Long-Term Frequency Stabilization of an Optoelectronic Oscillator Using Phase-Locked Loop

We demonstrate an approach of long-term frequency stabilization of a single-loop optoelectronic oscillator (OEO) with a phase-locked loop (PLL). The OEO is frequency locked to a highly stable microwave reference via a PLL circuit with a PID regulator. With this approach, we obtained a highly stable 3.035-GHz microwave signal with phase noise of -65 dBC/Hz at 10-Hz offset frequency, and the frequency stability has reached 6.98 × 10^-14 at average time of 1000 s. These experimental results show that the PLL-locked OEO is greatly improved in both long-term frequency stability and phase noise performance at low offset frequencies. Therefore, the PLL-locked OEO can be a strong candidate of highly stable, low phase noise microwave generators for microwave photonics applications.