Optimal Placement Of Wavelength Converters Research Articles

Wavelength Converter Based Optimized RWA for All Optical Networks

Wavelength converters are used in WDM networks to avoid call blocking and minimizing the blocking probability. Optimal placement of wavelength converters restricts the call blocking probability, the complexity and improves the overall network performance of the network. In this paper, we propose a new weight dependent routing and wavelength assignment algorithm for the optimal placement of the wavelength converters. The wavelength converter placement was considered separately at all the nodes and the partial nodes. Our algorithm outperforms the previously reported studies and requires a lesser number of wavelength converters to achieve the required performance. It reduces the blocking probabilities up to 5.4% and shows that the first four nodes primarily control the blocking performance of the network. The study also reveals that instead of merely increasing the number of converters, their placement at the right location plays a crucial role in improving the performance. Initially, although an increase in the number of the wavelengths also improves the network performance, the further increase does not contribute much to the reduction of the blocking probability.

Review of Physical Layer Related Issues in WDM Networks: Part-II

In the first part of this paper [1] we reviewed the non-linear effects present in the optical fiber, different types of optical amplifiers available, their limitations and the choice of amplifier for use in long haul WDM systems. It was shown that the number of amplifiers deployed is limited by the noise generated by the amplifiers. Also, the algorithms used for optimal placement of in-line amplifier had been discussed. In the design of the long haul WDM system, wavelength converters play a major role in reducing the blocking probability of the optical network. In this second and concluding part, we review the architecture of wavelength converters. We discuss various analytical models for evaluating blocking probabilities under different conditions and the routing and wavelength assignment schemes. We conclude with the summary of the various algorithms for optimal placement of wavelength converters.

On the optimal placement of wavelength converters in WDM networks

An important goal of the design of wavelength division multiplexing (WDM) networks is to use less wavelengths to serve more communication needs. According to the wavelength conflict rule, we know that the number of wavelengths required in a WDM network is at least equal to the maximal number of channels over a fiber (called maximal link load) in the network. By placing wavelength converters at some nodes in the network, the number of wavelengths needed can be made equal to the maximal link load. In this paper, we study the problem of placing the minimal number of converters in a network to achieve that the number of wavelengths in use is equal to the maximal link load. For duplex communication channels, we prove that the optimal solution can be obtained in polynomial-time. For unidirectional communication channels, which was proved to be NP-complete, we develop a set of lemmas which lead to a simple approximation algorithm whose theoretically guaranteed performance ratio is at most two.

Optimal placement of wavelength converters in trees, tree-connected rings, and tree of rings

In wavelength routed optical networks, wavelength converters can potentially reduce the requirement on the number of wavelengths. A recent study [Proceedings of 9th ACM-SIAM Symposium on Discrete Algorithms (1998)] raised the following problem: choose a minimum number of nodes in a WDM network to place wavelength converters so that any set of paths requires the same number of wavelengths as if wavelength converters were placed at all node. This problem is referred to as minimum sufficient set problem. It was shown to be NP-complete in general WDM networks [Proceedings of 9th ACM-SIAM Symposium on Discrete Algorithms (1998)], and be as hard as the well-known minimum vertex cover problem [Proceedings of 10th ACM-SIAM Symposium on Discrete Algorithms (1999)]. In this paper, we extend their study in trees, tree-connected rings, and tree of rings which are widely used topologies in the telecommunications industry. We show that the optimal wavelength converter placement problem in these two practical topologies are tractable. Efficient polynomial-time algorithms are presented.

Optimal wavelength converter placement in arbitrary topology wavelength-routed networks

This paper describes an algorithm for optimally placing a given number of wavelength converters in all-optical networks with arbitrary topologies. We first introduce the simple network model upon which the algorithm is based. We provide a formulation of the overall network blocking probability when a given number of nodes in the network, is provided with full wavelength conversion capability. We then present our optimal converter placement algorithm and illustrate its working using a simple example. The savings offered by our algorithm in the calculation of blocking performance are analyzed. The benefits of our optimal converter placement algorithm are studied through network examples such as the path, NSFnet and the mesh-torus. Finally, some heuristics for converter placement are presented.