<title>Laser communications for UAV applications</title>

Abstract

Laser communications between high flying aircraft such as high altitude unmanned aerial vehicles offers the potential to transfer extremely high amounts of information faster and with a much smaller package than is possible using current radio frequency and microwave technologies. This can be especially important in transferring time sensitive reconnaissance information because the value of the data can deteriorate rapidly with time. BMDO has funded a number of technology efforts through the U.S. Army Space and Strategic Defense Command reducing the risks associated with laser communications. One of these efforts, at ThermoTrex Corporation in San Diego, California, is now being carried forward towards an advanced technology demonstration. The program leads to the demonstration of high data rate communications of 270 MBPS (mega bits per second) to 1.2 GBPS (giga bits per second) between high altitude aircraft and between a satellite and the ground. The laser communications terminals incorporate atomic line filter technology for background light rejection during acquisition, reactionless Roto-Lok offset cable drive gimbals for fast slewing and high accuracy pointing, and direct digital modulation of semiconductor diode lasers detected with low noise avalanche photodiodes. We present results of a 42 km, 1.2 GBPS laser communications demonstration performed at NASA/JPL Table Mountain facility in Wrightwood, Calif., a 10 km, 1.2 GBPS laser communications demonstration at NRAD in San Diego, Calif., and preliminary results of a 150 km, 1.2 GBPS laser communications demonstration between the islands of Maui and Hawaii.