Time & Frequency Transfer
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Director of Business Development & Sales, Quantum Sensors
Turn-key industry-grade solution for optical frequency transfer over optical fibers
iXblue proposes all the hardware and software to enable long-haul optical frequency dissemination over optical fibers. Regeneration Laser Stations and bi-directional optical amplifiers are cascaded along an optical fiber to cover distances as long as thousands of kilometers while preserving the frequency stability provided by the best optical clocks in the world. Our technology was designed to transfer the metrological optical reference signal on a dark channel of the DWDM spectrum in parallel of Internet data traffic, but it can also work on a dark fiber. iXblue offers the world’s only industry-grade solution at this level of performance.
Metrology system turned into certified industry-grade turnkey devices
The Regeneration Laser Station (RLS)
The RLS is a fully automated laser repeater station dedicated to long-distance optical frequency transfer using optical fibers. This unique industry-grade regeneration laser station has been developed in collaboration with LPL (Univ. Paris 13) and LNE-SYRTE (Observatoire de Paris) laboratories, in the frame of the REFIMEVE+ project.
The regeneration of the reference optical signal is achieved thanks to the heterodyne optical phase-locking of an integrated ultra low-noise laser diode on the reference signal. The regeneration station actively compensates for the phase noise accumulated due to the propagation along the fiber. As a result, it is an equipment of choice for state-of-the-art optical clock remote comparisons.
- Frequency stability at a level of 10-20
- Compatible with DWDM telecom networks (dark channel and dark fiber).
- Robustness: the frequency lock remains locked for month without any action required from the user. It is robust with regard to temperature variations and vibrations.
- Fully Automated Phase-Lock Loops
- Remote access and real-time data retrieval
The supervision tool
iXblue’s solution for optical frequency transfer can be deployed within a few days and has shown to provide uptimes as high as 99 % over a week. This is enabled by the remote and automated operation of the hardware supervised by a global supervision tool. The supervision tool is composed of:
- A supervision software: to monitor and control the REFIMEVE+ performances
- A database: store all the information useful to the network management
- A human-machine interface: for end users, academic teams and the telecom network manager
The supervision software is in charge of
- Monitoring the proper functioning and remotely control the equipment parameters in real-time.
- Detecting and managing bugs and alarms (cycle slips, polarization optimizations, …)
- Uploading the information collected on the field and store in the database (alarm, events, …)
- Administrating and troubleshooting system configurations
- Pre-processing data: outliers detection, Allan Deviation calculation, …
The supervision tool of the REFIMEVE+ network currently monitors more than 150 pieces of equipment (EDFA, RLS, frequency counters). It enables the secured full remote access to all the equipment (RLS, ES, UM, EDFA) via the hosting telecom network infrastructure.
- Fully secured communication for supervision protocol: SSH, SNMP
- Supervision tool deployable through usual internet connection
- User-friendly webapp interfaces
- Remote access and real-time data retrieval
The Repeater Laser Station (RLS) is a stand-alone system that actively compensates the phase noise introduced by the fiber links and provides an ultra-stable output laser in the ITU channel 44 (1542.14nm) (other wavelengths on demand). It enables also to cascade fiber links in order to set-up long-distance frequency dissemination. It has been designed to be installed in a Telecom network nodes in respect to NF/EN 60950-1 and NF/EN 60825-1 norms. It can work both on a dark channel and on a dark fiber.
Fig. 1: Fractional frequency instability calculated from data recorded with Λ-counter and 1 s gate time versus averaging time. Dark red squares, modified Allan deviation for a compensated 200 km laboratory link; light red circles, modified Allan deviation for the free-running 200 km laboratory link; dark green stars, modified Allan deviation for a short link to estimate the noise floor of the RLS; light green diamonds, modified Allan deviation for the free-running short link.
Fig 2: End-to-end phase fluctuations after propagation over a 680 km fiber link.
Data from F. Guillou-Camago et al., « First industrial-grade coherent fiber link for optical frequency standard dissemination», Applied Optics, Vol. 57, No. 25 (2018)
After several years of industrialization of RLS, iXblue is able to commit to excellent performances.
|Central wavelength||1542 nm (ITU Channel 44)
(other wavelengths in option)
RLS NOISE FLOOR
|Relative short term frequency stability||< 3×10-17 @1 s|
|Relative long term frequency stability (noise floor)||< 2×10-20 @103 s|
|Typical accuracy of fiber link||< 1e-19, depending on link characteristics|
|Temperature sensitivity of the interferometer||< 1 fs / °C|
|Typical maximum range between 2 RLS on standard telecom fiber links||500 km|
|MASS AND DIMENSIONS|
|Number of boxes||2|
|Mass||16.7 kg for the RLS|
|4 kg for power supply|
|Dimensions||5U 19’’ rack for the RLS
(485 mm x 222 mm x 540 mm)
|2U 19’’ rack for the power supply unit
(485 mm x 90 mm x 250 mm)
|Input power||-60dBm < P < 3dBm|
|Wavelength||1542nm + custom|
|SYSTEM INTERFACE & CONTROL|
|Communication protocol||SSH, SNMP|
|Degree of Ingress Protection||IP 30|
|ENVIRONMENTAL & PHYSICAL SPECIFICATIONS|
|Operating temperature||[15 ; 35] °C|
|Storage temperature||[5 ; 30] °C|
|Humidity||Maximum relative humidity 80 % for temperatures up to 31 °C decreasing linearly to 50 % relative humidity at 40 °C|
First industrial-grade coherent fiber link for optical frequency standard dissemination
Applied Optics, Vol. 57, No. 25 (2018)
We report on a fully bidirectional 680 km fiber link connecting two cities for which the equipment, the setup, and the characterization are managed for the first time by an industrial consortium. The link uses an active telecommunication fiber network with parallel data traffic and is equipped with three repeater laser stations and four remote double bidirectional erbium-doped fiber amplifiers.Download
An accurate and robust metrological network for coherent optical frequency dissemination
New J. Phys. 23 053027 (2021)
We introduce multi-branch repeater laser stations (MLSs) for the dissemination of an ultra-stable signal from one point to multiple users and the simultaneous evaluation of the stability and accuracy of multiple links. We perform the study of the noise floor of this new instrument.Download