Ship-to-Shore FSO
Under a Phase II SBIR program sponsored by NAVSEA, LSA has developed a Free Space Optical Ship to Shore Communication System to address development of a Low Probability of Intercept/ Detection (LPI/LPD) communication capability for the littoral environment.
Concept Illustration of the Ship-to-Shore FSO point-to-multipoint mesh topology
An FSO system was desired for this application because current tactical radio frequency (RF) communications can be detected and exploited by the enemy. When operating in the world's littorals, Naval forces are inherently vulnerable due to lack of ship maneuverability close to shore, the nature of the operations in which they engage (including amphibious landings), and the high volume of communications and data that must be exchanged among involved units and individuals. Currently, most tactical communications utilize the RF spectrum because it is omnidirectional and the technology is mature. Radio offers adequate bandwidth for voice communications (which can be encrypted to ensure privacy), but typically not enough for situational awareness displays and high-resolution imagery. The tactical weakness of RF for military communications is that it provides an opportunity for opposing forces to detect, intercept, exploit, or target our forces using direction finding or homing systems. Unfortunately, detection of radio transmissions is quite easy because modern scanners have both wide frequency band coverage and rapid scan rates. Clearly, any stealthy activity could be compromised by RF usage, and unencrypted transmissions are easy to exploit. Finally, and most dangerous to our forces, missiles and bombs can (and are) programmed to home on RF transmissions.
Through the SBIR program, LSA and NAVSEA embarked on the analyzing and developing of LPI/LPD communication system envisioned to operate in a hybrid point-to-multipoint topology as depicted in concept graphic. In this type of network, there is a master node capable of supporting a large number of independent links. Each node that it is connected to may be an individual connection, with a single two-way link, or it may be capable of supporting several connections of its own. This type of network permits robust operation, similar in flexibility to an intranet with a central server and peripheral hubs, by providing an efficient hierarchy for the dissemination of data. Ideally, as links becomes unavailable, or new nodes enter the scene, the ad hoc network will automatically recognize their presence or absence and update the network accordingly.
Free Space Optical Hardware developed to demonstrate autonomous acquisition and non-line of sight 100Mbps data transmission.
On the SBIR program, LSA has designed and fabricated five prototype autonomous transceiver nodes that can each autonomously determine their geospatial location and establish a link with another transceiver. Each transceiver node has a 100-Mbps Fast Ethernet communication channel, a 1-km link range, 1550-nm wavelength, eye-safe-at-the-aperture operation, an optical tracking system that has a 10-degree FOV, 200-Hz update rate, and a pointing system that has a 0.015-degree accuracy and 60-degree-per-second tracking speed capability. The five transceivers (pictured above) have been configured into two individual nodes and one master node to allow an "around-the-corner" non-line-of-sight link using FSO communications.
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