Tunable low-drift spurious-free optoelectronic oscillator based on injection locking and time delay compensation

A finely tunable low-drift spurious-free single-loop optoelectronic oscillator (OEO) incorporating injection locking and time delay compensation is proposed and experimentally demonstrated. In the proposed OEO, one mode of a single-loop OEO is injection locked by a tunable electronic oscillator resulting in single-mode oscillation. A time delay compensation system is used to compensate the OEO’s loop length change caused by environmental changes, such as temperature and strain. Tuning of the oscillation frequency is realized by controlling the injection frequency and absolute loop length of the single-loop OEO. In the experiments, when the ambient temperature varies between 22°C and 31°C within 1000 s, an output signal at the frequency of 10.664 GHz with a frequency drift better than −0.1  ppb and side-mode suppression ratio greater than 78 dB has been realized. Also, the OEO can be tuned with a precise frequency step of 10 Hz.