A Frequency-tunable Two-tone RF Signal Generator by Polarization Multiplexed Optoelectronic Oscillator

A two-tone radio frequency (RF) signal generator realized by a polarization multiplexed optoelectronic oscillator (OEO) is proposed and demonstrated. The OEO employs a dual-polarization modulator and can simultaneously generate two frequency tones through OEO oscillations in two orthogonal polarizations of the same optical carrier. Frequencies of the two tones can be tuned independently by adjusting the electrical filters. Advantage of the proposed system is that, the optical interference between two-tone oscillations is effectively suppressed by polarization isolation and the multi-frequency intermodulation in a single modulator is avoided, which leads to the generation of a high quality two-tone RF signal. In the experiment, a two-tone signal at 9.95GHz and 10.66 GHz is generated with a phase noise (@10kHz) of -105.06 dBc/Hz and -104.43 dBc/Hz, respectively. The frequency tunability of the two-tone signal generator is also demonstrated in a range from 4 GHz to 12 GHz.