Fig. 1. Flow chart of K-means clustering algorithm

Fig. 2. Schematic diagram of phase recovery algorithm

Fig. 3. Schematic diagram of system simulation

Fig. 4. Variation of normalized conversion factor with modulus variance

Fig. 5. Radius relocation results. (a) Information entropy is 3.78 bit·symbol^-1; (b) information entropy is 3.56 bit·symbol^-1; (c) information entropy is 3.30 bit·symbol^-1

Fig. 6. BER and EVM after signal recovery under different OSNR. (a) BER; (b) EVM

Fig. 7. NGMI curves of 16QAM with different information entropy and different line width

Fig. 8. BER and EVM after signal recovery under different OSNR. (a) BER; (b) EVM

Fig. 9. NGMI curves of 64QAM with different information entropy for different line width

Fig. 10. Simulation results. (a)(b) 4 bit·symbol^-1 16QAM; (c)(d) 2.8 bit·symbol^-1 16QAM; (e)(f) 6 bit·symbol^-1 64QAM; (g)(h) 4.71 bit·symbol^-1 64QAM