A 30-GHz Self-Injection-Locked Oscillator Having a Long Optical Delay Line for Phase-Noise Reduction

We demonstrate a millimeter-wave self-injection-locked (SIL) oscillator having a long optical delay line as a feedback route. In the SIL oscillator, a part of output signal is self-injected into the oscillator after passing through a long optical delay line, resulting in locked oscillation and phase-noise reduction. By controlling the self-injection power, we achieve 30-GHz oscillation with a sidemode suppression ratio larger than 50 dB and about 18-dB phase-noise reduction at 10-kHz frequency offset.