O'Reilly logo

Optical Networking Best Practices Handbook by John R. Vacca

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

7.4. SECURE FREE-SPACE OPTICAL COMMUNICATION

It is desirable in certain applications to establish bursty, high-speed, free-space optical links over distances of up to several kilometers between rapidly moving platforms, such as air or ground vehicles, while minimizing the probability that a link is detected or intercepted. In a collaboration between University of California, Berkeley, Stanford University, Princeton University, and Sensors Unlimited, researchers have undertaken work toward this goal [4].

There are several key elements in the researchers' approach to covert optical links. To minimize atmospheric scattering, they used a long transmission wavelength; 1.55 μm was chosen because of the availability of key transmitting and receiving components. Combining a high-power laser and a two-dimensional beam scanner employing micromirrors, researchers obtained a steerable transmitter with milliradian beam width and submillisecond aiming time. They combined a wide-angle lens and InGaAs photodiode array with a dual-mode readout integrated circuit (ROIC) capable of both imaging and high-speed data reception, obtaining an electronically steerable receiver with a wide FOV and angular resolution in the milliradian range [4].

Covertness is defeated most easily during the link acquisition phase, when at least one communicating party must perform a broad-field scan to acquire the position of the other party, and risks revealing their presence to an observer. The researchers adopted a ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required