Fig. 1. The roadmap for ITU-T standards of PON

Fig. 2. Deployed ONU architecture and grouping scheme diagram

Fig. 3. Flexible rate adjustment based on coding and modulation

Fig. 4. Schematic diagram of entropy-loading discrete multi-tone technology

Fig. 5. Schematic diagram of hybrid time and frequency domain flexible multiple access architecture

Fig. 6. The ultra-simple coherent transceiver for ONU