Fig. 1. Block diagram of InGaAs/InP Gm-APD part

Fig. 2. APD single photon detection timing diagram

Fig. 3. The simulation relationship curve of time slot error rate and signal-to-noise ratio under different k values

Fig. 4. PPM modulation flow chart

Fig. 5. PPM modulation simulation diagram

Fig. 6. PPM demodulation flowchart

Fig. 7. PPM demodulation simulation diagram

Fig. 8. Overall block diagram of the communication system

Fig. 9. Physical map of the communication system

Fig. 10. The relationship between PPM synchronization trigger delay time and bit error rate

Fig. 11. Relation curve of gate width and bit error rate

Fig. 12. Dead time and bit error rate relationship curve

Fig. 13. The relationship between received optical power and bit error rate under different code rates

Fig. 14. The relationship between modulation rate and sensitivity under different detection efficiency