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Intel claims quantum leap in fiber-optic detectors

The chipmaker has developed silicon-based photoelectric detectors that could cut the cost of fiber-optic communications to a fraction of their current value.
Written by Alex Serpo, Contributor
Intel has developed silicon-based photoelectric detectors that could cut the cost of fiber-optic communications to a fraction of their current value.

Photodetectors — used in a range of applications, such as fiber-optic communications, image sensors, datacenter interconnects and optical drives — have been significantly more expensive than a copper-based equivalent.

According to Mario Paniccia, Intel fellow and director of Intel's photonics lab, this is due to the high cost of rare transition metals used in the optical devices.

"[Photonics] is today a technology predominately made with what we call exotic materials — indium phosphide, gallium arsenide, lithium molybdate — which involves expensive processing, very low volumes and, more importantly, very complex packaging and hand assembly," Paniccia said.

However, Intel claims to have found a way to create photodetectors using cheap silicon doped with a small layer of the element germanium, drastically reducing cost.

"Just to put it into context, a commercial [photodetector] that is used in telecoms typically sells for $200 to $300," Paniccia said. "We're talking devices that are probably an order or two in magnitude lower in cost." This prediction makes Intel's devices between 10 and 100 times cheaper than current photodetectors.

This lower cost opens up many applications, including making fiber to the home a great deal more accessible for consumers. The chief operating officer of Australian telecoms firm Tesltra, Greg Winn, recently explained this to ZDNet sister site ZDNet.com.au.

"If you run fiber, you need a device that breaks it down to the inside wiring, to the copper, and those devices are maybe a few hundred dollars," Winn said. "We do that today, but it's not economic to do it unless you're guaranteed the uptake of the services that the fiber requires."

In addition to lowering cost, Intel's new photodetectors have the advantage of being more sensitive, which may further reduce the price of fiber-optic communications. Paniccia said that, due to the increased sensitivity of the devices, they can transmit over a longer distance, or over the same distance with lower-power lasers.

The photodetectors, which are between 30 and 50 microns in size, work by multiplying the optical signals they receive. Photodetectors work by capturing a photon (a quantized particle of light) that comes in and is absorbed by a material, which then converts a photon into electrical energy (an electron).

In Paniccia's avalanche photodetector, the electrical energy produced is amplified by a "multiplication layer", which uses ionization to turn one photon into as many as 100 electrons. Those electrons then get separated by applying a voltage, which produces a current, similar to a solar cell.

Paniccia's team is currently able to demonstrate devices with speeds of up to 40Gbps, with as much as three times more performance (gain) than today's best detectors. However, the team has also been able to demonstrate devices with up to 200Gbps throughput.

"Now we have actually shown a device that far out performs anything in indium phosphide," he said. The device can be optimized for speed (Gbps), or efficiency over distance (meters per watt).

The work of Paniccia and his colleagues has been published in the journal Nature Photonics, and was conducted in conjunction with Darpa, Numonyx, the University of Virginia, and the University of California.

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