Time & Frequency Reference


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Jean Lautier-Gaud

Director of Business Development & Sales, Quantum Sensors

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A high-performance frequency standard based on cold atoms

Thanks to the advances of Quantum Technologies, iXblue provides a turn-key atomic clock delivering an RF reference signal featuring a relative frequency stability at a level of 10-15.

These frequency reference and measurement technique are recognized by the BIPM (Bureau International des Poids et Mesures) as an official secondary frequency standard. The Muclock thus delivers a frequency reference signal that can be used for representation of the definition of the SI second.

Muclock features within a single device unmatched performances in terms of short and long-term frequency stability, as well as accuracy and predictability. It therefore offers a very interesting alternative to usual Hydrogen Maser / Caesium clocks ensembles for the generation of highly stable time scales, among others.

Compact, robust and turn-key system

Originally inspired by the atomic fountains developed at LNE-SYRTE, our product is based on several technological innovations which allow to propose a compact and robust, turn-key and fully automated system. MuClock provides a new solution that brings the performances of cold atom frequency metrology, in a stand-alone, turn-key equipment.

The approach provided by iXblue relies on the laser manipulation of cold atoms and the microwave interrogation of a large atomic cloud, cooled down with laser beams to a temperature of a few μK. This unique atomic medium shows an exceptional stability over time, independent of the external conditions. This technique offers the possibility to perform over months spectroscopy measurements with an exceptionally high signal-to-noise ratio and a remarkable stability.

Key Operational features

Installation: automated (no optical alignment, no mechanical assembly, no pumping required prior to measuring)

Autonomy: Transport and storage for several days without any power supply will not affect measurement capability nor require additional pumping (sealed dropping chamber)

Software: Dedicated and user-friendly data acquisition and system controller software
Automated starting procedure
Automated self-calibration procedures
Remote monitoring and real-time data retrieval

Auxiliary sensors: The physics package of the Muclock houses a pressure gauge, temperature sensors

Providing high-quality data

The Muclock provides an RF micro-wave signal that can be analyzed by processing its Allan Deviation.

Example of typical data provided by the Muclock. Allan Deviation of a 15-day long time series showing a short-term frequency stability of 3.2 10-13 at 1 s and reaching a long-term stability of 10-15.

Key technology: Isotropic Laser Cooling

The general idea behind the system design is to prepare the cold atom cloud inside the microwave cavity and interrogate the atoms at the same place. This is achieved with isotropic laser cooling (ILC). ILC utilizes the refl ections on the inner surface of the microwave cavity to produce a well-controlled laser fi eld for effi cient cooling of the atoms. The preparation of the atomic cloud is quickly followed by its microwave interrogation. This measurement sequence is repeated at a 10-Hz repetition rate.

With this approach, we therefore obtain performances close to atomic fountains with a signifi cant weight and volume reduction and improvement in compactness, ease of use, and robustness to the environment.

High-reliability fibered optical components

The laser system developed by iXblue relies on the use of lasers operating at 1560 nm. This approach therefore gives access to a wide variety of high performance fibered optical components, originally developed for high-bit-rate optical communication systems. Thanks to the technological efforts conducted over the last 20 years by the telecom industry, these components present unique features:

  • fibered components: no optical alignment required
  • remarkable optical and electrical performances
  • compliance with Telcordia qualification procedures (extended temperature range)
  • high reliability (lifetime > 50 000 h).



Frequency stability 1 s ≤ 4.0 10-13
10 s ≤ 9.5 10-14
100 s ≤ 3.0 10-14
1000 s ≤ 9.5 10-15
10000 s ≤ 3.0 10-15
1 day ≤ 2.0 10-15
Flicker floor ≤ 2.0 10-15
(@ 10 days)
Phase noise Offset (Hz) 5MHz Output
1 -121 dBc
10 -151 dBc
100 -163 dBc
1,000 -168 dBc
10,000 -176 dBc
100,000 -178 dBc
Accuracy ≤ 5 10-15
(under metrological evaluation)


Number of boxes 1
Total mass 135 kg
Dimensions h = 155 cm x w = 55 cm x d = 80 cm
Output frequencies 5, 10, 100 MHz
Synchronization 1 PPS


Control system On-board computer
User Interface Dedicated software
OS of the operating computer Linux
Remote Monitoring ? Yes


Operating power consumption < 250 W



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    F.X.Esnault, N.Rossetto, D.Holleville, J.Delporte, N.Dimarcq

    Advances in Space Research 47 – March 2011

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