Fig. 1. Timing synchronization structure based on guard time with sampling frequency of 1 slot

Fig. 2. Schematic diagram of timing error with sampling frequency of 1 slot

Fig. 3. Statistical diagram of photon counts. (a) Synchronization; (b) non-synchronization

Fig. 4. Distribution curves of statistical photon counts (σ=0.2, τ₀=1.2, γ=50, P=3, M=16, K_s=2, K_b=0.2)

Fig. 5. Fitting diagram of the distribution curves of photon counts

Fig. 6. Timing diagram of signal sampling point and interpolation adjustment point

Fig. 7. Statistics of frequency offset estimation errors under different number of guard time and different statistical data amounts. (a) P=3, N=4×2520; (b) P=2, N=4×2520; (c) P=1, N=4×2520; (d) P=3, N=2×2520; (e) P=3, N=1×2520

Fig. 8. Statistics of estimated initial phase errors under different number of guard time and different statistical data amounts. (a) P=3, N=4×2520; (b) P=1, N=4×2520; (c) P=3, N=1×2520

Fig. 9. Interpolation matching search fine synchronization scheme based on guard time

Fig. 10. Statistical photon count distribution of different frequency offset errors (M=16, P=3, N=2520, K_s=2, K_b=0.2, (τ₀)_f=0.2 slot, Δγ=-1.8, σ=0.2)

Fig. 11. Statistical photon count distribution of different initial phase fractional offset (M=16, P=3, N=2520, K_s=2, K_b=0.2, (τ₀)_f=0.2 slot, Δγ=-1.8, σ=0.2)

Fig. 12. Comparison of bit error performance of different methods (N=2520, P=3, K_b=0.2, σ=0.2)

Fig. 13. Bit error performance of different statistics (N=2520, K_b=0.2, σ=0.2)

Fig. 14. Bit error performance of different jitter parameters (K_b=0.2, σ=0.2, P=1)

Fig. 15. Bit error performance under different guard time (N=2520, P=3, K_b=0.2)