Comparative study of fully pre-cross-connected protection architectures for transparent optical networks

Protection architectures that have the property of pre-cross-connection are advantageous to the implementation of transparent optical paths. A pre-cross-connected protection path can be in a known-good working condition before use, whereas on-the-fly assembly of a protection path through transparent concatenation of optical channels may not rapidly satisfy the optical path integrity objective. In this study, several pre-cross-connected architectures were compared on the basis of spare capacity cost for 100% single failure restorability, the dual failure restorability of these designs, and the ability of each architecture to support a feasible wavelength assignment and limits on the maximum length of transparent optical paths. The architectures considered were p-cycles, failure independent path-protecting (FIPP) p-cycles, demand-wise shared protection (DSP), pre-cross-connected trails (PXTs), span-protecting p-trees, and path-protecting p-trees. The results give insight into the relative merits and demerits of these architectures.