Fig. 1. (a) Schematic diagram of pilot symbol extraction; (b) mean amplitude of each group symbol.

Fig. 2. Schematic diagram of pilot-aided frame synchronization. (a) Obtainment of the PIs between pilot symbols at the same time slot, and variation of PIs with (b) correct and (c) incorrect elimination of modulation information.

Fig. 3. Polarization misaligned frame structure.

Fig. 4. Block diagram of the proposed polarization-joint misaligned pilot-aided carrier recovery scheme. (a) Pilot-aided frame synchronization; (b)–(c) two-stage cascade FOE; (d) phase offset fine estimation; and (e) pilot-aided CPR.

Fig. 5. Schematic diagram of FOE with large PMDs.

Fig. 6. (a) MSE curves with different CFOs for FFT-FOE, pilot-aided polarization-separate FOE (M = 64), and pilot-aided polarization-joint FOE (M = 2, 4, 8). (b) MSE versus DGD.

Fig. 7. BER versus optical signal-to-noise ratio (OSNR) for different carrier recovery schemes.

Fig. 8. Diagram of the experimental setup. RRC, root raised cosine; ECL, external cavity laser; SSMF, standard single-mode fiber; LO, local oscillator.

Fig. 9. BER curves versus ROP with M = 2 when N_b = (a) 64, (b) 128, and (c) 256.

Fig. 10. (a) Spectrum under large CFOs; (b) constellation diagrams of different carrier recovery schemes. BER curves versus ROP when (c) M = 2 and (d) M = 8.