Subcarrier Digital Modulation based Passive Optical Network using clipped signal sending scheme

To economically provide higher bit rate services to users, we previously proposed the Subcarrier Digital Modulation based Passive Optical Network (SDM-PON). We also showed the feasibility of a 16-QAM SDM-PON that constantly provides the service data rate of 1 Gbps to each user, in which ONU biases the QAM signal higher so that it is entirely positive before converting into an optical signal (bias signal sending scheme). To decrease sending optical power, this paper proposes a scheme for clipping negative components of the electrical QAM signal (clipped signal sending scheme), along with three methods for regenerating the original QAM signal at the receiving side. We show that the clipped sending signal scheme, and all three regenerating methods, are effective by simulation. The resulting SDM-PON supports 8 ONUs at different distances, 10 km to 20 km, where each ONU constantly sends 1 Gbps data to OLT using 16-QAM.