In this paper, a cycle-based network recovery method for optical mesh networks is studied. The study in this paper concentrates on improving two performance requirements on network recovery: efficient spare resource utilization, and robustness for multiple failures. The proposed method uses multiple ring-covers and performs distributed link restoration using preplanned logical cycles embedded in physical mesh topologies. This method provides fast and simple recovery operation by exploiting the characteristics of ring topology and also provides efficient resource utilization by using multiple backup paths per link to improve the sharability of overall spare resources in the networks. With this method, layered reliability can be provided to network services by enabling priority-based robustness against multiple failures. The performance results reveal the trade-off between the resource efficiency for single failure and the robustness for multiple failures, and show the preconfiguration of a few logical cycles per link can provide enhanced resource efficiency and priority-based hierarchical robustness.

In this paper, a semi-dynamic protection path configuration method is proposed for WDM optical networks. In the method, the protection path is established by connecting several sub-lightpaths from the source node to the destination node of the original working lightpath, as opposed to conventional path restoration method where a single protection lightpath between the source-destination pair performs restoration. The proposed method provides enhanced flexibility in protection path configuration and relieves the cost of spare capacity reservation. This paper also studies the effects of wavelength conversion capability of intermediate optical cross-connect nodes on protection path routing and spare capacity utilization. In terms of spare capacity utilization, the proposed method shows substantial reduction of spare capacity overhead compared with dedicated path restoration in all optical networks without wavelength conversion, and shows similar capacity efficiency compared with shared path restoration in opaque networks with full wavelength conversion capability. In terms of robustness, the proposed method shows nearly the same restoration ratio for double-link failure as that of dynamic restoration method.