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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."
"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.
Current cellphones are already operating in bands where line of sight is quite critical to half-decent reception. What makes this feasible is that many surfaces are reflective of a lot of bands of EM radiation. This is why we can see things - they reflect light. This is why you can use your TV remote by pointing it away from the set - it bounces off the wall.
I agree that attenuation will be a big problem, but it's already getting almost that bad as we get higher and higher in the spectru.
Now, if they could only modulate the sun's rays...
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.
If you don't understand any of my sayings, come to me in private and I shall take you in my German mouth.
Optics refers to the range of the electromagnetic spectrum that we can visibly process (400-700nm wavelength). All other wavelengths are not classified as "optical"
The grant is not to make optical cell phones. The grant is to develop CDMA (a technology used in cell phones) to be used in fiberoptic communications. The title is a bit misleading.
So, why so much money to port a technology. CDMA allows more effective use of the bandwidth and as the article points out more security than frequency division multiple access. For radio frequency stuff, CDMA is what nearly everyone uses. For radios it requires a wide bandwidth output stage. That is the kicker. The optics guys use fairly narrow band laser output stages. Then the hook them together on the same cable. They don't interfere because they are at different frequencies. To do CDMA with your whole bandwidth requires a wide bandwidth output solution (either a single broadband output or some way to put multiple lowbandwidth stages together in a better way.)
This is pretty old news.
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I'm going to dub this the 'Laser Phone'. The Laser Phone will not be made for general public use. Laser Phones will be made for military and corporate entities that require ultra secure communications.
You maybe asking: âoeWhy would you need such a clunky method of communication? Line of site is not practical.â
The answer is very simple: Supercomputers and triangulation.
You see any voice communication has certain pitch and volume amplitude modulations. Pitch and volume amplitude modulations are part language and part human physiology. No matter how you scramble and encode the communication the human voice will always have certain keys that can be easily discerned in a conversation.
An enemy can easily grab and record a radio signal. Then the digitally recorded file can be feed in a Beowulf cluster of cheap computers. That data can within a few minutes can decode your voice and thus get your tactical information.
Another advantage of optical communication is that it is almost untraceable. Anytime you use a radio you sending out a beacon saying, "I'm right here; bomb the snot out of me!" An enemy can use simple triangulation to locate you.
A Laser Phone will be virtually impossible to intercept, track, and decode.
BTW: Anyone remembers those World War I movies where the soldiers would use mirrors to send Morse code message?
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