Frequency tunable optoelectronic oscillator with parity-time symmetry by using integrated components

This study introduces a parity-time (PT) symmetric, frequency-tunable optoelectronic oscillator (OEO) using integrated components within a dual-polarization Sagnac loop (SL). By leveraging the natural birefringence of a Z-cut lithium niobate (LiNbO 3 ) phase modulator, interconnected optoelectronic loops with orthogonally polarized light waves are established—one experiencing gain and the other loss. Fine-tuning the polarization states through multiple polarization controllers (PCs) enables precise control over the gain and loss coefficients, achieving the PT symmetry breaking condition necessary to generate a stable, single-frequency microwave signal. The integrated components––the phase modulator (PM), the SL, and the photodetector (PD)––function as a microwave photonic filter (MPF). A tunable laser source combined with a microheater-tuned microdisk resonator (MDR) allows precise frequency adjustments, enabling tunable microwave frequencies from 2 to 12 GHz without additional filters. This integrated approach simplifies the system, reduces its footprint, and enhances the stability against environmental factors. Simulation results demonstrate that the proposed OEO design generates a stable, frequency-tunable microwave signal, achieving single-mode oscillation at 11.8 GHz with a phase noise of −122.5dBc/Hz at a 10 kHz offset frequency.