Optimizing 20 Gbps of ground-to-satellite free-space optical communication in low earth orbit with hybrid wavelength-mode division multiplexing

High-speed free-space optical (FSO) communication has emerged as a promising technology for low earth orbit (LEO) region in the last decade. In this paper, we simulate 20 Gbps simplex ground-to-satellite with various wavelengths and transmitter beam pointing error of 0.1 to 2.5 urad. The C-band wavelength is chosen, and a non-return-zero (NRZ) pulse generator with 16 channels hybrid wavelength-mode division multiplexing (WDM-MDM) technique employing Hermite-Gaussian (HG) modes is used to vary the pointing error. The effect of beam pointing error and receiver aperture diameter was discussed in this paper. A transmitter beam pointing error of 2.5 urad can work appropriately at distances of 1000 km and 1500 km, with a BER value of 1.41 x 10-6 and 3.56 x 10-5, respectively. Based on the receiver aperture diameter of 100 cm, it successfully achieves a BER value of 2.4 x 10-8 at the LEO region and a clear eye diagram.