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Intel announced today that it has reached a milestone in its efforts to replace copper wiring with light by creating a stable, 50Gbps link between two devices using fiber optics. Dubbed "silicon photonics," the chipmaker's innovations are the basis for a fiber optic interconnect that can be theoretically scaled to 1Tbps for device-to-device and wide-area networking connections. Those same innovations could one day be used to replace copper interconnects in electronic systems.
One of the key innovations that drives this technology is research conducted in concert with UC Santa Barbara to develop hybrid silicon lasers. Using a unique process to bond indium phosphide to silicon along with carefully etched gratings in formed silicon waveguides, designers are able to create variable-wavelength solid state laser emitters by merely manipulating the etching pattern.
The light generated from these tiny lasers can be guided along etched channels called waveguides, and modulated with tiny silicon modulators that have ramped from a few hundred megahertz at the beginning of the millennium up to the current versions which can work at frequencies high enough to transmit 40Gbps on a single channel. Separate channels are muxed together and sent along a single fiber optic cable. On the receiving end, the composite light is demuxed into separate wavelengths, and each one is fed into a separate photodetectors for decoding.
The entire transmit and receive modules are single chips with special aligning pins to connect the fiber at each end. The current implementation uses four hybrid silicon lasers at different wavelengths, each encoded at 12.5Gbps, for a total of 50Gbps throughput. In the lab, the link was tested continuously for 27 hours, transferring over a petabyte of data with nary an error. Intel says this translates into a bit-error-rate less than 3e−15.
The bandwidth can be scaled by increasing the number of lasers operating at distinct wavelengths, or by increasing the encoding speed. By bumping the number of channels to 25 and the encoding rate to 40Gbps, speeds of 1Tbps are possible. Intel believes this could be pushed even further, but to give you an idea of what kind of data you can shuffle around at these speeds, consider this: at 50Gbps, in less than one second you could transfer an entire HD feature length film; at 1Tbps, you could move as many as three whole seasons of Law & Order. At that speed, you could download the entire printed collection of the Library of Congress in under two minutes.
The company plans to ramp up the tech for volume production, and expects to have it "widely deployed" by 2015. "We've demonstrated that in principle that we have all the pieces," said Dr Mario Paniccia, Intel Fellow and director of the company's Photonics Technology Lab, during a press conference this afternoon. "We need to develop a high-volume manufacturing process, and optimize power, packaging, and assembly. The process technology is CMOS-like, which is within our core competency. Our biggest challenge is testing its reliability, but we don't foresee any fundamental issues."
"This is the future path for increasing bandwidth," he added.
Intel CTO and director of labs Justin Rattner said the company isn't just eyeing high-end interconnect applications, either. "Current tech is about $100 per port; we're looking to take this down to $1 per port."
We asked how Intel's silicon photonics tech relates to its upcoming LightPeak standard. "Current LightPeak uses discrete optical components, and that's currently a 10Gbps tech," Rattner told Ars. "Scaling that up to higher speeds is going to be very challenging. Using multiple VCSELs would drive cost up. The second or third generation of LightPeak would be an excellent candidate for silicon photonics."
While silicon photonics is currently being used for device-to-device connections, the technology could be used to move data from one chip to another inside a PC or mobile device, for instance. "The real benefit will be realized when we begin to integrate photonic devices together, which can enable things that weren't possible or practical before," Rattner said.
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