Virtual ring based protection for Time-Domain Wavelength Interleaved Network

We propose a protection scheme for Time-Domain Wavelength Interleaved Network (TWIN), an optical burst switching technology for transport networks, where each destination node uses a dedicated wavelength, while sources are equipped with fast tunable lasers. TWIN is composed from several multipoint-to-point trees built on top of a mesh network linking sources and destinations. Each multipoint-to-point tree in TWIN has its root in a destination node, and is thus used for the reception at a single, unique wavelength. In the proposed method resource allocation is centrally performed in order to avoid contention on the multipoint-to-point trees while optimizing source activity. We propose using a virtual ring joining all sources and destinations in order to support both an out-of-band control channel and all protection paths. The control channel may be used in particular to carry messages related to network discovery, synchronization and protection issues. Synchronization and failure notifications (generated by standard optical layer monitoring procedures) are processed by the central element in charge of resource allocation. The proposed TWIN layer protection approach avoids using lower layer protection techniques, which may strongly impact the fiber length distribution, and thus the associated scheduling mechanism, inside the different multipoint-to-point trees. The use of a single virtual control ring is well suited to networks with a limited extension such as metro networks. Our approach can however be extended to larger scale networks by using several control rings. We describe an algorithm to cover a large network operated by TWIN with minimum number of interconnected rings, taking into account the maximum transparent reach for protection paths.