Fig. 1. Diagram of OFDM-OAM-FSO system. (a) System structure; (b) forked grating; (c) distorted spiral phase

Fig. 2. Processing of OFDM. (a) Generation of OFDM at transmitter; (b) processing of OFDM at receiver

Fig. 3. Turbo code/decode processing. (a) Structure of Turbo coder; (b) structure of Turbo decoder

Fig. 4. Phase diagrams and corresponding demodulated intensity diagrams based on non-Kolmogorov turbulence model with different α. (a)(c)(e) Distorted spiral phase diagrams for Cn2=3×10-13, Cn2=4.5×10-14, Cn2=5×10-15; (b)(d)(f) demodulated intensity diagrams corresponding to Figs. 4(a)(c)(e)

Fig. 5. Received power as a function of Cn2

Fig. 6. Received power as a function of α. (a) Received power for different Cn2; (b) received power for different OAM modes

Fig. 7. Bit error rates in different turbulence conditions. (a) Error rate as a function of Cn2; (b) error rate as a function of α

Fig. 8. Constellations of received signal when α=3.8. (a) Cn2=3×10-13; (b) Cn2=4.5×10-14; (c) Cn2=5×10-15

Fig. 9. Error rates under different received powers when α=3.8. (a) Error rates for different Cn2; (b) error rates with or without channel coding when Cn2=5×10-15

Fig. 10. Bit error rates with or without channel coding. (a) Error rates for different Cn2; (b) error rates for different α