White Rabbit Technology Research Articles

Reliability studies for the White Rabbit Switch in KM3NeT: FIDES and Highly Accelerated Life Tests

Two neutrino telescopes are being installed in the Mediterranean Sea by the KM3NeT Collaboration. The Collaboration is currently validating the viability of the standard White Rabbit technology for the next phase of the project. One of the necessary studies for this validation is the reliability assessment of the Switching Core Board and its carrier, the main electronics components of the White Rabbit Switch. This contribution presents the reliability studies, based on the FIDES method, performed to the Switch Core Board and the KM3NeT carrier in order to obtain an estimate of the Failure In Time, as well as to find which components can be optimised in order to increase the reliability of the system. Moreover, the Highly Accelerated Life Tests, a stress testing methodology for enhancing product reliability, performed to the first prototypes of the switch electronics boards, produced with the FIDES modifications, are presented.

The White Rabbit Time Synchronization Protocol for Synchrophasor Networks

Within the context of time dissemination techniques for power systems applications, this paper discusses the use of the white rabbit (WR) protocol for synchrophasor networks. Specifically, this paper presents a phasor measurement unit (PMU) integrating the WR technology and its experimental validation with a focus on the synchrophasor phase estimation in steady state conditions, by using a PMU calibrator generating the reference signals. We further compare the accuracy of the developed PMU with other state-of-the-art time synchronization technologies for PMUs, i.e., global positioning system (GPS) and precision time protocol (PTP), demonstrating applicability of WR for PMU sensing networks.

Compact Distributed Digitizers With Metrological Precision

Prototype distributed digitizers have been developed with the metrological precision of the individual measurement nodes. A master controller aggregates the data of the nodes and performs all computational tasks. A crucial part of the system is the synchronization of the individual nodes at the nanosecond level using white-rabbit technology. Fiber-optic communication is used to reduce interference and to obtain high isolation. When operated on battery power, this allows for special applications such as the measurement of currents in high-voltage lines. First, results show that a phase difference between nodes of a few microradians can be achieved with a resolution of better than $0.1~\mu $ rad.

A Fully Programmable White-Rabbit Node for the SKA Telescope PPS Distribution System

Distributed data acquisition (DAQ) systems are in charge of converting different analog environment signals into digital values to perform control and monitor tasks. They require a computer network technology to share data between their different elements. One of their main issues is to match data with the specific events under study. A possible solution is to include an event synchronization technology such as Network Time Protocol (NTP), Precise Time Protocol (PTP), or White Rabbit (WR). This contribution proposes a high-performance distributed timing system based on the WR technology. We focus on the square kilometer array (SKA) project as an example of the distributed DAQ system. The SKA project has a strict timing requirements for its operation with a performance below 2 ns. This accuracy is not achievable by current standard synchronization technologies such as NTP or PTP. Under this context, the authors propose the WR zynq embedded node (WR-ZEN) platform as a candidate for the SKA’s pulse per second (PPS) distribution system. It is a new design that integrates the WR technology, thus enabling the subnanosecond accuracy. Finally, the WR-ZEN has been evaluated in different scenarios to demonstrate its timing performance in dynamic environment conditions fulfilling the SKA telescope requirements for PPS distribution.

The new CLBv4 for the KM3NeT Neutrino Telescope

The KM3NeT collaboration aims at the construction of a deepsea neutrino observatory in the Mediterranean Sea equipped with thousands of glass spheres, the so-called Digital Optical Modules, each of which contains 31 photomultipliers of small photocathode area. These devices will be used for the detection of the Cherenkov light induced by charged particles produced by the interaction of neutrinos with matter inside or in the vicinity of the KM3NeT detector. The signal acquired by each photomultiplier is sent to a Time to Digital Converter which is part of a Central Logic Board. The Time to Digital Converter resolution is 1 ns and the White Rabbit technology is used to guarantee time synchronization between the optical modules. Due to the large volume to be instrumented by KM3NeT, a cost reduction of the different systems is important so different versions of the Central Logic Board have been designed. The newest version was designed also to also reduce the phase noise in the main clock, to improve the stability of the synchronization.

White Rabbit HSR: A Seamless Subnanosecond Redundant Timing System With Low-Latency Data Capabilities for the Smart Grid

New smart grid and industrial-Internet-of-things (IIoT) directions require accurate synchronization features to capture, trigger, and manage events in industrial networks with the best possible precision and accuracy. The implementation of redundancy features for time and data distribution to increase fault tolerance, together with an enhancement of the availability of the network services such as generic object-oriented substation events, become mandatory due to their critical nature. For these reasons, the authors of this paper presented a new challenging approach covering the industrial standards requirements regarding timing and availability through the development of mechanisms that make possible the avoidance of single point of failure in ring topologies. This approach uses the White Rabbit (WR) as the main timing distribution technology, able to synchronize devices below 1 ns. Moreover, the development of a mechanism able to change from a primary to a backup time reference in approximately zero time with an observed maximum phase shift of 170 ps implies an important qualitative leap with respect to IIoT and the smart grid (e.g., phasor measurement units). This paper addresses the development and results of the high-availability seamless redundancy protocol for the WR technology to conform a leading-edge deterministic and reliable ultraaccurate timing system with high-availability data features for industrial facilities in accordance with IEC 61850 and IEC 62439-3.

The integration of FPGA TDC inside White Rabbit node

White Rabbit technology is capable of delivering sub-nanosecond accuracy and picosecond precision of synchronization and normal data packets over the fiber network. Carry chain structure in FPGA is a popular way to build TDC and tens of picosecond RMS resolution has been achieved. The integration of WR technology with FPGA TDC can enhance and simplify the TDC in many aspects that includes providing a low jitter clock for TDC, a synchronized absolute UTC/TAI timestamp for coarse counter, a fancy way to calibrate the carry chain DNL and an easy to use Ethernet link for data and control information transmit. This paper presents a FPGA TDC implemented inside a normal White Rabbit node with sub-nanosecond measurement precision. The measured standard deviation reaches 50ps between two distributed TDCs. Possible applications of this distributed TDC are also discussed.

Using single wavelength light to improve the synchronization accuracy of the White Rabbit system

We demonstrate a new synchronization method for the White Rabbit system. Signals are transmitted in a single mode fiber in both directions with the same light wavelength. Without the complex calibration process of the fiber asymmetry parameter, the new method reduces the effect of chromatic dispersion and improves the synchronization accuracy. The experiment achieves timing synchronization accuracy below 200 ps over 50 km fiber constructed by different companies’ fiber spools. The proposed method would make White Rabbit technology immune to the chromatic dispersion of fiber links and can be applied to long distance synchronization.

Timing calibration and directional reconstruction for Tunka-HiSCORE

The Tunka-HiSCORE detector follows the concept of a non-imaging wide-angle EAS Cherenkov array, designed to search for γ-ray sources above 10 TeV and to investigate the spectrum and composition of cosmic-rays above 100 TeV. A prototype array with 9 stations has been deployed in October 2013 at the site of the Tunka experiment in Russia. We describe design and performance of the array data acquisition system DAQ-2, focusing on its timing system based on the White Rabbit technology for sub-nsec time-synchronization over ethernet. First results of EAS arrival direction reconstruction, compared with MC simulations, and tests with artifical light sources verify an excellent performance of the system.

High resolution distributed time-to-digital converter (TDC) in a White Rabbit network

The Large High Altitude Air Shower Observatory (LHAASO) project consists of a complex detector array with over 6000 detector nodes spreading over 1.2km2 areas. The arrival times of shower particles are captured by time-to-digital converters (TDCs) in the detectors' frontend electronics, the arrival direction of the high energy cosmic ray are then to be reconstructed from the space-time information of all detector nodes. To guarantee the angular resolution of 0.5°, a time synchronization of 500ps (RMS) accuracy and 100ps precision must be achieved among all TDC nodes. A technology enhancing Gigabit Ethernet, called the White Rabbit (WR), has shown the capability of delivering sub-nanosecond accuracy and picoseconds precision of synchronization over the standard data packet transfer. In this paper we demonstrate a distributed TDC prototype system combining the FPGA based TDC and the WR technology. With the time synchronization and data transfer services from a compact WR node, separate FPGA-TDC nodes can be combined to provide uniform time measurement information for correlated events. The design detail and test performance will be described in the paper.