Inter-satellite optical communication networks: RF fading diversity for higher spectral efficiency

Revolutionary developments in semiconductors lead to efficient deployment of lasers and photodetectors, thus enabling optical transmission of data signals, whether in fiber optic links or free space. Line of sight transmission characteristic of optics ensures the security of the data. With the incessant increase in the numbers of satellites and the data payload required to handle, it is inevitable that in the future we will see a shift towards optical networking, especially in the earth orbiting satellites. We demonstrate a novel all-optical multiplexing technique for doubling the usable spectral bandwidth and number of channels in subcarrier-modulated data transmission over free-space optical connections. By taking advantage of the chromatic-dispersion-induced RF power fading of a given subcarrier frequency, we can transmit two subcarrier channels that occupy the same frequency space.. We successfully transmit and receive two 155 Mbit/s data channels that are both located at 7.1 GHz.