Scott,
Did you have any trouble with temperature-sensitivity of the optical filter?
When doing experiments at 633 nm (He-Ne red) I had to use a narrow band filter
to keep that part of the ambient light out of the photomultiplier, even though
the lab was lit with a mixture of blue and green fluorescent tubes to minimise
the amount of red.
The first attempt did not work at all. The photomultiplier was cooled with dry
ice* and the optical filter pass band shifted too much. I had to isolate the
PMT and the filter with some optical fibre to keep the filter at room
temperature.
73
John F5VLF
* a bit below the temperature you get in winter I think
On 8 Oct 2011, at 23:14CEST, Scott Tilley wrote:
> Hi Stefan
>
> I've created a wide-band audio link before using a laser. In fact, I used it
> to bounce the audio I wanted to send off of a passive reflector. Wideband
> and excellent fidelity is possible, just ensure the object you are bouncing
> off is very stable otherwise you'll get microphonics (useful if you want to
> hear what's going on somewhere else :-)........ I strongly recommend the use
> of a very narrow band interference type filter for the laser wavelength you
> are using, mount this over the PIN diode detector... This way the system is
> usable day or night without noticeable degradation due to sunlight.
>
> 73 Scott
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