The concept of an optical path layer has become increasingly attractive with the growth of traffic in the backbone network. The recent advances in optical switching technology support the deployment of optical cross-connect (OXC) nodes and the construction of large-scale optical path networks. This paper proposes a highly-reliable and fast pre-assigned restoration scheme for optical path networks. To achieve the pre-assigned restoration scheme, this paper investigates the extension of the Generalized Multi-Protocol Label Switching (GMPLS) protocol functionality considering the interoperability with GMPLS capable IP routers in the future. This paper also proposes a new network control architecture called the "partition model" through discussion of network architecture. We clarify that the M:N end-to-end restoration scheme achieves efficient resource usage and management of the network especially in the "partitioned model" network. With the finite design of the GMPLS protocol extension based on the M:N end-to-end restoration scheme, we successfully achieve an intelligent protocol that guarantees 100% recovery against single link failure and is capable of protection grade fast restoration of the optical path less than 50 msec. To our knowledge, this is the first demonstration of GMPLS-controlled protection grade fast optical path restoration.

We propose a simple configuration for colorless and directionless (CD) reconfigurable optical add/drop multiplexers that enables ultra-low contention add/drop operation to be achieved. In the configuration, we apply a combination of multiple small-port-count CD add/drop banks (CD banks) and round-robin CD bank assignment. Evaluation results show that the proposed configuration can substantially reduce intra-node contention rate, which is less than 0.1%. We also find that the proposed configuration can improve the utilization efficiency of wavelength resources and transponders. We discuss the mechanism of how the proposed configuration reduces intra-node contention by analyzing the status of wavelength assignments in direction ports and CD banks.

This paper describes the requirements for fault recovery on photonic networks and proposes a fast restoration scheme for recovering optical networks. The proposed scheme is a type of pre-assignment restoration. The features of the scheme are that it is suitable for multi-recovery classes aimed at fine control of the optical paths and that it establishes harmonization between restoration control and distributed network control such as in IP networks. The scheme is implemented on Photonic multi protocol label switching (MPLS) routers. A restoration demonstration was performed and recovery was achieved within 500ms in the optical layer.