Communications of the ACM
Light and Sound Together Might Be Just-Right Wireless Solution
A combination of free space optics and millimeter wave technologies appears to provide the best of both worlds in high-speed, high-capacity wireless communications.
Credit: ExtremeTech.com
The history of high-capacity wireless communications is littered with ideas that sounded great in concept, but never quite panned out.
Taken separately, free space optics, or laser communications technologies, and various radio-based solutions, including microwave and millimeter-wave, have all had their champions over the years, yet each has had shortcomings that precluded them becoming a dominant solution to filling in networks' needs where the fiber runs out.
AOptix, a Campbell, CA-based company, however, is attracting attention with its combination free space optics/millimeter wave technology, which it says provides the best of both worlds in high-speed, high-capacity wireless communications, while eliminating the shortcomings of each.
"Every wireless technology is going to have some susceptibility to weather," Christina Richards, vice president of marketing for AOptix, said. "Radio frequency technology is going to get a significant amount of rain fade if it's going over distances that are longer than the technology can actually handle. And if you're talking about free space optics standing by itself, it will be affected by fog—the second you have water molecules in the air, you split the light and lose your signal."
The AOptix technology, which provides a symmetric two gigabits per second (Gbps) capacity, takes advantage of both technologies by transmitting redundant data streams up to 10 kilometers at a hop in both wavelengths. At the receiving end, proprietary algorithms discern which packets are the strongest, regardless of which medium they came across, and combine them into a unified data stream.
"It's the first time people have really successfully put two complementary wavelengths together," Richards said. "You have your light wavelengths in terahertz and radio wavelengths in gigahertz working together where one is strong and the other is weak."
While the technology is not new, ever-increasing demands for data capacity at the last mile and between fiber hops are bringing laser-radio to the fore.
"One obvious use case is backhaul," Ron Kline, a principal analyst with technology research and consulting firm Ovum, said. "The other is low-latency interconnection. It would work in any kind of backhaul, but from a demand perspective, mobile is the big one. Any kind of last-mile access, if you're an enterprise and didn't have any sort of connectivity, this would be a solution. The benefit here is really where you can't put fiber. The cost of fiber has come down significantly, but there are some places you just can't put it."
Astronomical Origins
Founded in 2000, AOptixhas its roots not in communications, but in deep space: the company's founders, two astronomers, employed a technology called curvature adaptive optics, based on specialized mirrors that change shape thousands of times per second to compensate for the distortion of light as it passed through the atmosphere, while working at the Keck Observatory in Hawaii.
They shortly thereafter began bringing the technology a little closer to earth, working with the U.S. Department of Defense and the Defense Advanced Research Projects Agency (DARPA), creating high-speed communications networks in more contexts than one: not only was data transferred at the rate of 80 Gbps, it was done between aircraft moving at up to 600 miles per hour. It was while designing these aviation-based networks that they perfected automated link alignment and beam steering technologies that compensated for weather conditions, access point movement, and other anomalous factors.
Kline said he tested a free space optics-only technology many years ago, when he worked for a regional telecommunications company; that technology failed because it was unable to compensate for building sway over a distance of about a half-mile/one kilometer. However, he said he has seen both demo and live versions of the AOptix technology, which compensates for up to 3 degrees of building sway and weather factors, impressively withstand both shaking and climatological elements.
AOptix has reported deployments worldwide, including one by Mexican bandwidth wholesaler Car-Sa, and another in a 7-km. link from submarine fiber-optic cables coming into the coast of Africa to central Lagos, Nigeria. In the U.S., the technology is being deployed by Chicago-based Anova Technologies, a network service provider of exchange-to-exchange connectivity for financial markets.
"Initially, our strategy was to use low-latency fiber connectivity with low-latency opto-electronics on the fiber," Anova chief technology officer Kieran Athy said. "Interestingly enough, bits travel through the air about 50% faster than over fiber—30% of that is just because of the physics, and there's about a 20% improvement because you can go as the crow flies."
Deployment
Anova has been trialing the AOptix technology for about a year, has run one production link for about six months, and is about to deploy it in links between Nasdaq in Cartaret, NJ, Intercontinental/New York Stock Exchange (NYSE) in Mahwah, NJ, and BATS Global Market facilities in Secaucus, NJ.
"With all sincerity, we're really excited," Athy said. "We're seeing what we wanted to see from this technology. It's doing what we thought it would. In weather conditions that knock out millimeter-wave, it performs, and there is no lost transmission. It's not switching over, it's simulcast."
While point-to-point and backhaul are the leading-edge deployments, Athy also said he could see where the laser-radio technology might be employed in densely built-out urban business districts (where fiber is also expensive to put in) or in education or medical networks.
AOptix' Richards conceded such a promising technology field would appear to be ripe for competition, but likes the company's position.
"We do have some advantages working in our favor; things like the eight years of working with the Defense Department to work out certain technical challenges other people don't have the benefit of, and that would be hard for them to replicate," she said. "So there's a pretty strong barrier to entry compared to other technologies. But there are a lot of smart people out there; somebody else will be able to figure out how to do it as well. But by that time we'll have a big footprint."
Gregory Goth is an Oakville, CT-based writer who specializes in science and technology.
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