Layered PAM-DMT for next generation passive optical networks

Layered pulse amplitude modulation with discrete multitone (PAM-DMT) is proposed to improve the system spectral efficiency of existing passive optical networks (PONs) by modulating both the real and imaginary parts of the subcarriers through different layers. Signals from different layers are then combined for simultaneous transmission. At the receiver, an iterative receiver is used to remove the clipping distortion introduced by previous layers. Throughout simulations, we demonstrate enhancement in the receiver sensitivity and the PON reach compared to conventional PAM-DMT when compared at same spectral efficiency. Moreover, the spectral efficiency can be improved by approximately 100% using (log
₂
N - 1) layers compared to conventional PAM-DMT systems, where N is the length of the PAM-DMT sequence.