[Laser] Notes on Luxeon I, III's and Rebels and Phlatlights (C. Turner)

[Dave]

On 2010-09-17 12:00 PM, laser-request at mailman.qth.net wrote:

> Date: Thu, 16 Sep 2010 14:05:50 -0600
> From: "C. Turner"<turner at ussc.com>
> Subject: [Laser] Notes on Luxeon I, III's and Rebels and Phlatlights
> To: laser at mailman.qth.net
> Message-ID:<4C92789E.8060807 at ussc.com>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Hello again,
>
> I would concur with what Chris said about the Luxeon III/Rebel LEDs and
> Phlatlight modules.

<snip>

> In the year or so since they've been operational I've been able to get
> time to do only limited testing of the units that I've constructed, but
> they do work very well.  One problem (and it's not a terrible problem to
> have!) is that fact that run at full power, full-duplex communications
> is unlikely to be possible on a weak-signal path owing to "desense" from
> scattering (Rayleigh, Mie, etc.) of the transmit beam and it's
> contamination of the "receive" beam:  At full power, my detectors
> experience a dramatic increase in noise floor and may, in fact, suffer
> from a degree of overload.

I assume you've been using the red LEDs.  Have you considered using
some of the other colours available, and doing colour filtering on the 
receive
side to avoid the problem with backscatter?  I'm pretty sure that the 
efficiencies
of the other LED colours are not as good as with the red, though (Plus, 
there's
the issue of receiver sensitivity.).

I suppose another alternative may be to use a digital system, and use a
TDMA type of approach, or a CSMA type of approach, although these aren't
really full duplex.

<snip>

> 73,
>
> Clint

Dave