Real-time Downstream 25Gbit/s PAM4 for High Speed TDM-PONs with both 25 and 12.5Gbit/s ONUs

We experimentally achieved 40km, real-time, N1 ODN class (29dB) compliant PAM4 transmission with PAM4/NRZ receptions on the same PON. The emitted PAM4 is interpreted either as PAM4 or NRZ to allow full or half line-rates.