Using optical links in space and building high speed laser communications network has proven to be an
extremely complicated task and many such schemes were tried without success in the past. However, in the
last few years, there has been impressive progress made to bring the concept to fruition in civilian and
government-non classified projects. In this paper we will focus on the requirements of the space-based
lasers and optics used for beam forming, as well as receiver antenna gain and detectors used in free space
communications. High data rate, small antenna size, narrow beam divergence, and a narrow field of view are
characteristics of laser communications that offer a number of potential advantages for system design.
Space-based optical communications using satellites in low earth orbit (LEO) and Geo-synchronous orbits
(GEO) hold great promise for the proposed Internet in the Sky network of the future. Also discussed are the
critical parameters in the transmitter, channel, receiver, and link budget that are employed in successful
inter-satellite communications system. We cover that Laser Communications offer a viable alternative to
established RF communications for inter-satellite links and other applications where high performance links
are a necessity.