Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



Laser Pointer Store

Maximum laser frequency

Wolfman29

New member
Joined
Jan 14, 2011
Messages
3,830
Likes
200
Points
0
Basically, what I was saying is that you will need some sort of detector that can sense near-infrared. You can't just use your normal, everyday photodiode or something, but something that will produce a signal when it detects the 808nm light.
 

Wolfman29

New member
Joined
Jan 14, 2011
Messages
3,830
Likes
200
Points
0
I wouldn't think so - Look at the rise/fall time. In order to achieve 100MHz, you need your total rise/fall time to be less than or equal to 10nS for all of your components combined. The rise/fall time on that phototransistor is 3uS, which is 300 times slower than you need.
 

ITman496

New member
Joined
Aug 19, 2011
Messages
185
Likes
9
Points
0
That looks expensive.. lol

I've found that when they ask for quotes, its not a good sign. :p
 
Joined
Sep 22, 2007
Messages
977
Likes
57
Points
0
The complete equipment already exists but you have to look on the telecom side of the house. All telecom backbones are now serviced by Optical Carriers (OC). You may have heard of OC-3 or OC-12 or OC-192 or even larger pipes. These numbers indicate the bandwidth of the fiber carrier. Telecom laser systems are in the 1300nm range and utilize single longitudinal mode laser diodes with laser photodetectors. As with everything else in telecom there is a transmit side and a receive side. Removing the fiber in between and using optics simply shortens the distance it can transmit. The fiber acts as a waveguide allowing transmission many kilometers away. The signals are picked up by repeaters and retransmitted.

Laser diodes are semiconductors and switch at semiconductor speeds. Furthermore, laser diodes do not suffer from the delay caused by spontaneous emission as seen in LEDs once the laser reaches threshold.

Because the technology is common place you will probably have many resources available to build your point to point communications link. It's been done using analog modulation to transmit voice and exists to in telecom form to transmit data. If you are familiar with communications protocol stacks you can really transmit in any form you wish as long as it's compatible with the layer 1 (light transmission).

Building it with home made components may only force you to a lower data rate but it should be a good project and should work.
 

ITman496

New member
Joined
Aug 19, 2011
Messages
185
Likes
9
Points
0
Sounds cool! It seems the only doubt so far is a receiver that is fast enough. For cheap enough.

..maybe I should see if I can strip the components of an old fiber switch that we don't use anymore.
 

ITman496

New member
Joined
Aug 19, 2011
Messages
185
Likes
9
Points
0
Yeah, he sounds like he knows his stuff, lol.

Still. Do you think that 10ns thing I found for only ten bucks each would work? Because while the one you found is perfect, its probably rather.. expensive.
 

Wolfman29

New member
Joined
Jan 14, 2011
Messages
3,830
Likes
200
Points
0
Well, the problem is is that the rise time is 10ns AND the fall time is 10ns, meaning that you have, at most, 50MHz, if you have no other delays in your system.
 

ITman496

New member
Joined
Aug 19, 2011
Messages
185
Likes
9
Points
0
Hm, maybe I could divide it into two lasers.

Though I wish I could use that one you suggested. I don't even know how to get it though, lol
 

millirad

New member
Joined
Apr 28, 2009
Messages
2,581
Likes
114
Points
0
Frothy got that right! Don't reinvent the wheel. Fiber has been engineered to transmit data and can't be beat compared to air as the medium. Especially with simultaneous packet transfers. :)
 
Last edited:

ITman496

New member
Joined
Aug 19, 2011
Messages
185
Likes
9
Points
0
I'm not trying to beat fiber, lol

This is just a small experiment to try to make an optical based network thing cheaply

And besides, this doesn't need cables.
 

Kmor2004

New member
Joined
Jun 12, 2011
Messages
292
Likes
13
Points
0
Not likely, or I'm just misunderstnading your idea of dividing it into to 2 lasers.

Oh, and there are old school tubes that can switch in the low nS region but I beleive thye are extremely rare, and even if you could get a hold of one you might catch the attention of certain law enforcement agencys.

Found em http://en.wikipedia.org/wiki/Krytron
 
Last edited:

ITman496

New member
Joined
Aug 19, 2011
Messages
185
Likes
9
Points
0
...haha

Nah, don't wanna get arrested for making a laser network..

Maybe for now I can just do 10mbps connections, and then get faster in revision 2?

It can't be hard to find something that switches in 100ns.. right?
 




Top