DOI: 10.5281/zenodo.17107693
title: Dataset for "Coordinated international comparisons between optical clocks connected via fiber and satellite links"

description: This dataset contains results from the comparison of optical clocks during the March 2022 campaign organized under the European Metrology Programme for Innovation and Research (EMPIR) Project ROCIT. The results are reported in T. Lindvall et al., "Coordinated international comparisons between optical clocks connected via fiber and satellite links," Optica 12, 843-852 (2025).

This dataset includes only the comparisons carried out via the European optical fibre newtork. The involved optical clocks are: INRIM Yb optical lattice clock IT-Yb1, LNE-SYRTE Sr optical lattice clock SYRTE-Sr2, LUH In+ ion clock PTB-In1, NPL Sr optical lattice clock NPL-Sr1, NPL Yb+(E3) ion clock NPL-E3Yb+3, PTB Sr optical lattice clock PTB-Sr3, PTB Yb+(E2) ion clock PTB-Yb1E2, PTB Yb+(E3) ion clock PTB-Yb1E3.

Data is organized in folders, one for each comparison.  Data is reported as fractional frequency ratios on a 1-s grid. The data follows the optical link data format developed for the EMPIR Projects OFTEN and ROCIT, and the European Partnership on Metrology Project TOCK. Timetags are reported in modified Julian date (MJD). A validity flag is given where 0 = invalid, valid otherwise. Each folder includes a yaml file with metadata required for generalized data processing. A Python package that can be used for data processing can be found on github. Inconsistencies have been observed in parts of the data, as discussed in Optica; users should refer to the paper for details and interpretation.

 

 
description: This work was carried out in the EMPIR project ROCIT 18SIB05.  This project has received funding from the EMPIR programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme. NPL acknowledges support by the UK government Department for Science Innovation and Technology through the National Measurement System Programme. NMIJ acknowledges support by the Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number 17H01151, 17K14367, and 22H01241, and JST-Mirai Program Grant Number JPMJMI18A1, Japan.PTB acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy EXC-2123 QuantumFrontiers (Project-ID 390837967) and SFB 1227 DQ-mat (Project-ID 274200144, within project B02 and B03); this work was partially supported by the Max Planck-RIKEN-PTB Center for Time, Constants and Fundamental Symmetries funded equally by the three partners. VTT acknowledges support by the Academy of Finland (decisions 339821 and 328786).The work at VTT is also part of the Academy of Finland Flagship Programme `Photonics Research and Innovation' (PREIN, decision 320168).Optical fiber links from the French REFIMEVE network are supported by Program ``Investissements d’Avenir'' launched by the French Government and implemented by Agence Nationale de la Recherche with references ANR-11-EQPX-0039 (Equipex REFIMEVE+) and ANR-21-ESRE-0029 (ESR/Equipex+ T-REFIMEVE).M. M.-L. received funding from the European Union's Horizon 2020 research and innovation programme under Grant Agreement No. 951886 (CLONETS-DS).M. T. received funding from DIM SIRTEQ network of Conseil Régional Île de France (ATH-2019 ONSEPA).Authors from NMIJ are indebted to the colleagues of Time Standards Group and Optical Frequency Measurement Group at NMIJ, and also of Yokohama National University. NMIJ acknowledges the Geospatial Information Authority of Japan for the determination of the geopotential value of the Yb optical clock at NMIJ.