Fig. 1. Block diagram of proposed RF-Pilot phase noise compensation algorithm in combination with EKF

Fig. 2. BER versus OSNR using TD-RF-EKF and EKF-LIPL methods. (a) Linewidth is 1 MHz; (b) under rectangular-16QAM modulation; (c) under rectangular-32QAM modulation

Fig. 3. BER versus laser linewidth using TD-RF and TD-RF-EKF methods under different QAMs. (a) rectangular and circle, 16QAM; (b) rectangular and circle, 32QAM

Fig. 4. Signal constellation diagrams at receiver for rectangular 32QAM when linewidth is 0.9 MHz. (a) Constellation diagram without compensation; (b) constellation diagram after compensation through TD-RF algorithm, in which BER is 3.0×10-2; (c) constellation diagram after compensation through TD-RF-EKF algorithm, in which BER is 3.2×10-3

Fig. 5. Signal constellation diagrams at receiver for circular 32QAM. (a) Constellation diagram after compensation through TD-RF algorithm, in which BER is 2.1×10-2; (b) constellation diagram after compensation through TD-RF-EKF algorithm, in which BER is 3.5×10-3