Supermode noise suppression with mutual injection locking for coupled optoelectronic oscillator

Area of Science:

• Optoelectronics
• Microwave Engineering
• Signal Processing

Background:

• Coupled optoelectronic oscillators (COEOs) are vital for generating high-frequency, spectrally pure microwave signals.
• A significant challenge in COEOs is the presence of serious sidemode noise, which degrades signal quality.

Purpose of the Study:

• To propose and experimentally validate a straightforward scheme for supermode suppression in COEOs.
• To enhance the spectral purity of microwave signals generated by COEOs.

Main Methods:

• Utilizing mutual injection locking between a multi-mode COEO (master) and a single-mode free-running oscillator (slave).
• Employing a shared electrical feedback path between the master and slave oscillators, avoiding additional hardware complexity.
• Leveraging mode matching and mutual injection locking effects for noise suppression.

Main Results:

• Successfully generated a 9.999 GHz microwave signal with a phase noise of approximately -117 dBc/Hz at a 10 kHz offset frequency.
• Achieved significant supermode noise suppression exceeding 50 dB, reducing noise levels below -120 dBc.
• Demonstrated the effectiveness of the proposed scheme in a practical experimental setup.

Conclusions:

• The proposed mutual injection locking scheme offers a simple and effective solution for supermode suppression in COEOs.
• This technique enhances spectral purity and reduces phase noise without increasing hardware complexity.
• The results pave the way for improved microwave signal generation using COEOs in various applications.