Optical Time and Frequency Networks (OTFN)

Time and Frequency (T&F) services are critical to many civil and industrial sectors, both directly and indirectly, including telecommunications, geo-positioning (autonomous vehicles), energy, finance, and advanced scientific use cases. Access to precise time and frequency signals is, therefore, of major interest to industry, research and the economy worldwide. In the past few years, National Metrology Institutes (NMIs) have successfully developed and tested new T&F techniques using optical fibres which have shown a stability performance of at least three orders of magnitude better than the current best commercial services. Moreover, such techniques offer an alternative to Global Navigation Satellite System (GNSS) for end-users who cannot rely on broadcast signals due to, for example, security concerns such as GPS spoofing attacks or reception issues if they are located in an underground laboratory. Further, new T&F services have the potential to respond effectively to the challenges of tomorrow.

Many NRENs are now either supporting T&F services for their users, such as National Metrology Institutes (NMIs), or considering how they might do so. The work of this subtask is documenting existing practices and discussing best future practices. If you are interested in discussing OTFN further with us, please get in touch.

TF Gateway

Find information on T&F networking, services and connections in Europe.

Monitoring and Calibration

Studies of different technologies and cross-border connections.

For more information please contact us at:



Optical Time & Frequency Activities in the GÉANT Project (Past & Future)

Proceedings of the 54th Annual Precise Time and Time Interval Systems and Applications Meeting, January 23 - 26, 2023, Long Beach, California 

As optical time & frequency transfer as a service has gained interest among European providers of National Research & Education Networks (NRENs) the GÉANT network development group (Work Package 6) has put an emphasis on investigating the different options and solutions for optical T&F transfer in Europe. With more than 40 countries participating in GÉANT it is no surprise that the T&F landscape currently ranges from the deployment of ELSTAB, White Rabbit, uni- and bi-directional optical carrier, RF-over-fiber to frequency comb transfer. With such a diverse landscape of European T&F technologies and services, it is challenging to integrate these approaches into a common backbone. (pdf)

Logo for Whitepaper (Photo by Andrej Lišakov on Unsplash)

Preliminary Assessment of OC signal Transfer Quality on the Poznań-CERN Line in an Unmodified DWDM (Unidirectional) Network

GÉANT Whitepaper December 31, 2022

This white paper describes the assessment of the quality of optical frequency signal transfer in an unmodified (unidirectional) DWDM network with a range of more than 2000 km. It also covers a description of the necessary modifications to the Optical Carrier signal transfer system required to realise this type of transmission using a pair of optical fibres. (pdf)

Logo for Whitepaper (Photo by Andrej Lišakov on Unsplash)

Management and Monitoring of Time and Frequency Services

GÉANT Whitepaper October 31, 2022

This white paper describes how various European National Research and Education Networks manage and monitor production time and frequency (T&F) services implemented over optical fibres. It covers T&F transfer techniques, management areas, consistent monitoring of T&F equipment, and optical considerations for the successful operation of T&F services. (pdf)

Logo for Whitepaper (Photo by Andrej Lišakov on Unsplash)

Ultrastable Frequency Transfer in L-Band

GÉANT Whitepaper September 7, 2021

Frequency dissemination in phase-stabilised optical fibre networks for metrological frequency comparisons and precision measurements are promising candidates to overcome the limitations imposed by satellite techniques. However, in an architecture shared with telecommunication data traffic, network constraints may restrict the availability of dedicated channels in the commonly used C-band. Here, SWITCH and its partners demonstrate the dissemination of an SI-traceable ultrastable optical frequency in the L-band over a 456 km fibre network with ring topology, in which data traffic occupies the full C-band. (pdf)

Logo for Whitepaper (Photo by Andrej Lišakov on Unsplash)

Distributing New Performant Time and Frequency Services over NREN Networks

GÉANT Whitepaper August 10, 2021

This document presents the distribution of time and frequency services and existing projects in several European national research and education networks, which are members of the GÉANT 4-3 project. (pdf)

*** Infoshare ***

Time transfer calibration and measurement data exchange in multi-domain fiber optic networks

Krzysztof Turza, Wojbor Bogacki, Poznan Supercomputing and Networking Center, Poznan, Poland, IEEE IFCS - EFTF 2023, Toyama, Japan, 15-19 May 2023

European Time and Frequency Services - Principles, Challenges and Use Cases

logo of GÉANT Events Management System GÉANT Infoshare March 9, 2021

"Time & Frequency (T&F) transport as an optical service has become a hot topic for the past ten years, mainly boosted by a dramatic improvement in performance. National Metrology Institutes (NMIs) in collaboration with NRENs have demonstrated three orders of magnitude higher stability of time and frequency services than any existing commercial service over distances of at least 1,500 km, offering tremendous potential for new services in a wide range of scientific, societal and economic domains.

The Technology Readiness Level (TRL) for such T&F services is in some cases now approaching 8 (complete and qualified) or 9 (proven in operational environment), while the growth of metrological links all around the world has motivated more and more optical equipment vendors to integrate T&F features into their product portfolios. However, there is no one-fits-all solution for how to deploy  T&F services. Rather, there are multiple T&F setups (unidirectional, bidirectional, quasi-bidirectional), parts of the spectrum (S-, C-, L-Band or in between), each dictated by the distinctive needs and requirements of the networks and the end-user applications. Read more...

  • No labels