Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Physical Review Applied

Coherent Optical-Fiber Link Across Italy and France

Cecilia Clivati, Marco Pizzocaro, Elio K. Bertacco, Stefano Condio, Giovanni Antonio Costanzo, Simone Donadello, Irene Goti, Michele Gozzelino, Filippo Levi, Alberto Mura, Matias Risaro, Davide Calonico, Mads Tønnes, Benjamin Pointard, Maxime Mazouth-Laurol, Rodolphe Le Targat, Michel Abgrall, M. Lours, Herve Le Goff, L. Lorini, Paul-Éric Pottie, Etienne Cantin, Olivier Lopez, Christian Chardonnet, Anne Amy‐Klein

Published Nov 3, 2022• 33 citations
Publisher

Abstract

The dissemination of atomic clocks with fiber-based techniques finds application in the fields of metrology, fundamental physics, navigation, and spectroscopy but is a challenge in terms of reliability, maintenance, and performance. Here, we describe the realization of a 1023-km-long fiber link between the metrological institutes of Italy and France that shares the infrastructure with the Internet traffic and exploits segmentation in shorter, cascaded spans to fight optical losses exceeding 280 dB. With four months of quasicontinuous operation of this link, we compared the $\mathrm{Cs}$, $\mathrm{Rb}$, and $\mathrm{Yb}$ atomic clocks at our laboratories, highlighting the potential of this tool to assess the clock uncertainty budgets, characterize advanced satellite techniques, and develop optical timescales. The integration of the metrological, fiber-based infrastructures in the two countries, connecting photonics and spectroscopy laboratories as well as telescope facilities, provides the research community with a physical layer over which applications can be built on.

DOI
10.1103/physrevapplied.18.054009

Related papers

Realization of a phase-coherent optical fiber link for the comparison of remote atomic clocks

Cecilia Clivati

This thesis describes the realization of a facility for the high-accuracy frequency dissemination on a continental scale. This project was developed at the Optics division of the Italian National Metrology Institute (INRIM), which is in charge of the realization and operation of the atomic primary frequency standards, of their dissemination, and cooperates to the International Atomic Time generation. Frequency dissemination is now based on satellite techniques; however, the resolution provided by these methods does not cope with the accuracy and stability of newgeneration frequency standards. For instance, more than 10 days of measurement are needed to effectively compare primary standards, and years would be necessary to compare optical clocks via satellite links. On the other hand, it has been demonstrated that systems based on optical fibers can improve the resolution by about 5 orders of magnitude with respect to satellite techniques. This is the reason why many national metrology institutes in Europe are cooperating to develop a network for frequency dissemination and clocks comparisons all across the continent. This technique is based on the transmission of a narrow-linewidth laser along a standard telecom fiber. At the metrological laboratory, the frequency is measured with respect to a frequency standard, while at the remote link end it is extracted and used as a frequency reference. However, temperature changes, acoustic noise, air flows can degrade the stability of the delivered frequency, and must therefore be compensated. This is done through a Doppler cancellation technique, in which the light travels twice in the optical fiber in opposite directions. This is different from what happens in telecom links, which are inherently bidirectional. Dedicated instruments have therefore been developed. This thesis describes the realization of a phase-stabilized optical link between INRIM and the European Laboratory for Non Linear Spectroscopy in Florence, where an optical clock based on Sr atoms was under development at the time of measurements. This clock has been compared to the INRIM primary standard via the optical link. I worked on the realization of the ultrastable laser sources, on the development and characterization of the optical and electronics apparatus, and at the development of the metrological chain for the remote clocks comparison. This thesis also describes some novel techniques which we investigated in the framework of this project, and new applications of optical fiber links. During my studies I spent two months at the Laboratoire National d'Essais-Systemes de Référence Temps-Espace (LNE-SYRTE) in Paris, where I cooperated to the realization of an ultrastable laser source based on an optical delay line. This is reported in the thesis as well

•Jan 1, 2014•0 citations

Optical fiber link for ultra-stable frequency dissemination and atomic clock comparisons

Anne Amy‐Klein, Nicolas Quintin, N. Chiodo +42 more

The transfer of ultra-stable frequencies between distant laboratories is required by many applications from fundamental metrology to high-precision measurements. For that purpose, optical fibre links have been intensively studied over the last decade. They have demonstrated impressive results far beyond the GPS capabilities on distances up to 2000 km, thanks to an active compensation of the fiber propagation noise.Up to now, optical links has been mainly implemented between two labs, when future applications will require the development of metrological fiber networks. Towards this goal, we have developed a few techniques which allow us to distribute the ultrastable optical signal to many users simultaneously. We have designed repeater laser stations, which can be used to build a cascaded link or to distribute the ultrastable signal among two optical links [1]. These stations allow us also to compare the output end signals of two optical links. These versatile stations will be a key-component of the national metrological network currently being developed in France within the Refimeve+ project. To complete the network, we have demonstrated the extraction of the ultrastable signal from a main link and its seeding to a secondary link [2].Optical links are already been successfully used for clocks comparison. Recently we were able to compare the atomic clocks of the French and German National Metrology Institutes through two connected optical links of total length 1415-km [3]. We found that the two fully independent Sr lattice optical clocks at the two sites agreed to better than 5x10-17 limited only by the clocks uncertainties. A fractional statistical uncertainty of 3x10-17 was reached after only 1000 s averaging time, which is 10 times better, and more than four orders of magnitude faster than with any other existing frequency transfer method. The atomic fountain primary frequency standards from the two institutes were also compared and they were found to agree well within their combined uncertainties of a few 10-16 [4].

•Jan 1, 2017•0 citations

A Coherent Optical Fiber Link for Very Long Baseline Interferometry

Cecilia Clivati, Roberto Gabriel Aiello, G. Bianco +14 more

We realize a phase-stabilised optical fiber backbone that connects the Italian National Metrology Institute with two radio telescopes over a 600 km baseline. This allows referencing of Very Long Baseline Interferometry (VLBI) facilities with the best atomic frequency standards available today and the implementation of a common-clock architecture, which we are now using to assess VLBI ultimate performances.

Conference on Lasers and Electro-Optics•Jan 1, 2020•0 citations

A 1800-km optical fiber link for metrology, geodesy, and clock comparison

Mario Siciliani de Cumis, Cecilia Clivati, Luigi Santamaria Amato +18 more

Nowadays, optical fiber links are key elements in optical metrology, spectroscopy, quantum communication and geodesy. In geodetic Very Long Baseline Interferometry, a local maser is responsible for providing time and frequency reference at radiotelescope. Here, we present our recent results on frequency dissemination using a coherent fiber link 1800 km long from Turin to Medicina and Matera, Italy. Metrological reference disseminated via fiber link improve the stability of about two order with respect to the local H-maser clocks. This kind of dissemination paves the way to VLBI observation using a remote clock reference on the Italian and European radio observatories.

Optical and Quantum Sensing and Precision Metrology II•Feb 25, 2020•0 citations

650-km fiber link for optical frequency dissemination and remote clocks comparison in Italy

Cecilia Clivati, Claudio Eligio Calosso, Matteo Frittelli +9 more

We realized a 650-km optical fiber link in Italy for frequency dissemination and remote clocks comparison. We present its implementation and characterization at the 5x10-19 uncertainty level, discussing its future applications.

•Jan 1, 2014•0 citations

Réseaux de liens fibrés en métrologie pour la dissemination de fréquence : étude, exploitation, et sensibilités à l'effet Sagnac et autres perturbations terrestres

Mads Tønnes

Atomic clocks are the modern tools of timekeeping. Ever since the redefinition of the second in 1967 based on an atomic transition of Cesium 133, the atomic clocks have improved drastically. This has lead to many technological advancements the last 55 years, many of which require precise transfer of time and frequency signals, a prominent example being the Global Positioning System (GPS). With the recent advancements of the last generation of state-of-the-art atomic clocks, so called optical clocks, traditional means of disseminating their signals without degrading their performance are no longer adequate. The implementation of a new technology for such purposes has in recent years been implemented in several countries around the world, which utilizes optical fibers as a medium to transfer and compare the signals of the atomic frequency references.In this thesis, I discuss the exploitation of such an optical fiber network in France. I discuss the general noise processes of such fiber links, and their technical and fundamental limits. In-depth studies of several applications of a fiber network is presented. These include the evaluation of the uncertainty contribution of the French fiber network to the comparison of optical clocks. I also show studies of the use of fiber networks for the sensing of effects arising from the Earth. This includes the sensing of the Sagnac effect in a fiber link deployed in a ring topology around Paris, a study of the detection of earthquakes with the French fiber network, and a discussion of the prospects of the use of such a technology.

•Nov 21, 2022•0 citations
The dissemination of atomic clocks with fiber-based techniques finds application in the fields of metrology, fundamental physics, navigation, and spectroscopy but is a challenge in terms of reliability, maintenance, and performance. Here, we describe the realization of a 1023-km-long fiber link between the metrological institutes of Italy and France that shares the infrastructure with the Internet traffic and exploits segmentation in shorter, cascaded spans to fight optical losses exceeding 280 dB. With four months of quasicontinuous operation of this link, we compared the Cs\mathrm{Cs}Cs, Rb\mathrm{Rb}Rb, and Yb\mathrm{Yb}Yb atomic clocks at our laboratories, highlighting the potential of this tool to assess the clock uncertainty budgets, characterize advanced satellite techniques, and develop optical timescales. The integration of the metrological, fiber-based infrastructures in the two countries, connecting photonics and spectroscopy laboratories as well as telescope facilities, provides the research community with a physical layer over which applications can be built on.
This thesis describes the realization of a facility for the high-accuracy frequency dissemination on a continental scale. This project was developed at the Optics division of the Italian National Metrology Institute (INRIM), which is in charge of the realization and operation of the atomic primary frequency standards, of their dissemination, and cooperates to the International Atomic Time generation. Frequency dissemination is now based on satellite techniques; however, the resolution provided by these methods does not cope with the accuracy and stability of newgeneration frequency standards. For instance, more than 10 days of measurement are needed to effectively compare primary standards, and years would be necessary to compare optical clocks via satellite links. On the other hand, it has been demonstrated that systems based on optical fibers can improve the resolution by about 5 orders of magnitude with respect to satellite techniques. This is the reason why many national metrology institutes in Europe are cooperating to develop a network for frequency dissemination and clocks comparisons all across the continent. This technique is based on the transmission of a narrow-linewidth laser along a standard telecom fiber. At the metrological laboratory, the frequency is measured with respect to a frequency standard, while at the remote link end it is extracted and used as a frequency reference. However, temperature changes, acoustic noise, air flows can degrade the stability of the delivered frequency, and must therefore be compensated. This is done through a Doppler cancellation technique, in which the light travels twice in the optical fiber in opposite directions. This is different from what happens in telecom links, which are inherently bidirectional. Dedicated instruments have therefore been developed. This thesis describes the realization of a phase-stabilized optical link between INRIM and the European Laboratory for Non Linear Spectroscopy in Florence, where an optical clock based on Sr atoms was under development at the time of measurements. This clock has been compared to the INRIM primary standard via the optical link. I worked on the realization of the ultrastable laser sources, on the development and characterization of the optical and electronics apparatus, and at the development of the metrological chain for the remote clocks comparison. This thesis also describes some novel techniques which we investigated in the framework of this project, and new applications of optical fiber links. During my studies I spent two months at the Laboratoire National d'Essais-Systemes de Référence Temps-Espace (LNE-SYRTE) in Paris, where I cooperated to the realization of an ultrastable laser source based on an optical delay line. This is reported in the thesis as well
The transfer of ultra-stable frequencies between distant laboratories is required by many applications from fundamental metrology to high-precision measurements. For that purpose, optical fibre links have been intensively studied over the last decade. They have demonstrated impressive results far beyond the GPS capabilities on distances up to 2000 km, thanks to an active compensation of the fiber propagation noise.Up to now, optical links has been mainly implemented between two labs, when future applications will require the development of metrological fiber networks. Towards this goal, we have developed a few techniques which allow us to distribute the ultrastable optical signal to many users simultaneously. We have designed repeater laser stations, which can be used to build a cascaded link or to distribute the ultrastable signal among two optical links [1]. These stations allow us also to compare the output end signals of two optical links. These versatile stations will be a key-component of the national metrological network currently being developed in France within the Refimeve+ project. To complete the network, we have demonstrated the extraction of the ultrastable signal from a main link and its seeding to a secondary link [2].Optical links are already been successfully used for clocks comparison. Recently we were able to compare the atomic clocks of the French and German National Metrology Institutes through two connected optical links of total length 1415-km [3]. We found that the two fully independent Sr lattice optical clocks at the two sites agreed to better than 5x10-17 limited only by the clocks uncertainties. A fractional statistical uncertainty of 3x10-17 was reached after only 1000 s averaging time, which is 10 times better, and more than four orders of magnitude faster than with any other existing frequency transfer method. The atomic fountain primary frequency standards from the two institutes were also compared and they were found to agree well within their combined uncertainties of a few 10-16 [4].
Nowadays, optical fiber links are key elements in optical metrology, spectroscopy, quantum communication and geodesy. In geodetic Very Long Baseline Interferometry, a local maser is responsible for providing time and frequency reference at radiotelescope. Here, we present our recent results on frequency dissemination using a coherent fiber link 1800 km long from Turin to Medicina and Matera, Italy. Metrological reference disseminated via fiber link improve the stability of about two order with respect to the local H-maser clocks. This kind of dissemination paves the way to VLBI observation using a remote clock reference on the Italian and European radio observatories.
Atomic clocks are the modern tools of timekeeping. Ever since the redefinition of the second in 1967 based on an atomic transition of Cesium 133, the atomic clocks have improved drastically. This has lead to many technological advancements the last 55 years, many of which require precise transfer of time and frequency signals, a prominent example being the Global Positioning System (GPS). With the recent advancements of the last generation of state-of-the-art atomic clocks, so called optical clocks, traditional means of disseminating their signals without degrading their performance are no longer adequate. The implementation of a new technology for such purposes has in recent years been implemented in several countries around the world, which utilizes optical fibers as a medium to transfer and compare the signals of the atomic frequency references.In this thesis, I discuss the exploitation of such an optical fiber network in France. I discuss the general noise processes of such fiber links, and their technical and fundamental limits. In-depth studies of several applications of a fiber network is presented. These include the evaluation of the uncertainty contribution of the French fiber network to the comparison of optical clocks. I also show studies of the use of fiber networks for the sensing of effects arising from the Earth. This includes the sensing of the Sagnac effect in a fiber link deployed in a ring topology around Paris, a study of the detection of earthquakes with the French fiber network, and a discussion of the prospects of the use of such a technology.