LDPC-coded OAM based FSO transmission system in the presence of strong atmospheric turbulence

In this invited paper we explore LDPC-coded orbital angular momentum (OAM) based free-space optical (FSO) transmission system in the presence of strong atmospheric turbulence. We find that the BER uncoded curves in the presence of turbulence drop slowly in the regime of high OSNR because of the effect of crosstalk, but when LDPC coding is used, the BER curves drop dramatically with the increase of OSNR. The coding gains is about 3.7, 3.3, and 4.3 dB at BER of 0.04 for OAM states 1, 3, and 5, respectively when single OAM mode is transmitted. In case of OAM multiplexing of states -2, 1, and 4, the curve of OAM state -2 drops along with the increasing OSNR, while error floor can be seen on all the other curves caused by the crosstalk and boundary effect.