Let’s say that, via some method that doesn’t really matter here, we find conclusive proof that there is an advanced and intelligent alien civilization inhabiting This Expolanet of That Star, which is, say, five light years away. Could we communicate with them via existing technology? Or would whatever signal we sent them degrade and be useless across that much space?
I don’t know the answer to your question, although the SETI people certainly think so. But even if it were possible to exchange symbols, can you imagine how long it would take to establish a common language if any exchange took ten years back and forth?
The internet tells me that the two Voyager probes transmit with a power of 23 watts, and we are able to receive their signals with 10^-18 watts on Earth. The probes are 0.0025 light years away, that’s 1/4000 the distance of your ten light years star, so the law of inverse square would tell us that the signal would have to be sent from the other end at 23 * 4000^2 watts. That’s 368 megawatts. That’s an awful lot of power that would have to be pumped just into transmission, about a third of the power of a nuclear plant just in terms of electromagnetic signals. On the other hand, I would guess that we’re not pointing our most sensitive receivers at the Voyager probes.
You got something better than the Deep Space Network?
Though of course, we could make something better, if we had reason to.
For perspective, there are about 12 star-like objects within 10 light years of Earth, including the Sun and including 4 or 5 brown dwarfs (failed stars).
That calculation assumes that the Voyager probes are right at the limit of what we can detect, and we could not detect anything fainter. I doubt that that’s true.