[Laser] Laser light extra noise...

[f1avyopto at aol.com]

Hi all
I am also very saddened by this situation.
My goal was not to create controversy but to debate from theoretical arguments, physical and experimental ...
I regret not having been able to get Chris on this field so that everyone can learn from different arguments.
Chris is a pioneer with optical free space communications and his experience and knowledge are remarkable.
But he never wanted to experiment extensively with lasers for ethical reasons almost!
This is unfortunate because it went next to very interesting marginal phenomenons.
I have never questioned the fact that LED systems are less noisy the laser systems for point to point optical links.
It is rather obvious for everybody...!!!
My discussion concerned only scattering properties of special targets, such as clouds, gaz layers or thick vegetation, which can integrate the spatial irregularities of the laser optical beams.
The price to pay is of course a strong lost due to light dispersion and a modulation bandwidth reducing because the diffusing media lenght (The modulation cycle must have a wavelength longer the diffusing size).
In cloud bouce these properties are not different with power LEDs but the energy density, very far away the optical TX can be well better with lasers.
The received global noise is lower because :
- The enlighted area on the sky is more bright and small and so the spurious light from clouds can be very reduced via a matched optical field on the RX.
- The monochromatic laser light gives the possibility of ultra narrow optical bandwidth filtering.(With APD detectors a low background is determinent to assure good SNR)
73
Yves F1AVY


 

-----E-mail d'origine-----
De : Tim Toast <toasty256 at yahoo.com>
A : laser at mailman.qth.net
Envoyé le : Samedi, 25 Septembre 2010 9:56
Sujet : Re: [Laser] Elvis Has Just left the Building


...
Well, it's just sad.. Really, i hate to see him go like that.. 
no reason leds and lasers can't work side by side. Chris obviously 
knows a lot about all this.. but he doesn't seem to be open to new 
ideas in some areas. There's nothing wrong with being wrong 
sometimes. That's how we learn isn't it? I know i've been wrong lots 
of times and i try to learn something in the process. - It is easy 
though to hang on to old concepts about something long after there 
is something new discovered. This stuff is evolving constantly in 
most areas. A theory today might be a fact tomorrow or it might not,
time will tell. If you think somebody is wrong, call them out on it. 
If you have some new idea about something, speak up! At worst, you 
could be wrong. At best, it may lead anywhere.

I don't harbour any ill will towards Chris. I wish him well and 
he's welcome back anytime

tim toast
 
>
> "There won't be a next time. I've unsubscribed. The ignorance 
> is too much for me to waste more time on it. Enjoy. Cheers. 
> Chris VK3AML"
>




      
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