Resolution 9 of the 23rd CGPM (2007)

On the revision of the mise en pratique of the definition of the metre and the development of new optical frequency standards

The 23rd General Conference,

considering that:

  • there have been rapid and important improvements in the performance of optical frequency standards,
  • femtosecond comb techniques are now used routinely for relating optical and microwave radiations at a single location,
  • National Metrology Institutes (NMIs) are working on comparison techniques for optical frequency standards over short distances,
  • remote comparison techniques need to be developed at an international level so that optical frequency standards can be compared,


  • the activities of the Joint Working Group of the Consultative Committee for Length and the Consultative Committee for Time and Frequency to review the frequencies of optically-based representations of the second,
  • the additions to the mise en pratique of the definition of the metre and to the list of recommended radiations made by the International Committee in 2002, 2003, 2005, 2006, and 2007,
  • the initiative taken by the International Bureau of Weights and Measures (BIPM) to raise the issue of how to compare optical frequency standards,

recommends that:

  • NMIs commit resources to the development of optical frequency standards and their comparison,
  • the BIPM works toward the coordination of an international project with the participation of NMIs, oriented to the study of the techniques which could serve to compare optical frequency standards.

DOI : 10.59161/CGPM2007RES9E

The reader should note that the official version of this Resolution is the French text

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