COLORADO SPRINGS, Colo. -- Discovery Semiconductor Inc. (Ewing, NJ) has demonstrated 10-Gbit/sec free-space optical links in tests at Kirtland Air Force Base in New Mexico. The tests were performed under the auspices of the Air Force Research Labs' Space Vehicles Directorate, which is considering replacing RF links with FSO in some inter-satellite link designs.
Dr. Christoph Wree, program manager at Discovery, said that the company has experimented with many different modulation schemes, but the Return-to-Zero Differential Phase Shift Keying (RZ-DPSK) modulation used in this test provided the best resilience, particularly within the atmosphere, where scintillation effects must be overcome.
Discovery provided the full transceiver subsystem, operating at 1550 nm. Science Applications International Corp. collaborated in testing the system, and Schafer Corp. partnered in analysis and management services.
The tests, conducted several months ago in New Mexico, showed a receiver sensitivity of 27 photons per bit, and a bit error ratio of 1e-9, a figure only 5 photons away from the quantum limit. Results indicate FSO links could overcome losses either in the long distances in orbital ISL applications, or in atmospheric turbulence in airborne applications.