Fig. 1. Vortex optical multiplexing communication system based on BP blind equalization algorithm in ocean turbulence channel

Fig. 2. Structure diagram of BP neural network

Fig. 3. Constellation diagram of system received signal. (a) Without BP blind equalization algorithm; (b) after using BP blind equalization algorithm

Fig. 4. Variation curve of system mean square error (MSE) with iteration step using BP blind equalization algorithm

Fig. 5. Variation trend of system BER with SNR under different turbulence intensities

Fig. 6. Variation trend of system BER with SNR under different transmission distances and temperature salinity gradient rates

Fig. 7. BER diagram of system before and after equalization when transmission distance and temperature salinity gradient rate are different

Fig. 8. Variation trend of BER with SNR of different OAM multiplexing state sets under medium turbulence intensity