Design of p-Cycles under a Wavelength Continuity Assumption

While there are many studies on the efficient design of p-cycles which advertise their spare capacity efficiency, few of them consider such a design under the wavelength continuity assumption, i.e., no wavelength converter at any node. In this paper, we propose to investigate thoroughly the issue of wavelength conversion vs. wavelength continuity for p-cycles, with large scale optimization tools in order to get an exact estimate of the consequences of the wavelength continuity assumption on the spare capacity requirements and on the provisioning cost. Differences with previous work are that we consider exact efficient scalable models instead of heuristics, as well as joint optimization of routing and protection schemes. In addition, with respect to the on-line generation of p-cycles, we allow the simultaneous generation of several node disjoint cycles without hindering a proper consideration of straddling links, leading to a significantly improved scalability. Numerical results show that, although the capacity requirement under the wavelength capacity is higher than under a wavelength continuity assumption, the difference is not significant. Therefore, due to the reduced provisioning cost (saving at least on the converters), designing p-cycles under a wavelength continuity assumption is clearly advantageous.