Researchers speed up data rate down optical fibre link
European researchers have developed technology that increases the speed of data transmission over fibre optic broadband connections into homes and offices. As part of the EU-funded Muse project, the aim of which is to offer broadband to all European citizens, the team of researchers from Siemens Network achieved downstream transmission rates of 10Gbits per second and upstream speeds of 2.5Gbits per second over a Gigabit Passive Optical Access Network (GPON). This is four times faster than current GPON technology, which reaches downstream data rates of 2.5 Gbit/s and upstream rates of 1.2 Gbit/s. 'Faced with the demand for increased bandwidth, the market for optical networks has experienced a huge upswing in recent years,' explains Christian Unterberger, President Fixed Networks at Siemens Networks. 'This is now boosting research and development as well. We are very confident that we can further develop systems of the next PON generation to reach final market readiness by the year 2009,' he added. The researchers implemented an optical amplifier, a so-called erbium-doped fibre amplifier (EDFA). Optical fibres doped with the element erbium amplify the optical signal of the system and enable longer transmission ranges with higher bandwidth. This device was developed in such a way that a purely optical bi-directional amplification is possible. The result is one single compact device that can boost optical signals both from the end-customer to the exchange and from the exchange to the subscriber. In addition, the researchers were also able to extend the distance between the hub and subscribers from 20 to 100 kilometres. The number of subscriber lines per splitter, where the optical signal is divided up to serve more destinations, was also expanded from 64 to 512. The new system is expected to provide at each hub greater bandwidth, as well as to offer cost-efficient lines to subscribers in more sparsely populated areas. In addition, the higher split factor in urban areas will allow more subscribers to be connected to a system. At the same time, the PON system will eliminate the need for the aggregation devices that are commonly used to collect and distribute data traffic locally. In the future, it will be possible to connect subscribers directly to the core network. According to Siemens, many operators are keen to deploy high speed broadband access systems that offer greater speed than DSL technology, which uses existing copper twisted pairs to provide data rates of up to 50Mbit/s. Services such as Video on Demand (VOD), Voice over Internet Protocol (VoIP) and High Definition Television (HDTV) are expected to perform much better when delivered over fibre-optic subscriber lines. In addition to Siemens, the Universities of Eindhoven and Essex, the Heinrich-Hertz-Institut Berlin of the Fraunhofer Gesellschaft and leading European network operators are participating in the MUSE project.