Source: Wired

A new research breakthrough from Intel combines silicon chips and lasers to transmit data at 50 gigabits per second — and someday, maybe as fast as a terabit per second.

The 50-Gbps speed is enough to download an HD movie from iTunes, or up to 100 hours of digital music, in less than a second.

The technology, known as silicon photonics, can be used as a replacement for copper wires to connect components within computers, or between computers in data centers.

“The fundamental issue is that electronic signaling relying on copper wires is reaching its physical limits,” says Justin Rattner, chief technology officer for Intel, which announced the breakthrough Tuesday. “Photonics gives us the ability to move vast quantities of data across the room or planet at extremely high speeds and in a cost-effective manner.”

Photonics refers to the generation, modulation, switching and transmission of light, and can be done using lasers or light-emitting diodes.

Over the next two years, Intel hopes to perfect the technology by improving the efficiency of the lasers, as well as the packaging and assembly of the silicon chips and the manufacturing techniques needed to churn out millions of these modules.

“We have a good sense of the challenges here and what it takes to put all the components together, so we expect the technology to be widely deployed by the middle of the decade,” says Mario Paniccia, director of the Photonics technology lab at Intel.

Copper cables are the lifeblood of computing today. But they are limited by length because of the signal degradation that comes with using them over distances.

“At speeds of 10 Gbps and higher, it is difficult to move electrons fast enough and with enough signal strength to beat the tradeoffs,” says Rattner.

This limits the design of computers, forcing processors, memory and other components to be placed just inches from each other, says Intel. The alternative is to transmit data over optical fiber, but that is expensive and also limited.

“It’s not an issue if you are using only a few of them in an undersea cable,” says Rattner, speaking about optical fiber cables. “But if you want to have optics widespread, from consumers to supercomputers, the cost has to be taken down or it is not practical.”

That’s where integrated silicon photonics could come in. Using silicon-based chips and the same manufacturing process currently used for those chips, photonics modules could replace copper connections.

It could change how computers and data centers are designed in the future, says Intel. Earlier this year, the company showed its Light Peak technology that uses optics to deliver bandwidth of 10 Gbps and higher. Silicon-based photonics can go much higher, reaching tera-scale data rates, says Intel.

Here’s how the silicon photonics prototype works to achieve the 50-Gbps rate. Each module has a silicon transmitter and a receiver chip. The transmitter chip has four lasers whose light beams travel into an optical modulator. The modulator encodes data onto them at 12.5 Gbps. The four beams are then combined to output a total data rate of 50 Gbps.

The receiver chip at the other end of the link separates the four optical beams and directs them into photo detectors. The detectors convert the data back into electrical signals.

“In the labs, we ran this for 27 hours with no errors and transferred about a petabit of data,” says Paniccia. “And all this at room temperature with no fancy cooling.”

The silicon-based photonics chip could be used within a computer or to communicate from server to server in a data center. “If we are talking about CPU-to-memory connection, we would take our photonics chip and put it close to the CPU to bypass the copper interconnects,” says Paniccia. “For now we are not talking about integrating with the CPU.”

As the next step, Intel researchers are trying to increase the data rate by boosting the modulator speed and increasing the number of lasers per chip.

“If you increase the data rate of the modulator and put more than four lasers on a chip you can scale the whole thing,” says Paniccia. “The 50-Gbps rate is just the beginning.”