Optical packet routing using orthogonal labelling – results from the FP5 STOLAS project

FSK/IM orthogonal labelling of data packets enables high router throughputs and hybrid circuit-/packetswitched networks. The node cascadability is limited by the required payload extinction ratio, and the speed of the label swapping wavelength converters. Introduction Today’s networks show an ever-continuing growth of packet-based data traffic, driven by heavy internet usage, peer-to-peer traffic, on-line gaming, etc. The throughput of a packet-routing node can be increased significantly by switching the payload data transparently without opto-electrical-optical conversion. In order to control this routing, each packet carries a label that can be split off easily and processed separately. Various ways have been reported to embed the label information in the data packets [1]: on a subcarrier outside the payload spectrum, in an other wavelength channel running parallel to the data channel, serially in front of the payload data, or by using optical code division multiplexing for encrypting the label on the payload data. These ways each have their pros and cons, by e.g. requiring extra spectrum for the label, strict synchronization between payload and label, increasing sizeably the line rate, etc. In the EU FP5 project STOLAS, which has been concluded recently, an alternative labeling approach has been pursued, the so-called ‘orthogonal labeling’, which uses two basically independent modulation dimensions for the payload and the label [2]. This paper discusses the implementation of this approach, its networking aspects, some experimental results, and a first application example in hybrid circuit/packet-switched networks.