Self-ILPLL Using Optical Feedback for Phase Noise Reduction in Microwave Oscillators

A novel technique-self-injection-locked and phase-locked loop-using an optical feedback is proposed for phase noise reduction in microwave oscillators. Phase noise reduction of 13 dB at 10-kHz offset has been demonstrated by applying this technique to a 10-GHz dielectric resonator oscillator, achieving -125 dBc/Hz at 10-kHz offset. Phase noise modeling of the feedback technique is also presented, and corroborates with experimental results. Analysis using the modeling has shown that the current limit of the phase noise is due to the system residual noise. Phase noise of -145 dBc/Hz at 10-kHz offset is predicted when the relative intensity noise level is reduced to -170 dB/Hz and the detected photocurrent is increased to 10 mA.