Hi,
What information did we get?
* 2 devices
* 10 cm
The rest is guessing.
What we don't know:
* why no copper cable? This should be the most obvious solution.
* what type if data? Digital, analog? What source? Temperature? pictures?
* what data rate? For one application "10Mbaud" is low, for the other application 9600 baud is high...
* moving objects or still objects? (If moving: how fast? Linear, rotating...)
* in free air? (It could be in water swimming, in space...)
* a barrier between the two objects? What material?
* optical / Ir, electromagnetic / RF, ultrasound..
Klaus