Intel light-beam technology moves data at 50Gbps

This is the equivalent of transmitting an entire HD movie in a second.

The chipmaker claims its prototype silicon-based optical data connection with integrated lasers is a world first and further advances the quest to use light beams instead of electrons to carry data in and around computers.

Currently, computer components are connected to each other using copper cables or traces on circuit boards. Due to the signal degradation that comes with using metals such as copper to transmit data, these cables have a limited maximum length. This limits the design of computers, forcing processors, memory and other components to be placed just inches from each other.

Intel says its research achievement is another step toward replacing these connections with extremely thin and light optical fibres that can transfer much more data over far longer distances, radically changing the way computers of the future are designed and altering the way the data centres are designed.

While telecommunications and other applications already use lasers to transmit information, current technologies are too expensive and bulky to be used for PC applications.

Intel’s 50Gbps technology, dubbed the Silicon Photonics Link, combines previous breakthroughs, including the first Hybrid Silicon Laser co-developed with the University of California at Santa Barbara in 2006, as well as high-speed optical modulators and photodetectors announced in 2007.

The hybrid silicon laser combines the light-emitting properties of indium phosphide with the light-routing capabilities of silicon into a single hybrid chip. When voltage is applied, light generated in the indium phosphide enters the silicon waveguide to create a continuous laser beam that can be used to drive other silicon photonic devices.

Intel’s transmitter chip is composed of four such lasers, whose light beams each travel into an optical modulator that encodes data onto them at 12.5Gbps. The four beams are then combined and output to a single optical fibre for a total data rate of 50Gbps. At the other end of the link, the receiver chip separates the four optical beams and directs them into photo detectors, which convert data back into electrical signals.

The company claims that both chips are assembled using low-cost manufacturing techniques familiar to the semiconductor industry.

Graham T Reed, head of the Silicon Photonics Research Group at Surrey University, was present for the Intel announcement in Santa Clara, California and said it was an important step towards a commercial product.

‘This was also the first time they have integrated lasers into an optical link,’ he said. ‘They showed four independent channels working at four wavelengths, each driven via a different hybrid laser.

‘The significance for computing is that the interconnect that was seen to be a future bottleneck in the communications link for computers, can now be optical, and therefore can have huge bandwidth.

‘Optical connections have already demonstrated that they are the best way to make long connections, for example international fibre optic links, and now this announcement challenges people to make the shorter connections optical as well.’

Reed added, ‘It means faster and better communications within computing, but the benefits could also be felt in other areas as this technology is applied in other places. For example, optical connections to individual homes or businesses will mean much more information can be provided, perhaps via the internet, in a much shorter time.’

Intel researchers are currently working to increase the data rate by scaling the modulator speed, as well as increase the number of lasers per chip. This may mean that, one day, the optical link would be capable of transmitting data at terabit rates, which is fast enough to transfer a copy of the entire contents of a typical laptop in one second.

Opto-electronics expert Alwyn Seeds, head of UCL’s department of electronic and electrical engineering, said the latest achievement from Intel is ‘remarkable’, but there is still much work to be done before the technology is ready for widespread computing applications.

‘The integration process has to be developed to be fully compatible with silicon active device processing,’ he told The Engineer.

Seeds added that the technology also needs to demonstrate that it will have long-term reliable operation over normal integrated circuit temperatures and power consumption must be made low enough to not constrain chip architecture.

‘There are a number of competing integration technologies, including even direct epitaxial growth of compound semiconductors on silicon, that may yet deliver higher manufacturing yield,’ he said. ‘None of this, however, should detract in any way from the remarkable achievements announced by Intel and University of California at Santa Barbara.’

Reed said optical computing is going to become more important as personal, business, medical, social and scientifc sectors need to move increasing amounts of data more quickly.

‘It’s early days yet, but the impact, not just of this announcement, but of silicon photonics in general could be massive,’ he said. ‘It’s a very exciting time to be working on it.’