An Ultra-Low Phase Noise and Highly Stable Optoelectronic Oscillator Utilizing IL-PLL

A new optoelectronic oscillator (OEO) combined with injection-locked (IL) and phase locked loop (PLL) is proposed in this letter. Comparing with a free running OEO, the IL-PLL OEO can suppress the side modes, reduce close-in phase noise, and improve the long-term stability. From the experiment demonstration, a highly stable 9.5-GHz microwave signal with the phase noises of -125 dBc/Hz at 1-kHz offset frequency and -143 dBc/Hz at 10-kHz offset frequency is obtained, and the side-mode suppression ratio is larger than 80 dB and the Allan deviations are 1.37 × 10
^-11
at an average time of 1 s and 1.22 × 10
^-11
at an average time of 1000 s.