Frequency comb-based microwave transfer over fiber with 7×10(-19) instability using fiber-loop optical-microwave...

Area of Science:

• Physics
• Optical Engineering
• Metrology

Background:

• Accurate transfer of microwave/radio frequency (RF) signals over long distances is crucial for applications like distributed timing systems and fundamental physics experiments.
• Fiber optic links are susceptible to phase fluctuations, which degrade the precision of transferred RF signals.
• Existing methods often require complex dispersion compensation and have limitations in stability and resolution.

Purpose of the Study:

• To demonstrate a novel remote microwave/RF transfer technique.
• To stabilize a fiber link for high-precision RF signal transmission.
• To achieve sub-femtosecond resolution and long-term stability in remote RF signal transfer.

Main Methods:

• Utilized a fiber-loop optical-microwave phase detector (FLOM-PD) for link stabilization.
• Employed direct phase comparison between a remote optical pulse train and a local microwave/RF signal.
• Implemented a technique to compensate for excess phase fluctuations in the fiber link.

Main Results:

• Achieved sub-femtosecond resolution for remote RF signal transfer.
• Demonstrated long-term stable link stabilization over a 2.3 km fiber link.
• Attained fractional frequency instability of 7.6×10(-18) at 1000 s and 6.5×10(-19) at 82,500 s for 2.856 GHz RF oscillators.
• Showcased a wide timing detection range with reduced demand for fiber dispersion compensation.

Conclusions:

• The developed FLOM-PD based technique effectively stabilizes fiber links for remote RF transfer.
• The method offers superior resolution and long-term stability compared to existing techniques.
• This advancement has significant implications for distributed timing, metrology, and scientific research requiring precise RF signal synchronization.