Fig. 1. Schematic of random optoelectronic oscillator with high signal-to-noise ratio

Fig. 2. Experimental device of random optoelectronic oscillator with high signal-to-noise ratio

Fig. 3. Random microwave signal generated by a random optoelectronic oscillator. (a) 0-30 GHz random signal, including oscillating OEO signal and open-loop substrate noise; (b) 200 μs time-domain spectrum of oscilloscope random signal with sampling rate of 4 GSa/s; (c) time-domain waveform of random signal with time width of 0.56 ps; (d) simulation of autocorrelation function of time-domain waveform

Fig. 4. OEO spectrum and open-loop spectrum. (a) Spectrum measured by OSA1; (b) spectrum measured by OSA2

Fig. 5. Effect of WDM2 on SNR of random microwave signals. (a) Using WDM2, SNR of random microwave signal reaches 40 dB; (b) without WDM2, SNR of the random microwave signal is in the range of 20 dB to 30 dB

Fig. 6. Effect of WDM2 on optical spectrum. (a) Open-loop condition; (b) OEO condition

Fig. 7. Effect of WDM2 on signal power. (a) Random microwave signal of OEO without WDM2; (b) random microwave signal of OEO with WDM2

Fig. 8. Effect of different Raman pumping power on the power of random microwave signal