[Laser] Optimizing sound card modes for optical communication

[Chuck Hast]

On 11/22/06, Art <KY1K at verizon.net> wrote:
> OOK seems to me to be the best, but simple OOK has no communications protocol.
>
> Also, when using OOK, the zero bit (no transmission) is wasteful in
> terms of speed or throughput. By having 2 tones and a constant
> transmission, the mode has better throughput and it's easier to tell
> whether the loss of signal is due signal loss or whether the other
> station is just sending a zero::>
>
> I always considered background noise as a moot point. My soundcard
> does the decoding and NOT my ears::>
>
I am going to date my self with this one.... I have used two TNC's (packet
radio Terminal Node Controllers not the connectors) and used the NRZI
base band I/O to drive the laser and then used the base band output from
a receiver for the receive end to demo data over a optical path.

I have a location on a 23 story roof (where we already have a amateur radio
packet switch) that I want to put a laser tranceiver on, I will add it to
the switch  as a additional port. then if I can add some remote aiming
I would be able to take the other end off to places and try to bring up
optical paths. I have all of the HW I need except he az/el remote gear
to do this one, I just need the time to do it. Of course this is not low power
testing, but it is more than anything else testing the concept of a FSO
link at whatever speed I can get out of it and how ever far I can get it to
run reliably. If these things can be used as metro area data links over
several mile paths, that frees up RF resources that can be used for
other things. Now if I can just get me so SIO cards I can get rid of the
TNC's and just run the base band data right straight out of the PC.

-- 
Chuck Hast  -- KP4DJT --
To paraphrase my flight instructor;
"the only dumb question is the one you DID NOT ask resulting in my going
out and having to identify your bits and pieces in the midst of torn
and twisted metal."