Time transfer is a scheme where multiple sites share a precise reference time. The technique is commonly used for creating and distributing standard time scales such as Universal Coordinated Time (UTC) and International Atomic Time (TAI). White Rabbit Precision Time Protocol (PTP-WR) is one of the best performing time transfer techniques.

Outperforming existing capabilities, providing accurate (<200 ps), resilient and secure timing traceable to Coordinated Universal Time (UTC), it is able to exploit telecommunication fibre networks, enabling its use in widespread applications, and it is now time to exploit PTP WR as an advanced service for research and industry. This project will develop the metrological capacities required to accelerate the industrial adoption of PTP-WR, through improved hardware and calibration techniques, implemented in industrial environments.

The need

There is an increasing demand for synchronisation networks that provide precise time and frequency: e.g. telecommunication operators building 5G mobile communication networks, the power-grid sector utilising smart grids, the financial sector needing to comply with EU regulations, and scientific users. International recommendations are driving improvements to current timing and UTC traceability. For example, in finance the European ‘Markets in Financial Instruments Directive’ (MiFID II), issued by the European Securities and Markets Authority, requires improved accuracy and traceability on time stamping of financial transactions from January 2018. In addition, industrial needs require solutions that are easily standardised.

PTP-WR is a technique suited for dissemination of Universal Coordinated Time UTC(k) time scales and frequency. However, whilst the calibration techniques required for PTP WR are well developed in specific, dedicated fibre links where the parameters are well known, there is still a need to develop improved scalable
calibration techniques that match different telecommunication networks.

Currently, time and frequency dissemination for most industrial applications is realised through radio signals and satellite time broadcasting, such as the widely used Global Navigation Satellite System (GNSS). However, GNSS broadcasting suffers from integrity and resilience weaknesses, since the weak power received from the satellites on Earth make spoofing, hacking and disturbance due to space weather a real threat. Techniques with higher resilience and with built in redundancy are therefore required.

The current best achievable time transfer accuracy is 2 ns – 5 ns using high quality GNSS receivers, which corresponds to a frequency resolution of 10-14 over one day measurement time, but this requires specific receivers and competences only available in national metrology institutes and very specialised scientific laboratories. Industry generally relies on less highly-performing GNSS timing equipment that is usually limited to an accuracy of 10 ns – 100 ns. The need for a more accurate and high performing technique could be addressed with PTP-WR which can strongly outperform the commonly used techniques.

One last important challenge is perhaps the most important, namely demonstrating in-field that the dissemination of Universal Coordinated Time UTC(k) time scales and frequency over optical fibres is really suited for industrial needs. Real tests in production or industrial environments are fundamental to boost the uptake by industry and other sectors.