Fig. 1. Schematic to generate flat OFC by using cascaded PM and IM

Fig. 2. Waveform of combined fundamental tone and third harmonic that drive the PM

Fig. 3. OFC in simulation, where the PM is driven by combined fundamental tone and third harmonic and the IM is driven by fourth harmonic

Fig. 4. OFC in simulation, where the combined fundamental tone, third and fifth harmonic drive both PM and IM

Fig. 5. Relationship between the flatness of optical frequency comb and the fixed phase of each microwave driving signal under case (b) of Tab. 1

Fig. 6. Modulation indices of all microwave driving signals when the phase of 3-GHz microwave signal that drives PM is fixed under case (b) of Tab. 1

Fig. 7. Modulation indices of all microwave driving signals when the phase of 9-GHz microwave signal that drives PM is fixed under case (b) of Tab. 1

Fig. 8. Modulation indices of all microwave driving signals when the phase of 12-GHz microwave signal that drives IM is fixed under case (b) of Tab.1

Fig. 9. Relationship between the flatness of optical frequency comb and the phase of each microwave driving signal under case (c) of Tab. 1

Fig. 10. Relationship between the flatness of optical frequency comb and the phase of each microwave driving signal under case (a) of Tab.1

Fig. 11. Relationship between the flatness of optical frequency comb and the phase of each microwave driving signal under case (d) of Tab.1

Fig. 12. Relationship between number of comb lines and flatness of the generated OFC

Fig. 13. Experiment setup of the generation for flat optical frequency comb by using cascaded phase modulator and intensity modulator

Fig. 14. OFC in experiment, where the PM is driven by fundamental tone and third harmonic and the IM is driven by fourth harmonic