CORDIS Archive

Photonics - Tripping along the Light Fantastic

There are currently two ways which increase the amount of data that a fibre can carry. The first involves using more than one colour (i.e. wavelength) as a carrier for the signal. This is called Wave Division Multiplexing (WDM) and currently four wavelengths are common and sixteen have been achieved. The second is a much more curious phenomenon called the soliton.

A soliton is a shaped pulse which is able to travel long distances through the glass of an optical fibre with minimal degradation to its shape. This is because of a balancing act amongst the factors in the fibre that affect the light. Even stranger is that the soliton, despite its sci-fi name, is not a recent discovery and is not limited to light. The phenomenon was in fact first observed in a wave on water in 1834 and was the subject of ACTS projects ESTHER, MIDAS and UPGRADE.

A further technique, giving an increase in speeds by improving the electrical modulation, has been demonstrated by projects SPEED and HIGHWAY.

It is already possible, by using these techniques, to increase fibre capacities so that millions of people - the population of Austria being the oft-quoted example - could hold simultaneous telephone conversations down a single fibre.

The operation of an all-optical network has been demonstrated by projects OPEN, METON, PHOTON, WOTAN, MOON and others. SONATA is working on an all-optical distributed switching network, and CAPITAL, BLISS, FAST, ACTUAL, VERTICAL and PHOTOS have been developing new photonic components for amplification, distribution and switching.

But how is this going to benefit the home consumer in Europe? The current investment in copper is so great that it is much more cost-effective to consider a hybrid approach to broadband networks. The length of a local loop of copper - the twisted pair that runs from the subscriber to the telco's distribution cabinet in the street - is of the order of 1000 metres in Europe on average. This means that a photonic network can be envisaged which links to a final stretch of copper for the final run to the home. The signal would be carried using ADSL, VDSL or similar technologies which allow megabit data rates to be carried down a consumer’s telephone line at the same time as conventional telephone signals. This is the essence of a hybrid opto-electronic distribution system. (Projects BROADBANDLOOP, TOBASCO, PRISMA, FRANS, PLANET and COBNET have worked on this.) End users would still have accesss to tens of megabits of data - enough for television, Internet and more - whilst the potential bottlenecks of the trunks would use ever-faster photonic systems.

The work done in ACTS (as in RACE before it) is facilitating Photonics as a key area in the development and deployment of new systems for the Information Society.

By Andy Finney,Independent Multimedia Co., 20.12.99