Intel: Silicon photonics to replace copper
Intel's 50-Gb/s silicon photonics transmit module: Laser light from the silicon chip at the center of the green board travels to the receiver module, upper right, where a second silicon chip detects data on the laser and coverts it back into an electrical signal.
Silicon photonics will replace copper connections in everything from supercomputers to servers to PCs, according to Intel Corp. researchers who demonstrated 50-Gb/s optical transmitter and receiver chips that it plans to scale up to terabit-per-second speeds prior to commercialization.
"This milestone marks the beginning of silicon photonics in the high-volume marketplace, in applications from [high-performance computing] all the way down to the client" PC, said Mario Paniccia, director of Intel's Photonics Technology Lab. "We call it a concept vehicle, but we've done the key things that would need to be addressed to commercialize it," added Paniccia. "We see a clear development path from 50 Gbits per second today to a terabit in the future."
Optical connections can operate over longer distances than copper wires, according to Intel, and could eventually replace not only the copper connections between systems, but those between boards in the same system and eventually between cores on the same board. The chip maker already has a 10-Gbit/s Light Peak chip that uses conventional optical technologies. Intel's Photonics Technology Lab is leveraging its silicon manufacturing expertise to build photonic components. Paniccia estimated that the first commercial applications of silicon photonics will begin appearing in as little as five years in data centers and supercomputer facilities.
Intel's concept vehicle is based on technologies developed since 2004. The modulators required to encode optical information using signal waveguides and photodiodes were cast in silicon on custom chips designed by Intel. The transmitter chip uses Intel's hybrid silicon laser technology that bonds a small indium phosphide die to on-chip silicon waveguides. It is then patterned into a connected optical laser, four of which were placed on the transmitter chip.
"We combined our silicon manufacturing techniques with our hybrid laser, and demonstrated an integrated transmitter using four lasers each operating at a different wavelengths and four silicon modulators each operating at 12.5 Gbits per second, then combined them together into an aggregate 50 Gbits per second into the optical fiber," said Paniccia.
The optical fiber output on the receiver chip was filtered into separate colors, then diverted by waveguides into four separate photodiodes, each of which recovered one of the four separate 12.5-Gbit per second channels.
Next, Intel plans to add more lasers per chip, increase the number of channels and focus on optimization, power reduction and improved efficiency. It then hopes to commercialize the optical connection technology.
- R. Colin Johnson
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