Time and Frequency Transfer via White Rabbit
White Rabbit, developed at CERN, is a time distribution protocol based on Ethernet. It is currently being developed as part of an international collaboration with a community of over 50 active developers.
White Rabbit relies on the distribution of an ultra-stable time reference and a radiofrequency (typically 10 MHz) within the local network. It is possible to achieve precision on the order of nanoseconds, particularly for high-performance synchronization applications.
We are building a national White Rabbit network to distribute these two signals (time reference and radiofrequency) in addition to the ultra-stable optical frequency. The goal is to implement a set of White Rabbit Switches (WRS) that will disseminate the UTC(OP) frequency and time to different nodes of the network. UTC(OP) is the time scale reference for France and the basis of French legal time. This new service will support and facilitate the use of the REFIMEVE optical signal by end users, complement the service portfolio of REFIMEVE, and prepare its integration into the European research infrastructure landscape. The White Rabbit Switch network will also be a key point for monitoring the REFIMEVE network itself, as it will enable the distribution of an RF reference to each node of the network. Such an RF reference is essential for characterizing residual instabilities in the links originating from the nodes, ensuring the supervision of the metrological network.
The set formed by the three ultra-stable signals distributed over the REFIMEVE network – time reference, radiofrequency, and optical frequency – will ultimately constitute a unique infrastructure worldwide.
In practice, the White Rabbit Switches come from CERN, where years of R&D on the subject have been conducted, ensuring the compatibility of future developments (see photo). The equipment and its specifications (hardware and software) therefore depend not on manufacturers but on the White Rabbit collaboration. All the detailed technical specifications are documented on the White Rabbit project wiki at CERN:
Example of a WRS 3/18 switch (Safran)