A Parity-Time-Symmetric Optoelectronic Oscillator Based on Asymmetrical Electro-Optic Modulation

In this article, a parity-time (PT)-symmetric optoelectronic oscillator (OEO) with a single physical loop is proposed and experimentally demonstrated. In the proposed OEO, the PT symmetry is implemented by constructing two equivalent wavelength-space resonators (WSRs), where the balanced gain and loss are achieved based on asymmetrical phase modulation (PM) to intensity modulation (IM) conversion. By tuning the optical carrier power and/or the optical filtering parameters within the WSRs, a balanced gain and loss status is ensured, thereby enabling single-mode oscillation. The experimental results show the successful generation of a 9.95-GHz microwave signal, exhibiting a high side-mode suppression ratio (SMSR) of 46.94 dB and a low phase noise of −135 dBc/Hz at a 10-kHz offset. In summary, the proposed approach features simple configuration, high spectral purity, and flexible adjustment, providing a new solution for PT-symmetric OEOs.