Self-Stabilized Optoelectronic Oscillator Using Frequency-Shifted Feedback and a Delay Line

We report a new scheme of photonic microwave oscillator at telecommunication wavelength. It consists of two monolithic distributed feedback (DFB) laser diodes, whose beat-note is stabilized by means of frequency-shifted optical feedback. The feedback beam is modulated by the delayed beat-note itself, and this permits to get a stable optically carried microwave without the need of any external reference. Dual and single sideband modulation schemes were tested by using an intensity modulator and a frequency shifter, respectively. The single sideband scheme results in a better stability and a 10 dB improvement of the phase noise. A phase noise level of -65 dBc/Hz, detection limited, at 100 Hz from a 12 GHz carrier is obtained.