Pushing fibre to its limits

According to Randy Giles, Executive Director and President of Bell Labs Seoul at Alcatel-Lucent, more planning is needed to ensure that fibre doesn't reach its limit, causing prices for capacity to increase dramatically.

Thanks to wavelength-division multiplex systems, capacity over fibre is now measured in tens of Terabits per second, and the cost to get data over that fibre has decreased while the demand for data increases exponentially every year. But Giles, who has been working with Bell Labs in optical research for 26 years, has warned that as we reach transfer rates measured in Petabits per second (1,000 Terabits), unless the methods of transporting data through the fibre change, the only way to increase capacity is to run additional fibre, and that comes at a cost.

"You want to have a cost containment as you're expanding this bandwidth," he said. "We're very concerned that we're getting to this threshold where doubling the bandwidth will only be done by doubling the amount of fibres deployed and equipment deployed, resulting in nothing but a linear increase in price, and that's very hard on the end users.

"If we had the same price schedules on the bits delivered today as we had 10 years ago, we wouldn't be able to afford watching videos."

Bell Labs is currently researching ways to get the most out of fibre, through having multi-mode fibre where there can be multiple transmissions, and through re-engineering the fibre so that instead of just having a single core that carries all of the wavelength multiplex channels, there can be several cores in the single strand of glass.

Giles said that Bell Labs is testing three-core and seven-core strand of glass fibre, but he said it would be a while before it would get out of the lab.

"It's a few years out to call this a practical solution...because for each of these challenging aspects to the implementation of multimode or multi-core, there have been several technology solutions," he said. "When you have the complement of several technology solutions, it does take time to evolve the selection of what may turn out to be the best one.

"People don't have a full understanding of the cost of manufacture versus the cost of getting one of or a few components to demonstrate the method."

Despite its potential future limitations, fibre is still performing much better than legacy copper, and Giles noted that copper is being replaced everywhere.

"Even with copper, if we're talking about very high capacity, even chip-to-chip communications are more and more using optics rather than copper," he said, but added that copper might make a comeback.

"It's one of these things people say: If you're competing against silicon, give up. In some sense, if you're competing against copper, you should really be cautious to claim victory against copper, because copper continues to surprise in many of the solutions people have found."