For the first time, we propose and demonstrate a novel three-level Signal allocation scheme OFDM PON architecture which makes the best use of OFDM characteristics. In the architecture, we produce five-carrier signal optically by MZM, use odd carriers modulating downlink data and retain even carriers for uplink data. Multiple signal distribution methods can be switched flexibly. By simulation, a small PON systems with four ONU based on this architecture was realized. Both the downlink and uplink transmission adopt 4-QAM-OFDM signal. The transmission rate will be demonstrated to exceed 10Gbit/s.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.