Transmitter diversity based on phase-division

Abstract

Current satellite communication systems based on RF technology are often limited by the available spectrum. Free-Space Optical Communication Links are a promising solution to overcome this bottleneck. The available spectrum enables Terabit-per-Second data rates, and the point-to-point nature of FSO links makes spectrum regulation unnecessary. Therefore, the use of optical links is investigated in a number of scenarios, as e.g. for GEO feeder links serving multimedia applications. Transmitter Diversity might be a solution to overcome atmospheric impacts on the ground-to-satellite transmission in an optical GEO feeder link application. Transmitter Diversity can e.g. be implemented by using various spectral channels. Despite the virtually unlimited bandwidth available in atmospheric transmission windows, practical implementations of an optical GEO feeder link need to use available hardware, namely fiber amplifiers in the C- and L-band – Therefore, a more efficient use of the available spectrum will enable in a higher system throughput. In this paper, we present a bandwidth efficient transmitter diversity scheme, called phase-division in bit-time. It is based on Intensity Modulation with Direction Detection, and makes use of phase modulation for the transmitters to mitigate the impact of atmospheric phase distortions on the quality of the received signal.