[Laser] PIN diodes and Noise floor

[Andrew T. Flowers, K0SM]

I have a question for folks who have played around with PIN diode 
detectors--

I've put together a few of the K3PGP front ends now and I'm really 
looking forward to getting my laser diodes going for a complete 
tranceiver system.  Anyway, I was wondering if the PIN diode dark 
current is much of a factor under actual nightime use?  Is the noise 
floor coming from ambient light or from the diode itself?  I imagine 
this will depend largely on how big of a lens you are using, and how 
clear the sky is, but I'm trying to get a ballpark figure.  John 
mentions that cooling the diode improved the NF, e.g. putting it in the 
freezer for a while, but does that really matter practice?  Does ambient 
light drown out the dark current?  I'd test this myself, but it's not 
easy for me to get away from city lights.

Andy K0SM/2