Parity-time-symmetric optoelectronic oscillator based on normal and reversed traveling-wave modulation

Microwave signal with high frequency and low phase noise is generated based on a parity-time (PT) symmetric optoelectronic oscillator (OEO). The PT-symmetric OEO based on normal and reversed traveling-wave modulation is formed by normal and reversed modulation in a travelling-wave intensity modulator (IM) using the radio-fiber (RF) input and termination ports. Gain and loss balance can be realized to achieve PT symmetry thanks to the different modulation efficiencies for microwave signals applied via different RF ports. The operation of the proposed OEO has been experimentally verified. A microwave signal is generated at 10 GHz with a phase noise of -110.7 dBc/Hz at an offset frequency of 10 kHz and a sideband suppression ratio of 46.46 dB. The approach has potential applications in high-quality microwave signal generation and simplify the structure of PT-symmetric OEO system.