Circuit switching in multi-hop lightwave networks

Abstract

Emerging high speed networks are using optical fibers employing time division synchronous communication. In these systems the use of optical switching is strongly advocated due to the bottleneck created by store and forward in electronic components. Switching solutions geared toward optical systems have been proposed so far only for packet switching networks. This paper introduces a new circuit switching approach for the emerging time division controlled fiber optic networks based on the requirement to avoid store and forward at intermediate nodes. The approach, termed Fast Circuit Switching (FCS), is unique in several operational and performance aspects. In terms of the way time slots within each cycle are allocated, a circuit is guaranteed a transmission slot immediately upon arrival at every intermediate node. As a result, the proposed Fast Circuit Switching (FCS) can be implemented by pure optical switches. In terms of performance, FCS guarantees minimum data transmission delays, consisting only of the end to end propagation delay in the network. Lastly due to being based on fixed time allocation at intermediate nodes, the FCS controlled system is purely end to end controlled. These properties make FCS inherently suitable for efficiently implementing circuit switching in wide area fiber optic networks, particularly, for supporting real time communications. The realization of slot assignments, which support the FCS solution, entails a novel graph oriented algorithmic approach. Several new algorithms for allocating circuits according to FCS are presented, dealing with fixed, as well as dynamic, circuit management. It is shown that, while providing unique operational and performance advantages as discussed above, the FCS is also bandwidth efficient, requiring only system bandwidth similar to conventional circuit switching methodologies.