Unique properties of solar blind ultraviolet communication systems for unattended ground-sensor networks

摘要

Solar blind ultraviolet communication systems can provide short to medium range non line-of-sight and line-of-sight links which are covert and insensitive to meteorological conditions. Operation in the solar blind region provides zero background conditions and strong scattering interactions. Scattering provides the basis for transferring information when non line-of-sight conditions exist. Zero background conditions are a result of strong absorption of solar radiation in the upper atmosphere. These conditions make it possible to operate very sensitive wide field-of-view quantum noise limited photon counting receivers, and provide communication systems that perform very differently than free space optical systems that operate in other spectral regions. These systems may be compact and require very low primary power for operation. Non line-of-sight ultraviolet communication systems can provide reliable inter-nodal communications for unattended ground sensor networks. This type of system is particularly attractive when non line-of-sight conditions exist between nodes, covert operation is required, and insensitivity to positioning and ground proximity are desired. Light emitting diode technology being developed under the DARPA SUVOS program represents an enabling technology for these systems. Small, low power and low cost systems compatible with unattended ground sensor networks will be available as a result of this program. Data rates of hundreds of kbps with bit error rates (BER) of 10-7 and inter-nodal ranges of hundreds of meters are consistent with phenomenology and technology. Line-of-sight ultraviolet communication systems also offer some unique characteristics for exfiltration of data from an unattended ground sensor network. The absence of background radiation makes it possible to operate with wide field-of-view receivers and large transmitter cone angles. This capability significantly reduces acquisition/pointing/tracking requirements that are traditionally associated with free space optical links. In addition, strong forward aerosol scatter in the ultraviolet reduces dependence on meteorological conditions. The operational range of line-of-sight solar blind communication systems is on the order of kilometers. By selection of operating wavelength within the solar blind region, performance can be optimized to provide reliable communications and at the same time provide covert operation. Data rates on the order of megabits per second are possible with line-of-sight systems.