Fig. 1. Experimental setup of underwater optical communication

Fig. 2. Principle of phase map synthesis loaded into SLM. (a) Spiral phase diagram; (b) blazed grating; (c) fork grating

Fig. 3. Beam emerging from SLM

Fig. 4. Spot morphology after vortex wave plate detection. Transmitter emits a vortex beam with topological charge of +3, and the receiver adopts (a) m=-3 and (b) m=+3 vortex wave plate detection; transmitter emits a vortex beam with topological charge of -3, and the receiver adopts (c) m=-3 and (d) m=+3 vortex wave plate detection

Fig. 5. FPGA information processing process

Fig. 6. Topological charge crosstalk of vortex beams in experimental system

Fig. 7. Crosstalk rate between two channels of the experimental system

Fig. 8. Signal-to-noise ratio between two channels of the experimental system

Fig. 9. Bit error rate of communication experiment