The numerical results obtained with our methodology provide the Pareto--optimal network planning and operation solutions for a wide range of tra#c scenarios. The presented methodology is applicable to other networks with a similar throughput--delay trade--o#.

Abstract — In this paper, we study the benefits of using tunable transceivers for reducing the required number of electronic ports in WDM/TDM networks. We show that such transceivers can be used to efficiently “groom ” sub-wavelength traffic in the optical domain and so can significantly reduce the number of electronic ports compared to the fixed tuned case. We provide a new formulation for this “tunable grooming ” problem. We show that in general this problem is NP-complete, but we are able to efficiently solve it for many cases of interest. When the number of wavelengths in the network is not limited, we show that each node only needs the minimum number of transceivers (i.e., no more transceivers than the amount of traffic that it generates). This holds regardless of the network topology or traffic pattern. When the number of wavelengths is limited, we show an analogous result for both uniform and hub traffic in a ring. We also develop a heuristic algorithm for general traffic that uses nearly the minimum number of transceivers. In most cases, tunable transceivers are shown to reduce the number of ports per node by as much as 60%. I.

Abstract — Traffic grooming, in which low-rate circuits are multiplexed onto wavelengths, with the goal of minimizing the number of add-drop multiplexers (ADMs) and wavelengths has received much research attention from the optical networking community in recent years. While previous work has considered various traffic models and network architectures, protection requirements of the circuits have not been considered. In this paper, we consider survivable traffic grooming, or grooming traffic which contains a mix of circuits that need protection and that do not need protection. We assume a unidirectional ring network with all-to-all symmetric traffic withØ�circuits between each node pair, of which×require protection. As it turns out, survivable traffic grooming presents a significant tradeoff between the number of wavelengths and the number of ADMs, which is almost non-existent in non-survivable traffic grooming for this type of traffic. We explore this tradeoff for some specific cases in this paper. We also present some new results and solution methods for solving certain nonsurvivable traffic grooming problems. Index Terms — Wavelength-division-multiplexing (WDM), traffic grooming, survivability, optical networks, ring networks, lightpaths, circuits, add-drop multiplexers, all-to-all traffic. I.