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

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

Cecilia Clivati, Claudio Eligio Calosso, Matteo Frittelli, A. Godone, Mura A., F. Levi, Massimo E. Zucco, Davide Calonico, Denis V. Sutyrin, Tino G., Poli N., Costanzo G. A.

Published Jan 1, 2014• 0 citations
OpenAlex

Abstract

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.

Related papers

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

Optical frequency dissemination for metrology applications

Stefan Droste, Thomas Udem, Ronald Holzwarth +1 more

With the progress in the development of optical frequency standards grows the demand for the dissemination of stable optical frequencies. To date, optical fiber links constitute the most promising medium to bridge large geographical distances while still maintaining a high degree of frequency stability and accuracy. We investigated the transfer of an optical frequency along different fiber links during the past years and achieved a fractional instability and uncertainty at a level lower than 10 − 19 using fiber links with lengths of up to almost 2000 km. We give an overview of different techniques and methods that can be used in combination with optical fiber links to achieve a stable frequency transfer. The results of different fiber links are summarized and an outlook of future links is given.

Comptes Rendus Physique•Apr 8, 2015•20 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

Optical frequency transfer with a 1284 km coherent fiber link

Davide Calonico, Elio K. Bertacco, Claudio Eligio Calosso +10 more

We realized a coherent optical fiber link in Italy, with a fiber haul of 642 km. To characterize the link, we doubled the link to 1284 km, demonstrating a characterization technique based on the double round trip on a single fiber. The link is intended to significantly improve the frequency references used in radio-astronomy and precision measurements in atomic physics. The data analysis is based on the Allan deviation, whose expression is theoretically derived from the noise power spectrum. The demonstrated resolution is 3×10−19 in 1000 s and the uncertainty of the transfer is 5×10−19. The arming of a second fiber is avoided, and this could be rather beneficial to long hauls realizations for a continental fiber network for frequency and time metrology.

European Frequency and Time Forum•Jun 1, 2014•9 citations

Coherent Optical-Fiber Link Across Italy and France

Cecilia Clivati, Marco Pizzocaro, Elio K. Bertacco +22 more

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.

Physical Review Applied•Nov 3, 2022•33 citations

Record-breaking optical frequency dissemination over 2,067 km fiber network

Ziyang Chen, Xu KEmi, Hong Guo

Abstract A research team demonstrated a 2067-km field-deployed optical frequency dissemination link over standard telecommunications fiber. The system achieved a record fractional frequency instability of 2.9 × 10⁻ 21 at one day averaging time, and maintained continuous phase lock for more than four days, marking a major step toward large-scale optical clock networks and future precision timing infrastructure.

eLight•Aug 14, 2026•0 citations
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.
With the progress in the development of optical frequency standards grows the demand for the dissemination of stable optical frequencies. To date, optical fiber links constitute the most promising medium to bridge large geographical distances while still maintaining a high degree of frequency stability and accuracy. We investigated the transfer of an optical frequency along different fiber links during the past years and achieved a fractional instability and uncertainty at a level lower than 10 − 19 using fiber links with lengths of up to almost 2000 km. We give an overview of different techniques and methods that can be used in combination with optical fiber links to achieve a stable frequency transfer. The results of different fiber links are summarized and an outlook of future links is given.
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].
We realized a coherent optical fiber link in Italy, with a fiber haul of 642 km. To characterize the link, we doubled the link to 1284 km, demonstrating a characterization technique based on the double round trip on a single fiber. The link is intended to significantly improve the frequency references used in radio-astronomy and precision measurements in atomic physics. The data analysis is based on the Allan deviation, whose expression is theoretically derived from the noise power spectrum. The demonstrated resolution is 3×10−19 in 1000 s and the uncertainty of the transfer is 5×10−19. The arming of a second fiber is avoided, and this could be rather beneficial to long hauls realizations for a continental fiber network for frequency and time metrology.
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.