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

Area of Science:

• Photonics
• Electrical Engineering
• Signal Processing

Background:

• Optoelectronic oscillators (OEOs) are vital for generating stable microwave signals.
• Achieving fine frequency tunability and low drift in OEOs remains a challenge.
• Environmental factors like temperature fluctuations can degrade OEO performance.

Purpose of the Study:

• To propose and demonstrate a finely tunable, low-drift, spurious-free single-loop optoelectronic oscillator (OEO).
• To enhance OEO stability through injection locking and time delay compensation.
• To enable precise frequency control of the OEO output signal.

Main Methods:

• Implementing injection locking of a single-loop OEO mode using a tunable electronic oscillator for single-mode operation.
• Utilizing a time delay compensation system to counteract loop length variations due to environmental changes (temperature, strain).
• Achieving frequency tuning by adjusting the injection frequency and the OEO's absolute loop length.

Main Results:

• Demonstrated a stable single-mode oscillation with a side-mode suppression ratio exceeding 78 dB.
• Achieved a frequency drift of better than -0.1 ppb over a 1000-second period with ambient temperature variations (22°C to 31°C).
• Showcased precise frequency tunability with a step of 10 Hz at an output frequency of 10.664 GHz.

Conclusions:

• The proposed OEO design effectively achieves fine frequency tunability and low drift.
• Injection locking and time delay compensation are critical for robust OEO performance.
• This OEO is suitable for applications requiring highly stable and precisely controlled microwave signals.