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Unidirectional two-way optical frequency comparison and its fundamental limitations.
Optics Letters
|November 2, 2020
Summary
High-quality frequency transfer over urban fiber links enables precise clock comparisons. This study demonstrates a new method for faster, more stable frequency comparisons than satellite links, advancing metrology.
Area of Science:
- Metrology
- Optical Physics
- Telecommunications Engineering
Background:
- High-quality frequency transfer is crucial for comparing advanced microwave and optical clocks.
- Existing telecommunication fiber links offer potential for continental and intercontinental clock comparisons.
Purpose of the Study:
- To present a dataset of unidirectional optical frequency transfer over a 2x43 km urban fiber link.
- To evaluate the performance and limiting factors of this unidirectional frequency transfer method.
- To compare the speed of fiber-based comparisons with satellite links for international primary standards.
Main Methods:
- Collected a half-year-long dataset of unidirectional optical frequency transfer.
- Utilized existing urban telecommunication fiber infrastructure.
- Analyzed frequency instability at various integration times.
Main Results:
- Achieved a relative frequency instability of 8.0x10^-16 at 1 second.
- Reached a best relative frequency instability of 6.0x10^-18 at 10^6 seconds.
- Demonstrated that the unidirectional two-way method enables faster comparisons of international primary standards than satellite links.
Conclusions:
- Unidirectional optical frequency transfer over urban fiber links is a viable method for high-precision clock comparisons.
- The presented method offers a faster alternative to satellite links for comparing international primary standards.
- Identified and investigated the key factors limiting the performance of the unidirectional setup.
