Fig. 1. Schematic of the PH algorithm

Fig. 2. Schematic of length of summing interval 2i

Fig. 3. Block diagram of the proposed two-stage PH algorithm

Fig. 4. Block diagram of CO-OFDM-PON transmission system based on optical comb

Fig. 5. BER of two algorithms versus different lengths of summing interval 2i

Fig. 6. Signal constellation diagrams and projection histograms obtained by receiver when receiving optical power is -26 dBm. (a) Constellation without phase compensation algorithm; (b) constellation with one-stage PH algorithm (16 test phases); (c) constellation with two-stage PH algorithm (8+8 test phases); (d) projection histogram without phase compensation algorithm; (e) projection histogram with one-stage PH algorithm; (f) projection histogram with two-stage PH algorithm

Fig. 7. (a) BER of the two algorithms versus different number of test phases; (b) BER of five common phase noise compensation algorithms