First international comparison of fountain primary frequency standards via a long distance optical fiber link

Abstract

We report on the first comparison of distant caesium fountain primary frequency standards (PFSs) via an optical fiber link. The 1415 km long optical link connects two PFSs at LNE-SYRTE (Laboratoire National de métrologie et d'Essais - SYstème de Références Temps-Espace) in Paris (France) with two at PTB (Physikalisch-Technische Bundesanstalt) in Braunschweig (Germany). For a long time, these PFSs have been major contributors to accuracy of the International Atomic Time (TAI), with stated accuracies of around $3\times 10^{-16}$. They have also been the references for a number of absolute measurements of clock transition frequencies in various optical frequency standards in view of a future redefinition of the second. The phase coherent optical frequency transfer via a stabilized telecom fiber link enables far better resolution than any other means of frequency transfer based on satellite links. The agreement for each pair of distant fountains compared is well within the combined uncertainty of a few 10${}^{-16}$ for all the comparisons, which fully supports the stated PFSs' uncertainties. The comparison also includes a rubidium fountain frequency standard participating in the steering of TAI and enables a new absolute determination of the ${}^{87}$Rb ground state hyperfine transition frequency with an uncertainty of $3.1\times 10^{-16}$. This paper is dedicated to the memory of André Clairon, who passed away on the 24${}^{th}$ of December 2015, for his pioneering and long-lasting efforts in atomic fountains. He also pioneered optical links from as early as 1997.

References in corpus (15)

• A clock network for geodesy and fundamental science
• Improved limit on a temporal variation of $m_p/m_e$ from comparisons of Yb${}^{+}$ and Cs atomic clocks
• Progress in Atomic Fountains at LNE-SYRTE
• Kerr-lens mode-locked lasers as transfer oscillators for optical frequency measurements
• Searching for an oscillating massive scalar field as a dark matter candidate using atomic hyperfine frequency comparisons
• Realization of a time-scale with an accurate optical lattice clock
• Brillouin amplification supports $1\times 10^{-20}$ accuracy in optical frequency transfer over 1400~km of underground fibre
• Cascaded optical fiber link using the Internet network for remote clocks comparison
• Optical to microwave clock frequency ratios with a nearly continuous strontium optical lattice clock
• Distributed cavity phase frequency shifts of the caesium fountain PTB-CSF2
• Contributing to TAI with a Secondary Representation of the SI Second
• Evaluation of Doppler Shifts to Improve the Accuracy of Primary Atomic Fountain Clocks
• Landau Level Collapse in Gated Graphene Structures
• Magnetic ordering and structural phase transitions in strained ultrathin SrRuO${}_3$/SrTiO${}_3$ superlattice
• Optical Stabilization of a Microwave Oscillator for Fountain Clock Interrogation

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