Optical RF communications adjunct: Coming of age

The concept of Free Space Optical (FSO) communications has been around since the late 1960's.This paper will describe some recent experimental results that demonstrate and validate hybrid FSO/RF communication links as viable components in a tactical high data rate network. In particular, we will describe air-mountain link closure up to ranges of 200 km under heavy atmospheric turbulence. These links were operated at low packet and bit error rates, with occasional link outages. Like the internet, we used retransmission to minimize the effect of these outages on link throughput. For example, when the FSO system is running, ORCA uses the RF system for retransmission to improve link efficiency. In addition, we will discuss potential losses created by the aircraft aero-optics effects. Finally, we will show comparison between model predictions and experimental data that suggest we can predict link performance if the atmospheric turbulence conditions are known.