Communications of the ACM
Getting Light-based Internet Right
Even as a standards battle has slowed market uptake of LED-based Li-Fi, developers and manufacturers are looking at switching from LEDs to laser.
Credit: hacktronics.co.in
With apologies in all the right places, here's an imaginary publicity stunt from six years ago:
Voice- over: Shuji Nakamura, you've just won the Nobel Prize for co-inventing the blue LED. What are you going to do next?
Nakamura: I'm going to lasers.
Around that time, light-emitting diode (LED) pioneer Nakamura was heavily involved in an LED company he started, Soraa. Fast forward to today, and you will find him and his latest company, SLD Laser (which Kyocera has committed to buy), advancing laser technology in a manner that could bump LEDs aside and usher in the new new future of lighting: laser diodes.
While that holds for lighting's traditional role of illumination, it is equally the case with lighting's newfangled aspiration to become a wireless data communications conduit, known as Li-Fi.
In fairness, Nakamura has long had a passion for both technologies. He is credited with inventing the blue laser diode used in Blue-Ray discs, but it seems his favorite "child" these days is the laser, not the LED.
A quick review: In case you hadn't noticed, LED light sources, with their energy efficiency and longevity, in a relatively short period of time have replaced the filament and gas bulbs that had ruled the lighting world. Nakamura was one of three co-inventors of the blue LED diode, which catapulted LEDs into general lighting, an accomplishment that jointly won them the 2014 Nobel Prize in physics. Before blue, LEDs were relegated to more pedestrian duties, such as instrument panel lighting.
With their emergence as light sources, LEDs are beginning to take on other duties. Because LEDs are semiconductors, they lend themselves to a variety of digital operations, such as transmitting Li-Fi signals using modulated LED light waves, rather than the radio frequencies of Wi-Fi. Li-Fi enthusiasts believe the technology will go a long way to alleviating the bandwidth crunch of Wi-Fi, while also offering more secure networks, among other advantages. Think of it as fiber optics without the fiber.
Yet for various reasons, LED-based Li-Fi has been slow to take off. University of Edinburgh professor Harald Haas and his Scottish startup pureLiFi began pursuing it in earnest commercially back in 2012. Yet for all of their diligent advances, deployments by pureLiFi and its LED competitors have so far been limited to a relatively low number of small installations. A standards battle is slowing market uptake, and gadget makers have balked at embedding Li-Fi chips the way they did with Wi-Fi.
Enter Nakamura's SLD Laser and other laser companies, who might as well be singing the Irving Berlin show tune Anything You Can Do (I Can Do Better).
"Any motivation to want to use Li-Fi to begin with is really the reason that one would want to ultimately go with laser Li-Fi," says Paul Rudy, another co-founder of Santa Barbara, CA-based SLD, where he serves as senior vice president of business development. "Laser has substantially higher speed capability. You're talking about orders of magnitude faster than any LED."
Chao Shen, co-founder and technical lead of SaNoor Technologies, the Orefield, PA-based [LF1] spinout of Saudi Arabia's King Abdullah University of Science and Technology (KAUST), picked up the thought. "There are many advantages to using lasers," Shen says. "One can have 100 times higher speed and 100 times longer transmission distance when using laser Li-Fi in comparison with LED Li-Fi."
The man regarded by many as the "Father of Li-Fi," pureLiFi's Haas, sees the technology's future in laser light, despite having a vested interest in LED Li-Fi. Haas cited several reasons why lasers will emerge, with speed among them.
"It can go an order of magnitude faster; I see a clear path to 100 gigabit per second (Gbps) in the next year or two," says Haas, a professor at the University of Edinburgh in Scotland, where he is chair of mobile communications. In comparison, 100 Gbps is 100 times faster than the 1 Gbps that Haas' pureLiFi has experimentally demonstrated in public using LEDs, and probably 400 times faster than what LED Li-Fi has achieved in any practical setting.
Light is the new data.
Not to be lost in all of these data comm attributes is the notion that many of these laser companies are also developing lasers as general illumination sources, and believe that lasers, sooner than many people think, will supplant LEDs in lighting's traditional role. SLD Laser, for instance, already offers lasers in flashlights and automobile headlights; SaNoor has built them into desk lamps.
SLD Laser has been hitting data rate milestones in the lab at a blistering pace over the last year, having already surpassed the 20 Gbps it demonstrated at the CES consumer electronics show in Las Vegas in early January. "A year ago we were at 10 Gbps, then a couple of months back we were at 20 Gbps, and now we're at 30," says SLD's Rudy, who foresees hitting 100 Gbps in a year.
Drones, planes, and automobiles.
As with any technology, the pilot and commercial products lag behind the lab results. But there too, SLD has been moving right along. The company planned to provide development kits this year for cellphone-sized laser modules that deliver data at between 1 and 2 Gbps, over distances up to around 100 meters, as well as offering a larger module (about the size of a big kitchen toaster) that delivers rates of 10+ Gbps over distances of up to around a meter.
There seems to be an incipient appetite for these things in a world that is growing ever more data-intensive, and wireless to boot.
Rudy says the smaller, longer-range kits will ship to developers in the autonomous vehicle and avionics industries, who are keen to test their ability to transfer everything from data about their own performance to data they are collecting, to content they have to transmit (such as, for example, hundreds of different movies and audio recordings onto a commercial plane). "Airplanes are like huge autonomous vehicles at the end of the day," says Rudy. "They have boatloads of sensor data of information of how the plane has performed, of its plans for the next loop. There are bottlenecks, and that community is excited about Li-Fi. Some of it is current need, and some of it is future need."
The same holds true for developers of drones, and of the land-based autonomous vehicles that will increasingly be tasked with transporting goods and people, he says. "These vehicles have terabytes of data being stored in them needing offloading or slurping up. They have tons of sensors. They may need to dump the data content, terabytes of data, and they may need to do that in as short a time as possible."
Rudy envisions laser Li-Fi as the conduit for rapidly transferring voluminous data on deliveries, inventory, and vehicle performance, with the overall objective of improving a vehicle's economic performance and safety. "The autonomous vehicle community is really excited about it," he says, noting that non-disclosure agreements prevent him from revealing the names of trial partners or customers.
The same enthusiasm is running through the factory-of-the-future community, says Rudy, where laser Li-Fi will transmit updated instructions to machines and robots, and will be the conduit through which those machines and robots feed back information on their tasks and performance, providing constant insight on how to maintain and improve operations. "The more these factories of the future become autonomous, the more the data needing to be exchanged is required," says Rudy, who envisions "light spraying data down to various mobile machines moving around."
Light will play a role where radio frequencies such as those in Wi-Fi, cellular, and other frequency ranges cannot, because the light waves will not interfere with machinery the way radio frequencies can.
Underwater world
SaNoor is equally avid about the laser speeds and feeds, and has a particularly strong interest in underwater applications. The KAUST-connected company already is working with Saudi Aramco in the Persian Gulf, developing laser-based receiver and transmitter modules with sensors to help transmit and download the voluminous data collected by robots, unmanned vehicles, and human divers that are monitoring the state and performance of marine pipelines, rigs, and the like.
"The ultimate goal is to enable the underwater IoT (Internet of Things): the IoUT," says Shen. "Most of the data will come from collecting data from sensors. You can collect the videos or the pictures from the inspection vehicles."
A good bit of the data eventually would be downloaded from onboard storage devices to terrestrial servers. Gathering it in the first place for ultimate downloading marks a huge advance in what Shen said is typically a very low-tech, almost paper-and-pencil process of recording observations.
"We gather real-time data from the drilling, from the underwater vehicles, from monitoring the pipelines, for example," Shen says. On top of that, laser Li-Fi serves an underwater communication network between robots, "So our communication system will improve the efficiency of the data harvesting process," Shen says. "Whatever the data it is, whether it's exploration data or maintenance data, we link them together."
Also underwater, SaNoor is participating in Red Sea explorations to help gather data on coral reefs and other marine ecology. In another market, the company is in early discussions with Norwegian fish farms to possibly deploy the technology there.
Like SLD, SaNoor sees 100 Gbps speeds nearly within reach. Shen believes the company will accomplish that data rate within the next 12 to 18 months. It recently demonstrated 35-Gbps speeds in an indoor deployment over five to 10 meters. Similar to SLD, that speed came virtually on the heels of a previous milestone, as the company had hit 10 Gbps only six months earlier.
Says Haas, "We are looking at one terabit per second in the next five years."
Mark Halper is a freelance journalist based near Bristol, England. He covers everything from media moguls to subatomic particles.
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