Optical Cellphones

foondog writes "Here is a story over at News.com about optical cellphones. It seems that the Department of Defense has given a grant to the University of California to develop optical cellphones that are faster and more secure. This sounds a little strange to me since you would need a line of site with no obstacles in the way to use this. The article doesn't explain how this might work."

Comments

LOS

[Wyatt Earp]

"It seams that the Department of Defense has given a grant to the University of California to develop optical cellphones that are faster and more secure. This sounds a little strange to me since you would need a line of site with no obsticals in the way to use this. The article doesn't explain how this might work."

What about from a soldier/spy/diplomat straight to a comm sat?

It's easier to get line of sight to orbit.

Re:LOS

[FatHogByTheAss]

You're kidding, right? You can't possibly be this uninformed.

Do you have any idea how much laser power is needed to nail a geosynch sattelite?

Very little. 1500 mJ, specificaly. It's done every day.

let alone burn through the atmosphere and any possible cloud cover.

Uhhh... only if you're in the visible light spectrum. Some wavelengths will pass right through clouds (and other objects, like the earth) completely unphased.

Or how about the laser platform aiming and stability? a shake of less than 0.01mm in the sattelite will make the beam dance around on the planet over a 1 square mile area.

How about it? Do you know we bounce lazers off mirrors on the moon that are about a meter wide, and we bounce the same lazer off satelites all the time.

Not.. no way, no how... not sattelite.

Better call University of Texas and tell them to knock it off, because apparently, what they are doing can't be done.

Here's a quarter, kid. Go buy a clue.

Re:LOS

[tomhudson]

The right-angle mirrors (the ones left by the Apollo missions) on the moon are about a meter wide, but the laser beam, at least for the Apollo experiments, was about 2 miles wide when it got to the moon. Even collimated laser light spreads as it travels.

Can you see me now?

[Anonymous Coward]

(sorry... had to be said)

Using a laser?

[bunyip]

Need line of sight. DoD likes lasers. Big lasers, with lots of power. Could be dangerous.

I wouldn't want to hold one of these up to the side of my head and start talking, it might make it's own line of sight to the nearest tower.

Ouch!

Is this UWB? Are they confusing light with all EM?

[Erpo]

A different technology in widespread use employs a method called wavelength division multiplexing, in which each cell phone uses a different wavelength of light, according to the researchers. In contrast, optical CDMA would encode each pulse, or bit of information, across a segment of wavelengths. The receiver uses a key to decode the signal and re-create the original pulse.

This sounds a lot like Ultra Wideband to me. Also, I'm guessing from reading the article that the author is confusing visible light with radio EMR.

Re:actually, no.

[spike hay]

X-rays are light energy, and they don't seem to have a problem passing through.. well.. you, among other things.

Um, xrays, gamma rays, optical light, radio waves, and everything else is electromagnetic radiation. The penetration ability changes with different wavelengths. Low frequency, long wavelength radio waves penetrate through objects very easily, this is why 2.4 ghz 802.11b goes through walls better than 5 ghz 802.11a.

Higher frequence microwaves, infrared, optical, and UV em radiation is basically line of sight. Ultra high frequency, high energy, sub microscopic wavelength xrays and expecially gamma rays can penetrate most materials due to their high energy.

The East German secret service used this

[uradu]

Not an actual cell phone, but a point-to-point intercom involving binoculars and infrared transmissions. The voice was converted to (analog) IR light and transmitted through optics that created a very narrow beam. At the other end, the IR receiver was mounted in the eye piece of the binoculars and converted the light back to sound. The two devices had to be aimed very accurately at each other. That way a spy in the west could communicate with his pimp in the east across the border with very low probability of interception. They actually had this on the History Channel a few years back.

Optical Communications to Keep Bombs Away

[Crispin Cowan]

This kind of technology is particularly important to the Army for men in the field. The reason is that in the near future, any kind of broadcast RF will result in a bomb down your shorts in a big hurry: smart weapons will home in on any radio frequency they can find, and destroy it. Thus talking on the cell phone, walkie-talkie, whatever, will mean instant death to a soldier.

Thus the Army must have some kind of non-broadcast communications system. I have no direct knowledge of how they would do it, but it isn't hard to imagine. For example, suppose low-flying satelites broadcast a signal. Handsets on the ground listen for that signal, and then point a highly directional antenna (LASER, focussed RF or microwave, whatever) at the satelite, and then starts transmitting a narrow beam.

There is not enough economic motive to develop this for purely commercial purposes. But once it is developed for the military, the commercial benefits are there to deploy it. Directional signalling means much less interference, and therefore much less consumption of precious spectrum, and less need for those pesky and expensive cell towers.

Crispin
----
Crispin Cowan, Ph.D.
Chief Scientist, WireX Communications, Inc.
Immunix: Security Hardened Linux Distribution
Available for purchase

Re:Soldiers Have Been Carrying Optical Cell For Ye

[floydigus]

It's called a heliograph and a CD would make a very good substitute.
Take a CD and an ice lolly stick. Make a hole in one end of the stick and hold the CD up in front of your face, shiny side facing out. Be facing the sun, more or less.
Hold the lolly stick up in front of that (about 12 inches away) and sight through the hole in the CD and the hole in the lolly stick at the aeroplane, boat, visitor craft or whatever you are trying to signal to. Now wiggle the CD until the shadow of the hole in the middle of the CD falls over the hole in the lolly stick. Now you are shining your light right at your target. By flicking your hand, you can turn the light on and off and so make morse. Or binary. Whatever.
If you do do this to a visitor, they will probably just decode the information on the CD and try to work out the meaning. Do not expect to be rescued. Expect instead to get Barry Manilow's greatest hits beamed back to you some days later.
If this saves your life, paypal me! ;)