Optical transport network design with collocated regeneration and differential delay compensation

A potentially cost-effective approach for augmenting the transmission capacity in an optical transport network (OTN) consists of bundling several optical channels by means of an inverse-multiplexing strategy, e.g. virtual concatenation (VCAT). When VCAT is employed together with multipath routing, the differential delay between concatenated channels needs to be compensated via electrical buffering. To avoid installing large and costly high-speed buffers, this compensation can be dispersed throughout the intermediate path nodes. With this distributed scheme, each intermediate compensation operation requires an optical-electrical-optical (OEO) converter. Such converters, which are typically employed to allow electrical processing (e.g. signal regeneration, traffic switching/grooming, etc.), represent the largest contributor to the capital expenditures of an optical network. Hence, to save on OEO equipment and keep the network cost-effectiveness, we propose the novel approach of collocating the differential delay buffering and the regeneration on the same network element, enabling the implementation of distributed schemes with minimal link capacity levels, OEO count, and buffer size requirements. To effectively design an OTN network under these conditions, we also present a new multi-step optimization framework based on integer linear programming (ILP) modeling. To test our approach, emerging 100 Gb/s Ethernet services are established over two reference networks using virtually-concatenated 40 Gb/s channels. The correspondent results confirm that relevant OEO/regenerator count savings (ranging from 23% to 44%) can be attained with the collocated approach while the buffer sizes are maintained reasonably small. We also show that the end-to-end transmission latency is not affected by the adoption of this collocated strategy