Free Space Optical Communication and Network Architecture - Fundamentals, History and Looking Forward

This paper addresses the architecture of free space optical communications and networks (of which satellites are an important modality) from the Physical to the Transport and Application Layers. Optical wireless networks have the potential to serve space-space, space-terrestrial/aircraft, aircraft-aircraft, data centers and metropolitan area networks. Though the technologies in these applications are similar in nature, the architecture constructs and protocol tuning can be very different. Free space optical networks have two attributes that are not encountered in fiber networks and they are: its ability to connect without pre-deployment of infrastructures and to reconfigure its connection topology by beam steering in time scales of ms-s to adapt to traffic loads (as high as 100 Tbps per connection), satellite and mobile platform movements, switching node states and atmospheric conditions. This paper provides a historical perspective on the key development of free space optical communications and presents the research forefront of a multi-layer approach to optical wireless networks and how the network architecture can be tuned to specific applications, concluding with identifying possible novel applications.