The Practical Realization of the Meter in Portugal

  1. French College of Metrology
  1. F. Saraiva and
  2. S. Gentil

Published Online: 3 FEB 2010

DOI: 10.1002/9780470611371.ch16

Transverse Disciplines in Metrology

Transverse Disciplines in Metrology

How to Cite

French College of Metrology (2010) The Practical Realization of the Meter in Portugal, in Transverse Disciplines in Metrology, ISTE, London, UK. doi: 10.1002/9780470611371.ch16

Author Information

  1. Laboratório Central de Metrologia, Instituto Portuguěs da Qualidade Rua António Gião 2, 2829–513 Caparica, Portugal

Publication History

  1. Published Online: 3 FEB 2010
  2. Published Print: 1 JAN 2009

ISBN Information

Print ISBN: 9781848210486

Online ISBN: 9780470611371



  • beat-frequency;
  • sensitivity coefficients;
  • traceability;
  • absolute frequency;
  • output frequency


This paper reports the measured values of the laser systems IPQ2 and IPQ3 performed during recent years at IPQ for the evaluation of the output frequency and the sensitivity coefficients of the lasers: the iodine temperature and pressure, the modulation width and the power coefficients. These parameters are required when the lasers are used as a standard in applications such as frequency calibrations.

The laser systems IPQ2 and IPQ3 are He-Ne lasers stabilized on the saturated absorption of 127I2 at λ ≅ 633 nm which are able to satisfy requirements set by the Comité International des Poids et Measures (CIPM) [1] and they represent one of the two possibilities to perform the practical realization of the definition of the meter.

At IPQ, the other possibility to perform the practical realization of the definition of the meter is by means of the optical comb frequency synthesizer (OFS) a femtosecond Kerr-lens mode-locked laser with an optical fiber based on photonic crystals. This device links the optical frequencies to the frequency of the Cs microwave standard (the national standard for the second).

This paper also describes the validation process of the frequency measurements performed at IPQ, through the comparison of its own frequency values with the ones measured by absolute frequency using the OFS and with the values obtained in the international key comparisons participations at the BIPM (BIPM. L-K10 and BIPM. L-K11).