IBM adds light to chips for terabit speeds

IBM has developed a manufacturing process that promises to accelerate the potential rate of data transfer between computer chips by using pulses of light, rather than electricity.

On Wednesday, IBM announced that its CMOS Integrated Silicon Nanophotonics technology integrates many of the electrical and optical communication devices needed for photonic communication onto the same piece of silicon and is consequently able to economically boost the speed and performance between chips.

"With optical communications embedded into the processor chips, the prospect of building power-efficient computer systems with performance at the exaflop level is one step closer to reality," IBM Research's vice president of science and technology TC Chen said in a statement.

Optical communications use photons instead of electrons to transmit data. A major limiting factor on the speed of optical communication is the rate at which data can be converted between light and electricity, which is itself limited by the power, complexity and size of the physical devices used for the translation. 

The technology will be able to eventually transmit data at a terabit per second, due in part to the new technique of fusing optical and electrical interconnects on the same piece of silicon, IBM research staff member Solomon Assefa told ZDNet UK on Wednesday.

"What is key here is for the first time we are integrating all of these things together and doing it in the CMOS framework," Assefa said.

CMOS — a complementary metal-oxide-semiconductor — is the prevalent technique for the manufacturing of digital chips, used by many manufacturing centres worldwide.

Chips using the technology can be made in existing semiconductor manufacturing foundries by "adding just a few more processing modules to a standard CMOS fabrication flow", IBM said.

The technology has the potential for a clear advantage over Intel's demonstrated 50Gbps silicon photonics technology, Assefa said.

"One major difference here is that Intel is basically making [its] CMOS chip and then making [its] nanophotonic chip on a separate piece of chip and then [it is] bonding them together. Here, we are integrating them on the same piece of silicon... if you are talking about exascale systems that are supposed to be 1,000 times faster than current supercomputers, you need integration," he said.

Intel has demonstrated an on-chip silicon laser light source, which Assefa said IBM currently lacks. "[Our] light source is an off-chip laser, operating at around 1.5 micron wavelength," he said. "In the near future, we have some plans for integrating the light source onto the chip, depending on the needs of our specific applications."

The development of the technology to make silicon communications possible on the same silicon as the processor is the culmination of 10 years' work by IBM research, IBM said. One key advancement was the Germanium avalanche photodetector, which was shown in March.

The initial goal of the technology is to build an exascale computer, Assefa said, but it could come to consumer hardware in time. "If you take a look at chips in Xbox and so forth, those are initially conceived for high-end applications and supercomputers, then they find their way into consumer technology." Assefa estimated it would take between 10 to 15 years for the technology to come to a consumer product.

The detailed results of the breakthrough were presented at the semiconductor industry conference Semicon in Tokyo on Wednesday, IBM said.