White Rabbit: Sub-nanosecond timing over Ethernet

The White Rabbit (WR) project is a multi-laboratory, multi-company effort to bring the best of the data transfer and the timing world together in a completely open design. WR is a fully deterministic Ethernet-based network for general purpose data transfer and synchronization. The aim is to enable the synchronization of a large number of nodes with sub-nanosecond accuracy and picosecond jitter over long lengths of fibre. The key technologies used are physical layer syntonization (clock recovery) and the Precision Time Protocol (IEEE 1588). WR generates sub-nanosecond synchronous precision timing in all nodes by continuous tracking and compensating the transmission delays. We give an overview of the WR project and describe the design goals and specifications of the project. The WR switch and the (user) node which are the central components of the WR system and real timing measurements of prototypes of WR hardware are presented

White Rabbit Precision Time Protocol on Long-Distance Fiber Links

The application of White Rabbit precision time protocol (WR-PTP) in long-distance optical fiber links has been investigated. WR-PTP is an implementation of PTP in synchronous Ethernet optical fiber networks, originally intended for synchronization of equipment within a range of 10 km. This paper discusses the results and limitations of two implementations of WR-PTP in the existing communication fiber networks. A 950-km WR-PTP link was realized using unidirectional paths in a fiber pair between Espoo and Kajaani, Finland. The time transfer on this link was compared (after initial calibration) against a clock comparison by GPS precise point positioning (PPP). The agreement between the two methods remained within ±2 ns over three months of measurements. Another WR-PTP implementation was realized between Delft and Amsterdam, the Netherlands, by cascading two links of 137 km each. In this case, the WR links were realized as bidirectional paths in single fibers. The measured time offset between the starting and end points of the link was within 5 ns with an uncertainty of 8 ns, mainly due to the estimated delay asymmetry caused by chromatic dispersion

Detection potential of the KM3NeT detector for high-energy neutrinos from the Fermi bubbles

<p>A recent analysis of the Fermi Large Area Telescope data provided evidence for a high-intensity emission of high-energy gamma rays with a E-2 spectrum from two large areas, spanning 50 above and below the Galactic centre (the "Fermi bubbles"). A hadronic mechanism was proposed for this gamma-ray emission making the Fermi bubbles promising source candidates of high-energy neutrino emission. In this work Monte Carlo simulations regarding the detectability of high-energy neutrinos from the Fermi bubbles with the future multi-km(3) neutrino telescope KM3NeT in the Mediterranean Sea are presented. Under the hypothesis that the gamma-ray emission is completely due to hadronic processes, the results indicate that neutrinos from the bubbles could be discovered in about one year of operation, for a neutrino spectrum with a cutoff at 100 TeV and a detector with about 6 km(3) of instrumented volume. The effect of a possible lower cutoff is also considered. (C) 2012 Elsevier B.V. All rights reserved.</p>