Frequency- and Phase-Tunable Optoelectronic Oscillator

An optoelectronic oscillator (OEO) for the generation of a microwave signal with both tunable frequency and phase is proposed and experimentally demonstrated. In the proposed OEO, a single-sideband (SSB) polarization-modulated signal is generated by a polarization modulator (PolM) and a phase-shifted fiber Bragg grating (PS-FBG). The SSB polarization-modulated signal is then split into two parts. One part is sent to a photodetector (PD) and then fed back to the PolM to form the OEO loop. The other part is sent to an electronically tunable polarizer (ETP) and then applied to a second PD. The frequency tunability is achieved by tuning the wavelength of the optical carrier. The tunable phase is introduced by tuning the principal axis of the ETP. An experiment is performed, and a microwave signal with a tunable frequency from 6.6 to 13.1 GHz and a tunable phase from -180° to 180° is generated. The phase noise performance of the generated microwave signal is also evaluated, which is -101.9 dBc/Hz at an offset of 10 kHz.