Synchronization of clocks through 12 km of strongly turbulent air over a city
Open accessAbstract
We demonstrate real-time, femtosecond-level clock synchronization across a low-lying, strongly turbulent, 12-km horizontal air path by optical two-way time transfer. For this long horizontal free-space path, the integrated turbulence extends well into the strong turbulence regime corresponding to multiple scattering with a Rytov variance up to 7 and with the number of signal interruptions exceeding 100 per second. Nevertheless, optical two-way time transfer is used to synchronize a remote clock to a master clock with femtosecond-level agreement and with a relative time deviation dropping as low as a few hundred attoseconds. Synchronization is shown for a remote clock based on either an optical or microwave oscillator and using either tip-tilt or adaptive-optics free-space optical terminals. The performance is unaltered from optical two-way time transfer in weak turbulence across short links. These results confirm that the two-way reciprocity of the free-space time-of-flight is maintained both under strong turbulence and with the use of adaptive optics. The demonstrated robustness of optical two-way time transfer against strong turbulence and its compatibility with adaptive optics is encouraging for future femtosecond clock synchronization over very long distance ground-to-air free-space paths.
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It is not clear yet if phase coherent free space optical links will be able to be as good as optical fibre techniques, mainly because of atmospheric turbulence.
“It is not clear yet if these techniques will be able to be as good as optical fibre techniques, mainly because of the effect of atmospheric turbulence [114, 115, 116].”
From Chronometric Geodesy: Methods and Applications (2019) · cites this paper as [115]
The passage on turbulence challenges (section labeled Abstract; page not provided) describes timing fluctuations and signal dropouts, supporting atmospheric turbulence as a concern for free-space links. The paper also reports robust femtosecond-level synchronization across a strongly turbulent 12-km path. It does not compare that performance with optical-fibre techniques or say whether the two can ultimately perform equally well. (LLM, conf=0.83)
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Cites
Search for Ultralight Scalar Dark Matter with Atomic Spectroscopy
Van Tilburg, K., Leefer, N., Bougas, L., & Budker, D. (2015) · Physical Review Letters · doi:10.1103/physrevlett.115.011802 · Cited by 253 · see citing works
Quantum tests of the Einstein Equivalence Principle with the STE–QUEST space mission
Altschul, B., Bailey, Q. G., Blanchet, L., Bongs, K., Bouyer, P., Cacciapuoti, L., Capozziello, S., Gaaloul, N., Giulini, D., Hartwig, J., et al. (2015) · Advances in Space Research · doi:10.1016/j.asr.2014.07.014 · Cited by 204 · see citing works
Towards a redefinition of the second based on optical atomic clocks
Riehle, F. (2015) · Comptes Rendus. Physique · doi:10.1016/j.crhy.2015.03.012 · Cited by 174 · see citing works
Robert, C., Conan, J.-M., & Wolf, P. (2016) · Physical Review A · doi:10.1103/physreva.93.033860 · Cited by 84 · see citing works
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Research works printed but not linked: 3
- [3]Chou CW Hume DB Rosenband T Wineland DJ Optical Clocks and Relativity Science 329 1630 2010 20929843
- [7]Cliche J-F Shillue B Precision timing control for radioastronomy: maintaining femtosecond synchronization in the Atacama Large Millimeter Array IEEE Control Syst 26 19 2006
- [13]Bergeron H Sinclair LC Swann WC Nelson CW Deschênes J-D Baumann E Giorgetta FR Coddington I Newbury NR Tight real-time synchronization of a microwave clock to an optical clock across a turbulent air path Optica 3 441 2016 PMC5876866 29607352
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Chronometric Geodesy: Methods and Applications
Delva, P., Denker, H., & Lion, G. (2019) · Fundamental Theories of Physics · doi:10.1007/978-3-030-11500-5_2 · Cited by 28 · see citing works
“cal links are being developed [110, 111, 112, 113]. It is not clear yet if these techniques will be able to be as good as optical bre techniques, mainly because of the eect of atmospheric turbulence [114, 115, 116]. 3.3.1 Free space propagation comparisons In the case of propagation in free space, if we suppose that t…”
BackgroundInfluential
- Authors
- Sinclair, L. C., Swann, W. C., Bergeron, H., Baumann, E., Cermak, M., Coddington, I., Deschênes, J.-D., Giorgetta, F. R., Juarez, J. C., Khader, I., Petrillo, K. G., Souza, K. T., Dennis, M. L., & Newbury, N. R.
- Affiliations
- National Institute of Standards and Technology (US)
- Université Laval (CA)
- Johns Hopkins University Applied Physics Laboratory (US)
- ORCID
- Venue
- Applied Physics Letters
- Publisher
- AIP Publishing
- Published
- 2016-10-10
- Volume
- 109
- Issue
- 15
- ISSN
- 0003-6951 (ISSN-L)
- 1077-3118
- PMC
- PMC5769483
- OpenAlex
- W2530475650
- Cited by
- 82
- References
- 4
- Citations by year
- 2026: 4 · 2025: 6 · 2024: 9 · 2023: 10 · 2022: 5 · 2021: 7 · 2020: 12 · 2019: 12 · 2018: 8 · 2017: 9
- FWCI
- 4.57
- Type
- journal article
- Language
- en
- Open access
- green
- www.ncbi.nlm.nih.gov
- Locations
- Applied Physics Letters (publishedVersion)
- PubMed (publishedVersion)
- PubMed Central (acceptedVersion)
- Funders
- National Institute of Standards and Technology (NIST)
- Defense Sciences Office, DARPA (PULSE)
- Topics
- Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Advanced Frequency and Time Standards
- Physical Sciences › Engineering › Electrical and Electronic Engineering › Optical Wireless Communication Technologies
- Physical Sciences › Computer Science › Computer Networks and Communications › Network Time Synchronization Technologies
- Keywords
- clock synchronization, atmospheric turbulence, strong turbulence, free-space optical links, adaptive optics, tip-tilt correction, Rytov variance, urban atmosphere, optical oscillators, microwave oscillators
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