INTERNATIONAL COMPARISONS OF HE-NE LASERS STABILIZED WITH I-127(2) ATLAMBDA-APPROXIMATE-TO-633 NM (JULY 1993 TO SEPTEMBER 1995) PART I - GENERAL

After the adoption of the new mise en pratique of the definition of th e metre in 1992, a wide-ranging programme of laser comparisons at lamb da approximate to 633 nm, the most used of the recommended wavelengths , was carried out involving national laboratories and the Bureau Inter national des Poids et Mesures (BIPM). During the period July 1993 to S eptember 1995, six grouped and five bilateral comparisons were made in volving thirty-five national laboratories. This report will comprise s ix different parts. The first part, this paper, describes the general conditions for such comparisons and the results of the unpublished bil ateral comparisons, and in the five following parts, the detailed resu lts of the grouped comparisons will be presented and discussed. Except for a few lasers which exhibited some malfunction, the frequency diff erences between the lasers being compared lay inside the standard unce rtainty (2,5 parts in 10(11)) given in the mise en pratique, once the lasers had been adjusted to have the recommended parameter values.