>    For the receiver I'm thinking about using a small telescope, pointing
>    it to the transmitter (hopefully 1+ Km away.. ehm). Will the lens be
>    transparent for the incoming 875nM or 950nM light?

People get considerably more range than that using LEDs in continuous
operation (eg voice) communicators.
Some have heat sunk LEDs which were not intended for heat sinking to allow
higher than spec average powers. If you google for long range free space
optical communications you are liable to find some. This application turns
up in hobby magazines every 5 years or so - I recall having seen 3 or 4
such. Optics make a considerable difference. Aiming gets very hard. Even red
rather than IR LEDs have been used over distances of this order and it does
simplify aiming.



        RM

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