Fig. 1. Simulation setup of 56 GBaud PAM-4 transmission system.

Fig. 2. Contour plots at (a) −4.41  dBm, (b) −5.06  dBm, (c) −5.71  dBm, (d) −6.36  dBm, (e) −7.01  dBm, and (f) −7.66  dBm for 30 GHz. (g) Contour lines at Z = 0 for different ROPs at 30 GHz.

Fig. 3. Contour lines at Z = 0 for different ROPs at (a) 18 GHz, (b) 19 GHz, (c) 20 GHz, and (d) 25 GHz.

Fig. 4. (a) SER versus ROPs at different bandwidths. (b) Contour plot at −5.71  dBm for 18, 19, 20, 25, and 30 GHz. (c) P versus ROPs for 18, 19, 20, 25, and 30 GHz. (d) P versus receiver bandwidths at −4.41, −5.06, −5.71, −6.36, and −7.01  dBm.(e) Comparison among SERC, SERQ, and SERGGD as a function of ROPs at 30 GHz. (f) SER verus P for 18, 19, 20, 25, and 30 GHz at 10 km.

Fig. 5. (a) Eye-diagram and (b) probability distribution function of the received signal of PAM-4 at −7.66  dBm at 30 GHz.

Fig. 6. Experimental setup of 56 Gbaud PAM-4 transmission system.

Fig. 7. Contour lines at Z = 0 for −4, −5, −6, −7. (a) BtB. (b) 10 km. (c) SER versus ROPs for BtB and 10 km. (d) P versus ROPs at BtB and 10 km. (e) SER versus P at BtB and 10 km.

Fig. 8. (a) Eye-diagram and (b) probability distribution function of the received signal of PAM-4 at −7  dBm at 10 km.