A Parity-Time-Symmetric Optoelectronic Oscillator Based on Dual-Wavelength Carriers in a Single Spatial Optoelectronic Loop

We theoretically study and experimentally demonstrate a parity-time (PT) symmetric optoelectronic oscillator (OEO) based on dual-wavelength carriers in a single loop configuration. Different from a dual-spatial-loop OEO structure, we use wavelength division multiplexing technology to couple two light waves with different wavelengths into the same a single feedback loop, resulting in two coupled OEO loops in the wavelength domain. The mode selection mechanism of the PT-symmetric system is achieved by adjusting the optical power contrast of the two optical carriers in the feedback loop. A microwave signal with a frequency of 10 GHz is generated with a phase noise of 129.3 dBc/Hz at 10-kHz offset frequency and a sidemode suppression ratio of 66.22 dB. Compared with a PT- symmetric OEO based on two spatially coupled OEO loops, the OEO we propose only involves a single spatial loop structure. It features a single-mode oscillation with a simpler configuration, a more stable oscillation and less vulnerable to the environmental interference, which are critical for some airborne or warfare applications.