And yes, the transmitters will need to be powerful enough be a distinct signal over the background of the star that is in the line of sight of the receiver / beyond the transmitter.
My understanding is that's a solved problem - NASA's Deep Space Optical Communication has demonstrated laser communication even with the sun in the background. Laser wavelength and modulation are noticeably different than a stars noise if you filter and just look for the wavelength and modulation of the laser, which is notably shorter and faster than most of the noise coming from the star.
Maybe, but if your probe is heading directly towards another solar system then it will be backlit by its destination.
https://space.stackexchange.com/questions/33338/why-is-the-o... is a neat question that addresses this issue.
And yes, the transmitters will need to be powerful enough be a distinct signal over the background of the star that is in the line of sight of the receiver / beyond the transmitter.
My understanding is that's a solved problem - NASA's Deep Space Optical Communication has demonstrated laser communication even with the sun in the background. Laser wavelength and modulation are noticeably different than a stars noise if you filter and just look for the wavelength and modulation of the laser, which is notably shorter and faster than most of the noise coming from the star.