Resource utilisation analysis in WDM backbone networks

Circuit-switched backbone networks are appealing especially due to their low switching cost. However, some of their links may be poorly utilised with respect to the available capacity. Grooming can be used to improve this utilisation: optically switched lightpaths are groomed in fibres using WDM, and flows are groomed in lightpaths using TDM. However, grooming require more transmission resources if lightpaths/flows are not following the shortest-path and take detours. It can thus be counterproductive. In this paper, we propose an approach detailing the resource utilisation at two levels: lightpaths and fibres. Assuming a practical network layout, our approach measures the impact of the fibre and lightpath granularities and of the wavelength continuity constraint on the link utilisation. It also analyses to which extent detours consume resources. We apply this resource utilisation analysis to a set of layouts provided by a heuristic. Numerical results show how our approach can be used to further improve a layout or a heuristic.