An Orbital Angular Momentum (OAM) based LDPC-coded modulation scheme suitable for use in FSO communication is proposed. They demonstrate that the proposed scheme can operate under strong atmospheric turbulence regime and enable 100 Gb/s optical transmission while employing 10 Gb/s components.
Both binary and nonbinary LDPC-coded OAM modulations are studied. In addition to providing better BER performance, the nonbinary LDPC-coded modulation reduces overall decoder complexity and latency. The nonbinary LDPC-coded OAM modulation provides a net coding gain of 9.3 dB at the BER of 10-8. The maximum-ratio combining scheme outperforms the corresponding equal-gain combining scheme by almost 2.