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

Wavelength routed optical networks have emerged as a technology that can ef fectively utilize the enormous bandwidth of the optical fiber. Wavelength c onverters play an important role in enhancing the fiber utilization and red ucing the overall call blocking probability of the network. As the distorti on of the optical signal increases with the increase in the range of wavele ngth conversion in optical wavelength converters, limited range wavelength conversion assumes importance. Placement of wavelength converters is a NP c omplete 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 heuris tics for placing limited range wavelength converters in arbitrary mesh wave length routed optical networks. The objective is to achieve near optimal pl acement of limited range wavelength converters resulting in reduced blockin g probabilities and low distortion of the optical signal. The proposed heur istic is to place limited range wavelength converters at the most congested nodes, nodes which lie on the long lightpaths and nodes where conversion o f optical signals is significantly high. We observe that limited range conv erters at few nodes can provide almost the entire improvement in the blocki ng probability as the full range wavelength converters placed at all the no des. Congestion control in the network is brought about by dynamically adju sting the weights of the channels in the link thereby balancing the load an d reducing the average delay of the traffic in the entire network. Simulati ons have been carried out on a 12-node ring network, 14-node NSFNET, 19-nod e European Optical Network (EON), 28-node US long haul network, hypothetica l 30-node INET network and the results agree with the analysis. (C) 2001 El sevier Science B.V, All rights reserved.