Fig. 1. Schematic diagram of open-loop synchronization of optical PPM slots based on FFT

Fig. 2. Frequency estimation errors of different algorithms

Fig. 3. BER of different algorithms. (a) γ˙=5×10^-6, τ˙=-T_c; (b) γ˙=15×10^-6, τ˙=-1.1T_c; (c) γ˙=40×10^-6, τ˙=-1.7T_c; (d) γ˙=24×10^-6, τ˙=-0.2T_c

Fig. 4. BER of different schemes. (a) γ˙=5×10^-6, τ˙=-T_c; (b) γ˙=15×10^-6, τ˙=-1.1T_c; (c) γ˙=40×10^-6, τ˙=-1.7T_c; (d) γ˙=24×10^-6, τ˙=-0.2T_c

Fig. 5. Waveform diagram of the photon. (a) Photon waveform output by MPPC; (b) standard single-photon impulse response

Fig. 6. Schematic diagram of signal recovery. (a) Actual signals; (b) standard single-photon impulse response

Fig. 7. Optical PPM communication system model based on MPPC

Fig. 8. Recovery result of the photon number. (a) Statistical chart of the photon number; (b) comparison chart of the photon number

Fig. 9. BER of the recovery algorithm under different sampling rates

Fig. 10. BER of different algorithms under experimental data. (a) Experiment1; (b) experiment2