Profit Maximization in Flex-Grid All-Optical Networks

All-optical networks have been largely investigated due to their high data transmission rates. The key to the high speeds in alloptical networks is to maintain the signal in optical form, to avoid the overhead of conversion to and from electrical form at the intermediate nodes. In the traditional WDM technology the spectrum of light that can be transmitted through the optical fiber has been divided into frequency intervals of fixed width with a gap of unused frequencies between them. In this context the term wavelength refers to each of these predefined frequency intervals. An alternative architecture emerging in very recent studies is to move towards a flexible model in which the usable frequency intervals are of variable width. Every lightpath is assigned a frequency interval which remains fixed through all the links it traverses. Two different lightpaths using the same link have to be assigned disjoint sub-spectra. This technology is termed flex-grid or flex-spectrum. The introduction of this technology requires the generalization of many optimization problems that have been studied for the fixed-grid technology. Moreover it implies new problems that are irrelevant or trivial in the current technology. In this work we focus on bandwidth utilization in path toplogy and consider two wavelength assignment, or in graph theoretic terms coloring, problems where the goal is to maximize the total profit. We obtain bandwidth maximization as a special case.