All-optical microwave signal generation based on a DFB laser self-injection-locked to a fiber Fabry-Perot resonator

We report the all-optical generation of a 10.2 GHz microwave signal based on the self-injection locking of a distributed feedback laser to a fiber Fabry-Perot cavity through a passive optical feedback loop. By adjusting the feedback strength, we show that the system can oscillate on one or several modes of the Fabry-Perot cavity. Mode beating is advantageously exploited to generate an optically carried microwave signal whose frequency is set by the free spectral range of the Fabry-Perot. Depending on the laser current and environmental insulation, our table-top setup provides stable single-frequency microwave generation maintained for more than 30 minutes without mode hopping between the closely spaced external cavity modes supported within each Fabry-Perot resonance. The generated microwave signal exhibits a phase noise of -90 dBc/Hz at 10 kHz offset from the carrier. These results open the way towards the realization of compact photonic microwave signal generation relying purely on optical feedback, without requiring any optoelectronic loop, external modulator, or electrical filter.