Performance analysis of the effect of shorter lightpaths on the design of wavelength-routed WDM optical networks

Finding the optimum path for each source-destination pair and assigning a wavelength to that path from the available wavelengths in optical networks, implemented using wavelength division multiplexing techniques, is termed as wavelength routing. In this work, we extend the usual concept of shortest path (SP) to shorter paths (also known as alternate paths) for computing optimal routes for lightpaths. A connection request may not be blocked if a wavelength is available on a shorter (hence costlier) path from source to destination but not on the shortest path. The objective is to minimise the number of blocked paths (without much increasing cost) by considering the alternate paths between source-destination pair. Extensive performance study, which includes the number of blocked paths (i.e., blocking probability), cost and execution time, has been conducted for each routing strategy in different networks under varying number of wavelengths. The results indicate that there is an upper bound on the number of alternate paths to be considered in wavelength-routing, beyond which the successful number of traffic assignments does not improve considerably even with increase in alternatives