A Graph Technique to Determine the Minimum Number of Wavelength for some WDM Optical Networks

Abstract

Wavelength division multiplexing (WDM) is a promising technique to utilize the enormous bandwidth of the optical fibre (~50 terabits per second) into multiple communication channels with bandwidths (~10 gigabits per second) compatible with the electronic speed of the end users. In WDM network, it is possible to route data to their respective destinations based on their wavelengths. The use of wavelength to route data is referred to as wavelength routing and a network which employs this technique is known as a wavelength routed network. When network does not employ any intermediate O/E conversion between access stations, it is called as an all-optical wavelength routed network. In order to send data from one access station to another station, one needs to establish a connection in the optical layer similar to the case in a circuit-switched network. This can be realized by determining a path in the network between the two nodes and allocating a free wavelength on all of the links on the path. Such an all optical path is referred to as a light path and may span multiple fiber links without any intermediate electronic processing. The entire bandwidth available on this light path is allocated to the connection during its holding time during which the corresponding wavelength cannot be allocated to any other connection. This requirement is referred to as wavelength continuity constraint.