Recommendation 3 of the 11th CCL (2003)

Future organization of optical frequency measurements

The Consultative Committee for Length,

considering:

• the high level of agreement already demonstrated in comparisons between the travelling femtosecond combs from the International Bureau of Weights and Measures (BIPM) and the East China Normal University (ECNU) with the comb system at the National Institute of Standards and Technology (NIST);
• the requirement for validation of comb measurement capability at different laboratories used to provide absolute frequency measurements of optical frequency standards and stabilized lasers;
• the potential for future BIPM.L-K11 key comparison to incorporate both laser heterodyne comparisons and calibration by comb;
• the relative complexity of current comb facilities compared to portable laser standards;
• the impracticality of BIPM travelling combs to undertake a large programme of comb comparisons;

recommends that:

• the BIPM undertake travelling comb comparisons only at the highest level of comparison accuracy, which would require a high level of stability and reproducibility on the part of the optical frequency standard;
• calibration of most stabilized laser standards and validation of comb facilities measuring such stabilized laser standards at other laboratories could proceed on a regional basis, by accessing the regional comb systems participating in the high-level comb comparisons;
• the BIPM continue to offer laser calibration using comb and laser heterodyne comparisons, where appropriate, in its own laboratories.

DOI : 10.59161/CCL2003REC3E