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Technical Units 2-13 and 2-06 :

Expertise and time-frequency calibration under accreditation - NF EN ISO / IEC 17025
Time-frequency domains and electricity / magnetism
Presentation of the LFTB
FEMTO-ST is a laboratory associated with the LNE (National Laboratory of Metrology and Testing) under the Technical Unit 2-13 of the LTFB (Time Frequency Laboratory of Besançon).
The LTFB was born in 2008 from the merger of 2 laboratories :
• Technical Unit 2-06: calibrations in time, frequency, time interval (Observatory)
• Technical Unit 2-13: spectral density calibrations of phase noise and short-term frequency stability  (FEMTO-ST)
The calibration possibilities of the LTFB can be consulted on the link:

Goals and benchmarking activities

The goal is to carry out calibrations (connection to a primary reference) under accreditation COFRAC (French Accreditation Committee).

UT 2-06: This activity focuses on the characterization of frequency sources by the measurement of frequency drift, the measurement of time intervals, the measurement of frequency instability as a function of the measurement time (tau): Long-term (tau ≥ 100 s and up to 10 days or more).

UT 2-13: This activity deals with the characterization of oscillators of high stability OUS (Ultra Stable Oscillators), frequency generators, frequency synthesizers and also cesium and rubidium standards which are the local references of laboratories Applicants:
- or in the TIME DOMAIN by measuring the frequency instability as a function of the measurement time (tau) characterized by calculating the Allan standard deviation (sigma (tau) with 0.1 s ≤ tau ≤ 100 S)

- or in the SPECTRAL DOMAIN (Frequency 5MHz up to 26GHz) by measuring the spectral density of the phase or frequency fluctuations for Fourier frequencies ranging from 1Hz to 100MHz.

The LNE-LTFB also regularly conducts inter-laboratory comparisons (CIL) to check the consistency of the results. Measurements carried out in the various accredited time-frequency laboratories installed on the national territory (a CIL is in progress in 2020, a reference frequency standard will travel between the laboratories involved).

Participation in international projects:
CMC: As part of Euramet, the laboratory is involved in the implementation of CMC (Calibration Metrology Capabilities) in the frequency domain for short-term frequency stability measurements and in the field of measurement Spectral density of phase noise. The CMCs are then centralized at the BIPM (International Bureau of Weights and Measures). The CMCs were approved and published in September 2006 (phase noise) and January 2009 (short-term frequency stability):

CMCs have recently been revised at the national level in collaboration "with the Paris Observatory (LNE-SYRTE); the revisions have been reviewed and approved by the five BIPM-affiliated world metrology regions, which published them in July 2019.

Examples of scientific developments and achievements at UT2-13:

- Optoelectronic bench for measurements of phase noise in the X band (8 to 12 GHz)

A project contract "LNE / DRST 10 7 002", started in 2011, enabled LTFB-UT 2-13 to develop a new state-of-the-art phase noise measurement bench whose objective of this project Was to produce an optoelectronic bench of phase noise measurements with optical delay lines by decreasing the noise floors by intercorrelation up to -170 dB.rad² / Hz at 1kHz of the carrier, chosen initially around Of 10 GHz. This is a new measurement technique that combines the advantages of microwaves with those of optics. The interest is to be able to calibrate frequency sources without referring to a standard. The measurement is done directly and does not require comparison. This bench was accredited by COFRAC in July 2013 at 10GHz and the request for extension on the 8-12GHz range is currently being studied at COFRAC.

- Frequency accuracy measuring bench (5 and 10 MHz):

Maintaining measurement capabilities with, for example, the development and development of a new frequency accuracy measuring bench for frequency sources of 5MHz or 10MHz to alleviate the aging of the devices. This new bench is operational and it is planned to bring it into our accreditation soon.


In 1973: Birth of the calibration activities within the LPMO (Laboratory of Physics and Metrology of Oscillatorsand l'obervatoire of Besançon. The certifying body was first the BNM (Bureau National de Métrologie), then the certifying function was separated from the metrological body to become independent under the name
initially FRETAC, then COFRAC* since 1995. The BNM, the organization in charge of national metrology, became LNE in 2005.

In May 2001: Signature of an association contract between the BNM and the CNRS.
In March 2002: Validation by the COFRAC of the technical file of the laboratory containing the precise description of the methods of calibrations used as well as all the uncertainties associated with the results of calibrations.
In July 2002: Transition to the new ISO 17025 standard.
January 1, 2004: FEMTO-ST replaces the LPMO. January 1st, 2005: BNM activities transferred to the LNE (National Laboratory of Essays) March 1st, 2008: Merger of the accredited laboratories of the Observatory of Besançon (N ° 2-06) and of FEMTO-ST (N ° 2-13) within a new structure: LTFB, which currently has a dozen permanent staff.

Since then, LNE-LTFB has been audited every 15 months by COFRAC to check that the work carried out complies with the standard and to renew its accreditation. LNE-LTFB has implemented the major changes made to version 2017 of standard NF/EN/ISO/CEI 17025-2017 and its accreditation was renewed according to this version in November 2019.


Director of LNE-LTFB (UT 2-06 + UT 2-13): François MEYER (Tel: 33 (0) 3 81 66 69 27)
Administrative contact: Fabienne GRAND-LOCATELLI (Tel: 33 (0) 3 81 66 69 31)
Scientific manager : Jacques MILLO (Tel: 33 (0) 3 81 40 29 24)
Technical Manager UT 2-06: François MEYERLNE-LTFB, accredited technical unit 2.06, OSU THETA, Besançon Observatory,41, avenue de l'Observatoire, PO Box 1615, F25010 BESANÇON Cedex, France
Technical Manager UT 2-13: Jacques MILLO (Tel: 33 (0) 3 81 40 29 24)• LNE-LTFB, accredited technical unit 2.13, CNRS / ENSMM / FEMTO-ST / Dpt.TF,26 Chemin de l'épitaphe, F25030 Besançon Cedex, France


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