We propose a new design scheme of resilient Wavelength Division Multiplexing (WDM) networks by extending and reshaping pre-configured protection tree (p-tree) structures. The resulting protection scheme relies on optimized pre-cross connected structures that span all previously proposed protection patterns.

p-Tree-based protection schemes offer the advantages of scalability, local restoration capabilities, and failure impact restriction, but at the same time suffers from capacity inefficiency. While keeping these advantages, we propose an extension (reshaping) of the p-tree protection pattern that imposes no restriction on the shapes of the protection building blocks. Not only the resulting protection scheme remains scalable and highly flexible, but it also leads to pre-configured protection structures that improve much further on capacity efficiency and recovery delay.

We establish some new integer linear programming models, and use large scale optimization tools, namely column generation (CG) to solve them. Our CG-based solution method is highly scalable as it does not require an a priori explicit enumeration of the protection structures, but an efficient dynamic enumeration of only the most promising ones. Comparison are made with three other protection schemes, i.e, simple and non-simple p-cycles (fully pre-cross connected structures) as well as p-trees. Results show a clear advantage of the proposed extended-tree scheme with respect to flexibility, capacity efficiency, and restoration delay.