An article at Computerworld explores whether the limitations of traditional interconnects will soon make the Moore’s Law debate (it’s dead, it’s not dead) irrelevant. Author Lamont Wood, argues that the interconnect bottleneck poses the greatest threat to performance improvements. Moving data optically, via silicon photonics, may provide a way of resolving the data traffic jam.
The article cites Linley Gwennap, principal analyst at The Linley Group, who believes that processors will come up aginst a performance wall in as little as five to ten years. It won’t matter how fast they are if the data flow is restricted.
There are range and speed limitations associated with copper interconnects. According to Marek Tlalka, marketing vice president at photonics vendor Luxtera Inc., at 40 gigabits per second bandwidth, copper’s current top-speed, the signal falls to inches. Another expert at market research firm In-Stat questions whether transmission rates for copper will ever get to 100 gigabits per second.
With silcon photonics, data moves through paths constructed of laser light beams. The data paths can cross each other without interference and different signals can even share the same path as long as they use different wavelengths (i.e., colors). Silicon photonics is also extremely energy-efficient and can transfer data over longer distances, about 10 kilometers (around 6 miles).
Until recently, optical componentry was quite expensive, often prohibitively so, but manufacturing advances have brought costs down. Also, by their nature photonics structures are large relative to electrical components, but there is still room to pack the components tighter than is done with photonics currently, explains Luxtera’s Tlalka. Another work-around to the size problem is to use external lasers, as Luxtera does, instead of building a source of laser light directly onto the chip.
Intel is a big proponent of optical technology and so is Intel Labs Director Justin Rattner: “We felt that over the long term we have got to be moving data optically. Conventional electrical cables have too many physical limitations, while fiber has basically no limitations,” he states.
Rattner sees a near future where customers will be given a choice between an electrical or an optical interface and believes a terabit of bandwidth will be achieved by the end of the decade.