Abstract
Due to the rapid growth of high-resolution services, low earth orbit satellite-to-ground (LEO-StG) optical communications are expected to provide higher speed and better receiver sensitivity transmission. Here, we propose a phase uniformly distributed circular m-ary quadrature amplitude modulation (MQAM) combined with probabilistic shaping (PS) scheme for polarization multiplexing coherent optical orthogonal frequency-division multiplexing (PM-CO-OFDM) systems in LEO-StG communications to achieve high capacity transmission and improve receiver sensitivity as well as linewidth tolerance. In such scheme, the radius ratio of the circular 16/32QAM is optimized to maximize the minimum Euclidean distance (MED), and the constellation points of each ring are uniformly distributed to maximize the phase space of adjacent constellation points. Besides, the circular 16/32QAM is combined with probabilistic shaping (PS) to further increase the MED under the constraint of average transmit power. Simulation results of such circular 16/32QAM combined with PS scheme under different turbulence channels not only demonstrate its feasibility, but also show the improvements in receiver sensitivity and linewidth tolerance compared with regular 16/32QAM under same entropy. The improvement of receiver sensitivity is also experimentally validated. The superiorities of such scheme make it highly desirable for potential application in long-reach, non-relay, and high capacity LEO-StG optical communications .
Highlights
With the development of high-resolution services, satellite to ground downlink transmission systems have been requested for transmitting the increasing volume of data to ground stations within the limited satellite visible time [1]
Simulation results of such circular 16/32QAM combined with probabilistic shaping (PS) scheme under different turbulence channels demonstrate its feasibility, and show the improvements in receiver sensitivity and linewidth tolerance compared with regular 16/32QAM under same entropy
We present a novel phase uniformly distributed circular 16/32QAM combined with PS scheme for CO-orthogonal frequency division multiplexing (OFDM) systems in low earth orbit satellite-toground (LEO-StG) optical communications to achieve high capacity transmission and improve the receiver sensitivity as well as linewidth tolerance
Summary
With the development of high-resolution services, satellite to ground downlink transmission systems have been requested for transmitting the increasing volume of data to ground stations within the limited satellite visible time [1]. CO-OFDM using higher-order polarization multiplexing m-ary quadrature amplitude modulation (PM-MQAM) which combines the advantages of high receiver sensitivity, high spectral efficiency and flexibility, is one of potential technology to achieve high capacity optical transmission with high spectral efficiency for LEO-StG communications. We present a novel phase uniformly distributed circular 16/32QAM combined with PS scheme for CO-OFDM systems in LEO-StG optical communications to achieve high capacity transmission and improve the receiver sensitivity as well as linewidth tolerance. At the same time, considering the sensitivity to phase noise in CO-OFDM systems, the constellation points of each ring are uniformly distributed to maximize the phase space of adjacent constellation points Such circular 16/32QAM is combined with PS to further increase the MED under the constrained mean power. The improvement of receiver sensitivity is experimentally validated on 16QAM CO-OFDM systems
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