Power Line Communication (PLC) channel is a fading channel whose their characteristics vary considerably over long distances and at high frequencies, therefore the major challenge, for the researchers, is how to supply robust and efficient communication in PLC systems. To overcome these constraints Cooperative Communication and Network Coding have been demonstrated to be effective techniques. Consequently in this paper, we consider a two-way relaying PLC system in which the Orthogonal Frequency Division Multiplexing (OFDM) is considered for the source 1-to-source 2, the source 1-to-relay and the relay-to-source 2 links where the relay node performs Amplify and Forward (AF) protocol. We propose a conventional bi-directional relaying schema (AF-PLC) which we compare to a schema including a Physical Network Coding (AF-PNC-PLC) for different number of time slots dedicated to exchange data messages between two source nodes S1 and S2 with the assistance of the relay node R. We also evaluate the data rate for OFDM-based two-way relaying AF-PLC and AF-PNC-PLC systems by applying the adaptive modulation technique.