Improvement in the Phase Noise of a 10 GHz Optoelectronic Oscillator Using All-Photonic Gain

We have investigated the improvement in the phase noise of a 10 GHz optoelectronic oscillator using all-photonic gain as compared to using an electronic amplifier in the cavity. The optoelectronic oscillator achieves the necessary RF gain for oscillation by using the carrier-suppression technique of a low-biased Mach-Zehnder modulator (MZM) followed by optical amplification. The measured RF gain due to this all-photonic technique is as high as 15 dB and matches well with theoretical predictions. The phase noise of the generated 10 GHz signal is at least 10 dB lower than the signal from the same oscillator using an electronic amplifier. The improvement in the phase noise is due to the lower RF noise figure of the all-photonic gain process as compared to the electronic amplifier configuration.