Skip to comments.Chinese professor builds Li-Fi system with retail parts
Posted on 11/05/2013 9:44:44 AM PST by Utilizer
Chinese professor Chi Nan has built her own Li-Fi wireless system that can use LED lights to send and receive Internet data.
"I bought the lights from Taobao," she said, referring to the Chinese e-commerce site.
The professor from Fudan University showed off the technology on Tuesday at the China International Industry Fair in Shanghai. Unlike traditional Wi-Fi routers that use radio signals, Chi's system relies on light to send and receive data wirelessly.
Others scientists, especially in the U.K., have also been researching the technology, and dubbed it "Li-Fi". But rather than develop specialized hardware, Chi bought off-the-shelf retail parts to create her system.
(Excerpt) Read more at networkworld.com ...
Isn’t that part of Obamacare marketing?
Light is RF.
And any network is only going to be line-of-sight.
Light doesn't pass through walls.
I built something very similar back in Jr HS.
Another Chinese scam looking for funding.
Old tech for networking. Limited to line of sight. Limited throughput. Used IR.
Beg to differ, mate. Started out on CB transceivers, and 27MHz RF is not "Light" by any stretch of the imagination.
As far as not passing through walls, for between rooms all you need is a light pipe with convex ends. Or an Active Repeater, if you do not mind the latency. External, who doesn't know what an "Antenna" is?
Why do you say Light is RF?
Can you express your frequency ranges for each?
IR has gotten quite a bit more refined and powerful these days, and Blue LEDs (or ultraviolet) have greater inherent bandwidth.
By off the shelf, is this simply taking a fiber-optic card, attaching external LED (CREE 4 for some real throw), and directing it over line of sight?
Nice idea. Android app for sending and receiving Morse works similarly, if brightly using the camera’s led flash to emit.
Best possible use would be point-to-point pipe between separate buildings.
LEDs are already pretty strong off-the-shelf, and look at the inherent range a simple LED flashlight already has.
I toyed with the idea of building something like this, but I was thinking of using LED’s for signal acquisition and off-the-shelf CD-player IR lasers for high-bandwidth transmission. The CD auto-focus mechsnism would have to be adapted to multiple-axis pointing and focusing.
I have five and ten gigahertz transceivers, and none of them can detect light at any frequency.
The directionality of this could be interesting, but for that, I would go with a modulated low power laser.
Radio waves and light are just different wavelengths on the electromagnetic spectrum.
A photodiode can of course detect light, but good luck getting any bandwidth out of it (grin). I think CD laser pickups are the way to go since they give you almost everything you need.
He said light was RF. He did not say all RF was light.
I was thinking more along the lines of a cheap five-LED flashlight or several from the Dollar store for a directional beam, add some cheap 2N2222A transistors (about 10/ dollar) and an electret mic for quick and dirty Amplitude Modulation, and if you want to get a bit more fancy, add different coloured filters to the white LEDs to define different bands for separate data streams. Sounds rather fun, now that I think about it.
In this case, wouldn't it be Ri-Fi ??
Bad joke aside, you're right in that it's all EM radiation ...
Actually, most LEDs can also detect light, if not as strongly as dedicated devices can. I used to work in R&D in Electronics as well as Production Engineering. Quick and dirty, a clear plastic lens in front of the LED to bring up the sensitivity and you can accomplish quite a bit. Just factor in a very low amplitude and noise filtering and simple functions / commands work just fine.
But you're right. Your shortwave receiver won't pick it up, because it's tuned to a different range of frequencies.
Hmmm. Never really worked with Optics all that much, but I shall try to think about how to detect the ElectroMagnetic emissions of a light source a bit more as opposed to the optical emanations of a device.
Here’s another thought...UV LED’s are readily available. You can boost your bandwidth just by going to 250nm.
Maybe it should be Li-Fi-Fi.
Why does Network World have to be excerpted? It’s taking more than a minute to load all the ads and horse crap on that site.
Trying to find out how fast it would operate...
Li-Fi, however, could be deployed in everyday LED bulbs, with light-based Internet connections covering the interior of entire homes or buildings. The data connection speeds can also reach several gigabits per second. Chi’s own system runs at 150 Mbps by using a small number of LED bulbs each at one watt.
“With a more powerful LED light, we can reach 3.5 Gbps speeds,” she added. Both the router and receiver are fitted with LED bulbs so that they can send data, and also installed with a chip that can process the signals.
Because it is dependent on light, the technology can’t penetrate walls or work in complete darkness.
***Wouldn’t complete darkness make an LED based system work BETTER?
I can FReepmail you the article essence if you wish, but I always make it a habit to excerpt for the sake of brevity and to keep the bandwidth down.
Your confusing Electromagnetic with RF. Xrays are electromagnetic that doesn’t mean your transceiver can pick it up because it isn’t tuned to the frequency in question - just like it isn’t tuned to pick up the visible light spectrum - it is all electromagnetic waves. RF is one subset of frequencies in the electromagnetic spectrum.
” It used to be a science project experiment with a light bulb that flickered when you spoke into the microphone and a receiver that used a photocell to convert the amplitude-modulated light waves into an electrical signal that would be amplified and output to a speaker.”
Hmmmm,,, Seems just about like the Tremolo/Vibrate-oh in my 64 Fender Vibroverb! But we call the parts “The Roach.”
The optical emanations of a light source ARE electromagnetic emissions.
The history of our understanding of the electromagnetic spectrum is full of very interesting discoveries.
Maxwell in the 1800s was able to use the known properties of electric and magnetic fields to derive the speed of propagation of electromagnetic waves. Remarkably, the speed matched the already known speed of light. It was this "coincidence" which suggested later experiments which established that light was indeed a form of electromagnetic wave.
What has been traditionally referred to as "short wave", the neighborhood of 40 meter wavelengths, turn out to be some of the longest waves that one deals with in the various uses of electromagnetic waves. Light waves have wavelengths around the diameter of an atom, say about 1 angstrom.
One angstrom is 1e-10 meters, which means one-tenth of one-billionth of a meter. Now that is really a "short wave".
The reason why light doesn't penetrate the walls of a house is related to its wavelength. The close match between the wavelength of the light and the size of the atoms making up the wall causes a greater amount of interaction of the light with the wall. This is seen in the form of absorption of the light and conversion to heat or the reflection of the light.
The transparency of a window is due to the fact that much visible light is able to penetrate the window with very little interaction with the atoms in the window. In a similar fashion, radio waves of much longer wavelengths are able to penetrate walls because of the fact that they interact very little with the atoms in the walls.
Yes, so visible is not considered RF.
They are both on the spectrum of electromagnetic waves.
Unless you’re an engineer like me.
Anyway, nothing worth arguing over.
Would this not be much more secure, in that the broadcast area of light can be better contained?
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