Fig. 1. Principle diagram of quantum private communication based on wavelength-mode division co-multiplexing

Fig. 2. Principle diagram of QKD based on double unbalanced M-Z interferometers

Fig. 3. Simulation models of (a) transmitter and (b) receiver of QKD

Fig. 4. Simulation models of (a) transmitter and (b) receiver of classical data

Fig. 5. Structural diagram of quantum private communication system based on wavelength-mode division co-multiplexing

Fig. 6. Frequency spectra of (a) quantum signal and (b) classical optical signal

Fig. 7. Mode field energy distributions of (a) quantum signal and (b) classical optical signal

Fig. 8. Time domain waveforms in (a) D1 and (b) D2 when Δφ=0

Fig. 9. Time domain waveforms in (a) D1 and (b) D2 when Δφ=π

Fig. 10. Time domain waveforms in (a) D1 and (b) D2 when Δφ is π/2 or 3π/2

Fig. 11. Waveforms of classical signals (a) before and (b) after transmission

Fig. 12. Eye diagram of classical light signals