I'm currently diving into this topic and as I understand from the brief search there are two main types of inter-satellite link: radio and optical. As I can see, one of the main distinction of optical link is that we need to configure the direction (as opposed to radio, where we emit the signal broadly). First inter-satellite radio link was established in 1975, first inter-satellite laser link — in 2001. What I don't yet understand is that whether optical inter-satellite link and laser inter-satellite link are the same thing?
If it really is the same thing, then my questions are:
- What are the basic characteristics of such communication channel? Bit rate? angles (which allow to establish connection)? distance?
- Is the atmosphere an obstacle for optical communication, for satellite-Earth link or for two satellites with a big distance so the beam must go through atmosphere?