IBM stuffs 64Gbps of traffic down 'low quality' fibres

While there are politicians in Australia willing to argue that you can't predict the future capacity of fibre, IBM is doing just that, publishing an experiment that suggests the low-cost multimode fibres used for short-haul data centre links will support years of speed improvements.

What's interesting in this announcement isn't just the speed record (which probably won't last all that long anyway), but the demonstration that there's plenty of life left in fibres that are already in the field.

IBM used a vertical-cavity surface-emitting laser (VCSEL if you're thrifty with keystrokes) to pump 64 Gbps down a multimode fibre, for a distance of 57 metres. This, the company says, is more than 2.5 times as fast as current commercial-grade technology, and 14 per cent faster than the previous record for multimode transmission.

Since the high data rate was achieved using standard NRZ (non-return-to-zero) modulation, researcher Dan Kuchta of IBM's TJ Watson centre says today's technology “has at least one or two more generations of product life in it”.

Kuchta's team used VCSEL lasers from Chalmers University of Technology in Sweden as their transmitters, and silicon developed at TJ Watson to get high speed and sensitivity.

“The driver chip incorporates transmit equalization, which widens the bandwidth of the optical link. While this method has been widely used in electrical communication, it hasn't yet caught on in optical communication,” Kuchta said.

IBM says around 80 per cent of the fibre links used in data centres and supercomputer installations are less than 50 metres long, so they should be able to achieve the higher speeds its group demonstrated, once the technology is commercialised. ®

Bootnote: Fibre speed records have to be handled with care, because they're application specific. The flat-out-fastest laboratory demonstrations reach well into the petabit range; and speed records claimed for long-distance or metro links over single mode fibre are a different class of “record” to this demonstration. ®