Momentum generated for industry and science to exploit the advantages of White Rabbit Precision Time Protocol for traceable time distribution and positioning
Demand for higher speed networking infrastructures will drive investments in more precise synchronisation of time signals.
Currently, time synchronisation is sourced from atomic clock signals distributed by satellite networks such as the US GPS network or the European Galileo network.
These signals are relatively cheap to access but the necessary signal transmission distances and weak signal strength limits accuracy and network resilience.
Optical fibre networks were proposed as suitable complementary, or supporting time distribution networks, without these drawbacks.
The EMRP project NEAT-FT demonstrated that White Rabbit Precision Time Protocol (WR-PTP), an open-source Ethernet-based protocol developed at CERN , could synchronise signals to nanosecond levels over large distances. Calibration techniques developed in the project to maintain reliable timing worked well in dedicated, high-cost, fibre links for which parameters were known. However, the method needed to be affordable for industry
This project developed improved implementation methods and traceable calibration techniques, including uncertainty evaluations for WR-PTP time transfer over shared fibre-optic networks. This work could ensure multiple sites can share accurate reference time, suitable for distributing reference time scales such as national realisations of Coordinated Universal Time (UTC).
Training in the calibration method was provided to fibre network provider Tallgrass and the networking hardware and service provider OPNT. As a result, OPNT established a calibrated network for time and frequency, validated by loop-back connections and shown to be accurate within 1 ns. The calibration procedure was documented as a best practice guide.
The knowledge and techniques developed in this project were applied in two demonstrator projects supported by VSL and OPNT.
First, the potential for WR-PTP to support upgraded Galileo services was confirmed by the Triple-T demonstrator project, managed by the European Space Research and Technology Centre (ESTEC). This six-month trial distributed Galileo timing signals over a 260 km fibre link. The timing service remained available for 95% of the trial and varied by no more than 0.2 nanoseconds.
Similarly, in September 2020 the Delft University of Technology SuperGPS project provided the first experimental demonstration of a fibre-based terrestrial positioning system. Sited at The Green Village in Delft, the demonstrator was calibrated by VSL to sub-nanosecond levels, providing positioning in the low-decimetre range.
The EMPIR project WRiTE builds on the work done in this project by focussing on industrial exploitation, standardisation, and improved performance of traceable timing and positioning.