Laser Stabilization on a Fiber Ring Resonator and Application to RF Filtering

The potential of optical fiber ring resonators for radio frequency (RF) or microwave signals filtering on optical carriers is demonstrated on a short length high Q resonator. The problem of the frequency shift due to the resonator self heating with the optical power is solved thanks to a Pound-Drever feedback loop. A multifrequency RF filter is obtained, with a frequency step of 205 MHz between resonances, and a 3-dB bandwidth of 2.4 MHz. This corresponds to the computed optical resonator 3-dB bandwidth, and thus represents an efficient technique for the measurement of ultrahigh Q optical resonators. In the field of microwave applications, the equivalent Q -factor obtained is particularly interesting in the upper microwave range.