Optical OTFS Modulation for Free Space Optical-Based LEO Satellite Communication Systems

To further enhance the link stability of laser satellite communication (SatCom) systems, a direct current-biased optical orthogonal time-frequency-space (DCO-OTFS) modulation is proposed for free-space optical (FSO)-based SatCom. The proposed pilot-assisted DCO-OTFS can preserve the orthogonality in the delay-Doppler channel and achieve cost-effective signal compensation, thus alleviating the impact of fading effects in SatCom. In a 100 Gbps satellite-to-ground simulation, the OTFS-based system is developed and evaluated against traditional systems under various conditions. Simulation results demonstrate that the OTFS-based system achieves a power gain of 6 dB and exhibits robust resistance to pointing jitter. Moreover, with equivalent launch power, the OTFS-based system can reduce the receiver aperture diameter by 35% while maintaining comparable bit error rate performance.