Fig. 1. Signal generation schemes based on space-to-time mapping and frequency-to-time mapping. (a) Signal generation scheme based on space-to-time mapping^[41]; (b) signal generation scheme based on frequency-to-time mapping^[42]

Fig. 2. Signal generation schemes based on photonic assisted frequency band spread. (a) Signal generation scheme based on MZM^[43]; (b) signal generation scheme based on DPMZM^[44]; (c) signal generation scheme based on OFC^[45]

Fig. 3. Signal generation scheme based on OFC and time-frequency two-dimensional filter^[47]

Fig. 4. Signal generation schemes based on spectrum stitching. (a) Spectrum stitching scheme based on double OFC frequency up-conversion^[48]; (b) spectrum stitching scheme based on single OFC and time-frequency two-dimensional filter^[49]

Fig. 5. Signal generation scheme based on laser operating in period-one (P1) oscillation state^[50]

Fig. 6. Signal generation scheme based on FDML-OEO^[52]

Fig. 7. Signal generation scheme based on laser direct modulation^[56]

Fig. 8. LFM signal generation scheme based on phase-locked synchronous laser source. (a) Schematic of proposed signal generation scheme; (b) spectra at several key points labeled in system; (c) schematic architecture of master and slave lasers

Fig. 9. Output spectra of master and slave lasers

Fig. 10. Experimental structure diagram of laser linewidth measurement

Fig. 11. Frequency noises of master and slave lasers

Fig. 12. Frequency modulation characteristics of master and slave lasers. (a) Continuous frequency modulation output spectra of master laser; (b) frequency response diagram of slave laser

Fig. 13. Frequency spectra and phase noise spectra of beat frequency signal of master and slave lasers in phase-locking and free-running states. (a) Frequency spectra; (b) phase noise spectra

Fig. 14. Temporal waveform, instantaneous frequency-time diagram, and frequency spectrum of generated LFM signal. (a) Temporal waveform; (b) instantaneous frequency-time diagram; (c) frequency spectrum

Fig. 15. Residual frequency errors of LFM signal under free-running and phase-locking states

Fig. 16. Frequency spectra of generated LFM signal covering different frequency bands (from L to Ka)

Fig. 17. Temporal period tuning of generated LFM signal