Fig. 1. Constellation comparison before and after Cir-MQAM geometric shaping (GS). (a) Constellations of Cir-8QAM and GS-Cir-8QAM; (b) constellations of Cir-16QAM and GS-Cir-16QAM; (c) constellations of Cir-32QAM and GS-Cir-32QAM

Fig. 2. Probability distribution of PS-GS-Cir-MQAM. (a) Probability distribution of PS-GS-Cir-8QAM; (b) probability distribution of PS-GS-Cir-16QAM; (c) probability distribution of PS-GS-Cir-32QAM

Fig. 3. Constellation distributions of PS-GS-Cir-MQAM. (a) Constellation distribution of PS-GS-Cir-8QAM; (b) constellation distribution of PS-GS-Cir-16QAM; (c) constellation distribution of PS-GS-Cir-32QAM

Fig. 4. Vector THz signal generation system based on geometric probability hybrid shaping

Fig. 5. Bit error rate (BER) curves and constellation diagrams of Cir-8QAM, GS-Cir-8QAM, and hybrid shaping 8QAM (input PD power is -10 dBm). (a) PS-GS-Cir-8QAM transmitted over 120 km NLSF; (b) GS-Cir-8QAM transmitted over 120 km NLSF; (c) Cir-8QAM transmitted over 120 km NLSF; (d) BER curves

Fig. 6. BER curves and constellation diagrams of Cir-16QAM, GS-Cir-16QAM, PS-Cir-16QAM, and hybrid shaping Cir-16QAM (input PD power is -11 dBm). (a) PS-GS-Cir-16QAM transmitted over 100 km NLSF; (b) GS-Cir-16QAM transmitted over 100 km NLSF; (c) PS-Cir-16QAM transmitted over 100 km NLSF; (d) Cir-16QAM transmitted over 100 km NLSF; (e) BER curves

Fig. 7. BER curves and constellation diagrams Cir-32QAM, GS-Cir-32QAM, PS-Cir-32QAM, and hybrid shaping Cir-32QAM (input PD power is -9 dBm). (a) PS-GS-Cir-32QAM transmitted over 70 km NLSF; (b) PS-Cir-32QAM transmitted over 70 km NLSF; (c) GS-Cir-32QAM transmitted over 70 km NLSF; (d) Cir-32QAM transmitted over 70 km NLSF; (e) BER curves