Fig. 1. Schematic diagram of signal timing in OOK, DPPM and PPM formats

Fig. 2. Signal transmission system of IMDD in simulation

Fig. 3. ROP performance of transmitting DPPM signal in IMDD system

Fig. 4. Coherent optical transmission system under simulation condition

Fig. 5. ROP performance of DPPM signals with different rates in coherent optical transmission system

Fig. 6. Simulation performance of DPPM signals with different power with respect to intrinsic optical power

Fig. 7. The structure of coherent optical transmission

Fig. 8. Live picture of traditional coherent optical transmission platform

Fig. 9. Experimental performance of optical power at receiving end under different rates of DPPM signals

Fig. 10. Experimental performance of DPPM signals with different rates on optical fiber length