Fig. 1. Experimental setup for generating tunable broadband MFC

Fig. 2. Experimentally measured power-current curves and relaxation oscillation frequencies as a function of bias current for free-running DFB-SL1 and DFB-SL2，respectively

Fig. 3. Optical spectra（left column）and power spectra（right column）output from DFB-SL1，PM and DFB-SL2. The gray curves in power spectra denote the noise floor，and the resolution bandwidth（RBW）of ESA is 100 kHz

Fig. 4. SSB phase noise curves for f_mod（red curves），13f_mod（blue curves）and 22f_mod（black curves）come lines，and SSB phase noises at 10 kHz frequency offset of representative f_mod，4f_mod，7f_mod，10f_mod，13f_mod，16f_mod，19f_mod and 22f_mod comb lines

Fig. 5. Optical spectra（left column）and power spectra（right column）output from DFB-SL2 with different Δf

Fig. 6. Bandwidth as a function of frequency detuning Δf

Fig. 7. Bandwidth as a function of injection power P_inj

Fig. 8. Power spectra of generated MFCs under different f_mod