Long-term stable frequency transfer over an urban fiber link using microwave phase stabilization

Area of Science:

• Physics
• Optical Engineering
• Metrology

Background:

• Accurate frequency transfer over long distances is crucial for advanced scientific applications.
• Optical fiber links introduce phase fluctuations that degrade frequency stability.
• Existing methods for frequency stabilization face challenges in real-world environments.

Purpose of the Study:

• To present a novel technique for highly stable frequency comb transfer over long optical fiber links.
• To demonstrate the effectiveness of electronic compensation for mitigating fiber-induced phase noise.
• To validate the technique's performance in both urban and open-air fiber environments.

Main Methods:

• Implementation of an electronic compensation loop to cancel phase fluctuations.
• Utilizing the technique for microwave frequency transfer through a 20 km urban fiber link.
• Testing the technique over an 80 km open-air fiber link.

Main Results:

• Reduced phase fluctuation from 75 mrad to 4 mrad over 48 hours on a 20 km urban link.
• Improved frequency stability by three orders of magnitude on the urban link.
• Reduced root-mean-square phase fluctuation from 580 mrad to 10 mrad over 24 hours on an 80 km open-air link.
• Achieved a two-order-of-magnitude improvement in frequency stability on the open-air link.

Conclusions:

• The novel electronic compensation technique enables highly stable frequency comb transfer over long optical fibers.
• The method effectively cancels phase fluctuations, significantly enhancing frequency stability.
• Demonstrated robustness and effectiveness in diverse long-distance fiber link scenarios.