Fig. 1. Principle of a 45° TFG. (a) Structure of lateral diffraction from the 45° TFG; (b) Divergent output characteristics in radial plane

Fig. 2. Schematic of the proposed dual channel encrypted FSO communication system

Fig. 3. Spectrum of the optical carrier. (a) 1540 nm; (b) 1550 nm

Fig. 4. Temporal waveform of the optical signal. (a) Point A; (b) Point B

Fig. 5. The original RF signals (blue lines) and their reconstruction results with data compression ratios of 16% (red lines) and 8% (green lines) in the 1540 nm temporal domain (a), and the 1540 nm spectral domain (b), and 1550 nm temporal domain (c), and 1550 nm spectral domain (d)

Fig. 6. The input RF signal (a) and its reconstruction results with data compression ratios of 30% (b), 20% (c), and 10% (d) in the temporal domain