Do we need yet another local area network? If it runs at 40Gbps and we’re building a multimedia intranet, perhaps we do. At all events, researchers at British Telecommunications Plc’s BT Laboratories on Martlesham Heath in Suffolk, UK have been showing off their latest miracle, a prototype of a fiber optic local network called SynchroLan. Designed to connect high-end computers, it uses a bus rather than a ring topology, and each computer – at present the thing can have up to 16 nodes – is allocated a time slot during which it can transmit data on the bus, and British Telecom calls the technology optical time division multiple access. At the other end, the receiving computer synchronises with the appropriate time slot, a process that takes 100nS. The company bills it as a simpler alternative to crossbar switching because its complexity scales linearly with the number of ports rather than according to square law, transmission is combined with switching, and broadcasting as well as point-to-point transmission are inherent in the use of a local net. The company also sees it scaling up to 100Gbps with current technology and 1Tbps with all-optical switching. In the current version, a single 2.5GHz train of optical pulses acts as the clock for the entire network, setting the maximum speed for each node at 2.5Gbps. An entire node – which can support a workstation, a slow speed local network or a gateway to a wide area network, currently fits a 19 rack but could be shrunk to fit a board. As to the maximum distance between nodes and end-to- end, when we might see the thing launched as a product, and how much it is likely to cost, per node or overall, those are among the questions for another day as nobody was available at Telecom to talk about the thing yesterday.