Tunable opto-electronic oscillator based on a fiber-ring resonator and a dual-frequency laser

We report on the first tunable opto-electronic oscillator based on a fiber ring resonator and a dual-frequency laser. The dual frequency optical signal is generated by a doubly tunable solid-state dual-frequency laser at telecom wavelength; both optical frequencies are electrically and independently tunable over more than 1 GHz bandwidth. The fiber-ring resonator is 25 meters long and its quality factor is close to 5.10⁸. One laser line is stabilized on a resonance of the resonator with a PDH servo-controller. The heterodyne beatnote, still tunable by adjusting the frequency of the other line, is locked with a so-called optical frequency-locked loop based on the same resonator. As a result, the beatnote is stabilized on the closest multiple of the free spectral range of the resonator. At 10 GHz, we measured a phase noise below -85 dBc/Hz at 10 kHz.