Fig. 1. Block diagram of the proposed PolDemux method based on an AKF.

Fig. 2. Experimental setup and DSP flow of PDM-16QAM systems. (a) The B-to-B case; (b) the 560 km transmission link. ECL: external cavity laser; AWG: arbitrary waveform generator; PC: polarization controller; PBS: polarizing beam splitter; VODL: variable optical delay line; PBC: polarizing beam combiner; EDFA: erbium-doped fiber amplifier; ASE: amplified spontaneous emission; VOA: variable optical attenuator; SMF: single mode fiber; OC: 3 dB optical coupler; OBPF: optical bandpass filter; LO: local oscillator; BPD: balanced photodetector.

Fig. 3. BER performance and required symbol for convergence vs. process noise (Q) in (a) a conventional EKF and (b) the proposed AKF for a PDM-16QAM signal in the B-to-B configuration, for OSNR = 20  dB.

Fig. 4. BER performance vs. the polarization rotation frequency for the PDM-16QAM signal in a B-to-B configuration, for OSNR = 20  dB.

Fig. 5. Comparison of (a) the MSE performance of the modulus of the demultiplexed signal, for OSNR = 20  dB; (b) the B-to-B BER performance.

Fig. 6. Comparison of the B-to-B and 560 km transmission performance for the AKF.

Fig. 7. Polarization tracking stability performance for the proposed method. (a) B-to-B BER performance (OSNR = 20  dB); (b) 560 km transmission BER performance (OSNR = 23 dB).