Optoelectronic Oscillator Using an Ultra-High Finesse Fabry-Perot Etalon as a Photonic Filter for Low Phase Noise at High Oscillating Frequencies

A 100,000 finesse Fabry-Perot etalon with a 1.5 GHz free spectral range is used as a photonic filter in an optoelectorinc oscillator. The etalon acts as a similar to 15 kHz microwave filter to suppress spurious modes in a single loop OEO configuration. The etalon maintains its narrow filtering capability at harmonics of the FSR. Phase noise of the 10.5 GHz tone with 2 km of delay is measured at -120 dBc/Hz at 10 kHz offset. Oscillation as high as 54 GHz with 3 km of fiber delay is achieved while maintaining suppression of spurious modes below the noise floor of the measurement. Pound-Drever-Hall frequency stabilization of the laser frequency is used to reduce optical frequency noise and keep the laser frequency centered within the etalon resonance for long term operation of the OEO.