Fig. 1. Experimental setup for wide tuning OEO based on direct modulation optical signal injected into semiconductor laser

Fig. 2. Working principle of wide tuning OEO based on direct modulation optical signal injected into semiconductor laser

Fig. 3. Optical spectrum of single frequency optical signal injected into semiconductor laser

Fig. 4. Frequency spectra and phase noise when frequency of OEO output microwave signal is 15.49 GHz. (a) Center frequency;

Fig. 5. Variation of frequency spectra and phase noise of output microwave signal when OEO is tuned. (a) Variation of center frequency; (b) variation of phase noise; (c) summary of data in Figs. 5 (a) and 5 (b)

Fig. 6. Frequency response of master laser

Fig. 7. Variation of frequency and phase noise of output microwave signal when OEO is tuned

Fig. 8. Phase noise of microwave signal from OEO under different structures

Fig. 9. Side mode suppression ratios of output signals from OEO under different structures. (a) Single-ring fiber with length of 2.9 km; (b) single-ring fiber with length of 1.1 km; (c) double-ring fiber consisted of fiber with length of 1.1 km and fiber with length of 2.9 km