Electronic stabilization methods for a single-loop opto-electronic oscillator

The opto-electronic oscillator (OEO) is an oscillator with an optical delay line as a resonator. The fact that the increase in frequency of an OEO does not increase its phase noise is an important advantage. This enables the generation of low phase-noise signals in the microwave and millimeter wave regions. However, for its more widespread use two problems must be dealt with: frequency drift and multi-mode oscillation. This paper presents recently proposed, novel methods that address the frequency drift and the OEO's multi-mode nature. By implementing a feedback control loop into the OEO it is possible to achieve a frequency drift of 0.05 ppm/K. With an additional phase modulation of the OEO's loop it is possible to increase the side-mode suppression ratio (SMSR) by 5 dB, and a 20-dB improvement in the SMSR is possible with a quality multiplier. The suggested methods operate in the electrical domain, which makes them simple, accessible and low cost.