Parity-time symmetric coupled optoelectronic oscillator using a polarization-dependent spatial structure

We propose and experimentally investigate a parity-time (PT) symmetric coupled optoelectronic oscillator (COEO) based on a polarization-dependent spatial structure. In such a COEO system, the gain/loss and coupling coefficients of two orthogonal-polarization optical waves can be controlled by adjusting the polarization controller (PC) and the bias voltage of the Mach-Zehnder Modulator (MZM). The single-mode selection can be implemented by the PT symmetry breaking of a special mode. The performance of the proposed COEO is experimentally examined, and a 10.0 GHz microwave signal with a phase noise of −109.1 dBc/Hz @10 kHz and a side mode suppression ratio of 51.4 dB is generated.