Fig. 1. Schematic diagram of FDML OEO, and detuning between period of TBF and loop delay time. (a) Schematic diagram of FDML OEO; (b) detuning between period of TBF and loop delay time

Fig. 2. Experimental device of low phase noise FDML OEO based on ring resonant RF filter

Fig. 3. Effect of half wave bandwidth of RF fast tunable filter on mode-locked matching accuracy of FDML OEO. (a) Measured frequency response S₂₁ of tunable filter with different half-wave bandwidth; (b) phase noise measurement results of DSH beat signal of 50 MHz sweep signal from FDML OEO based on three different half wave bandwidth tunable filters under condition of different mode-locked frequency deviation in Fourier domain

Fig. 4. Phase noise of DSH 4.95 MHz beat frequency signal of 100 MHz frequency sweep signal from FDML OEO based on three different open-loop gains measured at 10 kHz offset under condition of different Fourier domain mode-locked frequency deviation

Fig. 5. Linear frequency sweep signal generated by FDML OEO. (a) Temporal waveform for frequency scanning bandwidth of 400 MHz centered at 9.0 GHz; (b) frequency distribution of short-time Fourier transform; (c) phase noise of DSH signal