Xref: utzoo sci.electronics:18324 sci.optics:126
Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!usc!apple!olivea!uunet!wsrcc.com!wolfgang
From: wolfgang@wsrcc.com (Wolfgang S. Rupprecht)
Newsgroups: sci.electronics,sci.optics
Subject: Re: Laser diodes/ optics (esp. IR)
Keywords: Lasers,Infra-red,optics
Message-ID: <1991Mar10.074309.27070@wsrcc.com>
Date: 10 Mar 91 07:43:09 GMT
References: <1991Mar5.164506.18567@gdt.bath.ac.uk>
Organization: Wolfgang S Rupprecht Computer Consulting, Washington DC.
Lines: 22

In article <1991Mar5.164506.18567@gdt.bath.ac.uk> ee8kh@gdt.bath.ac.uk (K House) writes:
>I'm currently undertaking a small project using Infra-red LEDs to transmit 
>information over distances of about 50 metres (through air).
>However, the range I am currently achieving is not really high enough for the
>application I have in mind and so I am toying with the idea of using laser 
>diodes as emitters instead of the diodes I am using at present.

If you just want to carry audio freq stuff you can also try a plain
old flashlight bulb.  Just bias it to the normal operating voltage,
and then modulate it with the signal from there.

The purist will notice that this is non-linear as all heck.  True.
Just keep the modulation to low levels.

One 6" reflector, and a 3 watt bulb, for the xmitter, and a 5 mm^2
photodiode, a 3" lens, and a 536 fet op amp for the receiver will
allow you to send telephone quality sound several hundred meters.

-wolfgang
-- 
Wolfgang Rupprecht    wolfgang@wsrcc.com (or) uunet!wsrcc!wolfgang
Snail Mail Address:   Box 6524, Alexandria, VA 22306-0524