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papers/ISPCS2018/wrApplicationsOverview.bib
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......@@ -15,7 +15,7 @@ doi={10.1109/IEEESTD.2014.6991462},}
@online{biblio:allan90,
author = {D.B. Sullivan and D.W. Allan and D.A. Howe and F.L. Walls},
title = {{Characterization of Clocks and Oscillators}},
url = {http://tf.nist.gov/general/pdf/868.pdf},
url = {tf.nist.gov/general/pdf/868.pdf},
note = "{NIST Technical Note 1337}",
urldate = {1990},
}
......@@ -86,7 +86,7 @@ year={2018},
@online{biblio:CERN,
title = {{European Organization for Nuclear Research (CERN)}},
url = {www.cern.ch/},
howpublished = {\url{https://www.cern.ch/}},
howpublished = {\url{www.cern.ch/}},
abstract = {{CERN}, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works.},
urldate = {2014-06-17},
keywords = {{CERN}, high-energy physics, Large Hadron Collider, {LHC}, particles, physics, science},
......@@ -104,7 +104,7 @@ year={2018},
note={CERN Presentation},
year=2008,
file = {CERN-GMT.pdf:/home/mlipinsk/.mozilla/firefox/64taeemp.default-1397950810482/zotero/storage/F3RGN3RC/CERN-GMT.pdf:application/pdf},
howpublished = {\url{https://indico.cern.ch/event/28233/contribution/1/material/slides/1.pdf}},
howpublished = {\url{indico.cern.ch/event/28233/contribution/1/material/slides/1.pdf}},
}
@Inproceedings{P1588-HA-enhancements,
author={O. Ronen and M. Lipinski},
......@@ -113,23 +113,23 @@ title={Enhanced synchronization accuracy in IEEE1588},
}
@electronic{biblio:fmc-dio-5cha,
title = "{FMC 5-channel Digital I/O module}",
howpublished = {\url{https://www.ohwr.org/projects/fmc-dio-5chttla/wiki/wiki}}
howpublished = {\url{www.ohwr.org/projects/fmc-dio-5chttla/wiki/wiki}}
}
@electronic{biblio:fmc-dio-del,
title = "{MC DEL 1ns 4cha delay module }",
howpublished = {\url{https://www.ohwr.org/projects/fmc-delay-1ns-8cha/wiki/wiki}}
howpublished = {\url{www.ohwr.org/projects/fmc-delay-1ns-8cha/wiki/wiki}}
}
@electronic{biblio:fmc-tdc-5cha,
title = "{FMC TDC 1ns 5cha}",
howpublished = {\url{https://www.ohwr.org/projects/fmc-tdc/wiki/wiki}}
howpublished = {\url{www.ohwr.org/projects/fmc-tdc/wiki/wiki}}
}
@misc{biblio:WR@LIST,
title = {{LHC} {Instabilities} {Trigger} {Distribution}},
url = {https://indico.cern.ch/event/295937/contribution/1/material/slides/0.pdf},
author = {T. Wlostowski},
note="{CERN Presentation}",
howpublished = {\url{https://indico.cern.ch/event/295937/contribution/1/material/slides/0.pdf}},
howpublished = {\url{indico.cern.ch/event/295937/contribution/1/material/slides/0.pdf}},
date ="2014"
}
......@@ -142,13 +142,13 @@ year = "2015",
@inproceedings{biblio:WR-LIST-2,
author = "T.Levens and et al.",
title = "INSTABILITY DIAGNOSTICS",
booktitle = "{6th Evian Workshop}",
booktitle = "{Evian Workshop}",
year = "2015",
}
@electronic{biblio:wr-streamers,
title = "{White Rabbit Streamers IP Core}",
howpublished = {\url{https://www.ohwr.org/projects/wr-cores/wiki/wr-streamers}}
howpublished = {\url{www.ohwr.org/projects/wr-cores/wiki/wr-streamers}}
}
@INPROCEEDINGS{biblio:wr-cngs,
author={M. Lipinski and et al.},
......@@ -171,7 +171,7 @@ year={2012},
}
@Misc{biblio:WR-Btrain,
title = "{{BTrain} over White Rabbit}",
howpublished = "{\url{https://gitlab.cern.ch/BTrain-TEAM/Btrain-over-WhiteRabbit/wikis/home}}"
howpublished = "{\url{gitlab.cern.ch/BTrain-TEAM/Btrain-over-WhiteRabbit/wikis/home}}"
}
@Misc{biblio:WR-Btrain-status,
author = "Maciej Lipinski",
......@@ -185,13 +185,12 @@ year = "2015",
}
@techreport{biblio:FAIRtimingSystem,
@Misc{biblio:FAIRtimingSystem,
author = "T. Fleck and et al.",
title = "{FAIR Timing System}",
institution = "GSI",
address = "Darmstadt, Germany",
year = "2009",
note = "v1.2",
}
......@@ -200,7 +199,7 @@ author = "C.Prados and et al.",
title = "{A Reliable White Rabbit Network for the FAIR General Machine Timing}",
booktitle = "{ICALEPCS}",
year = "2017",
howpublished = "{\url{http://accelconf.web.cern.ch/AccelConf/icalepcs2017/papers/tupha091.pdf}}"
howpublished = "{\url{accelconf.web.cern.ch/AccelConf/icalepcs2017/papers/tupha091.pdf}}"
}
@thesis{biblio:MathiasPhD,
......@@ -208,7 +207,7 @@ howpublished = "{\url{http://accelconf.web.cern.ch/AccelConf/icalepcs2017/paper
title = "{On Time, in Style: Nanosecond Accuracy in Network Control Systems}",
year = "2017",
school = "University of Wales",
howpublished = "{\url{https://www-acc.gsi.de/wiki/pub/Timing/TimingSystemDocuments/kreiderPhdwiki.pdf}}"
howpublished = "{\url{www-acc.gsi.de/wiki/pub/Timing/TimingSystemDocuments/kreiderPhdwiki.pdf}}"
}
@Misc{biblio:GSI-schedule,
title = "{GSI - General Plan of Accelerator Operation 2018}",
......@@ -268,11 +267,11 @@ howpublished = "{\url{http://accelconf.web.cern.ch/AccelConf/icalepcs2017/paper
@Misc{biblio:WR-LJD,
title = "{WRS Low Jitter Daugherboard}",
howpublished = {\url{https://www.ohwr.org/projects/wrs-low-jitter/wiki/wiki}},
howpublished = {\url{www.ohwr.org/projects/wrs-low-jitter/wiki/wiki}},
}
@ARTICLE{biblio:MIKES+VSL,
author={E. F. Dierikx and et al.},
journal={IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control},
journal={IEEE T-UFFC},
title={White Rabbit Precision Time Protocol on Long-Distance Fiber Links},
year={2016},
volume={63},
......@@ -319,7 +318,7 @@ month={July},}
@inproceedings{biblio:WR-ultimate-limits,
author = "Rizzi, Mattia and et al.",
title = "{White Rabbit clock synchronization: ultimate limits on close-in phase noise and short-term stability due to FPGA implementation}",
booktitle = "{Transactions on Ultrasonics, Ferroelectrics, and Frequency Control}",
booktitle = "{IEEE T-UFFC}",
year = "2018",
}
@Misc{biblio:WR-LJD-switch,
......@@ -328,7 +327,7 @@ year = "2018",
}
@Misc{biblio:optical-amplifier,
title = "OPNT's quasi bidirectional optical amplifiers",
howpublished = {\url{http://www.opnt.nl/\#timing}},
howpublished = {\url{www.opnt.nl/\#timing}},
}
@inproceedings{biblio:WR-NIST,
author = "J. Savory and et al.",
......@@ -338,7 +337,7 @@ year = "2018",
}
@Misc{biblio:wr-sfps,
title = " SFP transceiver and fibre type to use for White Rabbit",
howpublished = {\url{https://www.ohwr.org/projects/white-rabbit/wiki/SFP}},
howpublished = {\url{www.ohwr.org/projects/white-rabbit/wiki/SFP}},
}
@inproceedings{biblio:WR-INRIM,
author = "G. Fantino and et al.",
......@@ -348,7 +347,7 @@ year = "2014",
}
@Misc{biblio:WR-INRIM-400km,
title = "WR-based time transfer between INRIM and Milano",
howpublished = {\url{https://www.top-ix.org/en/2018/03/22/the-time-as-service-service-becomes-operational/}},
howpublished = {\url{www.top-ix.org/en/2018/03/22/the-time-as-service-service-becomes-operational/}},
}
@inproceedings{biblio:GSI-WR-GMT,
......@@ -360,7 +359,7 @@ year = "2018",
@Misc{biblio:GSI-WR-GMT-wiki,
title = "WR-based General Machine Timing System at GSI",
howpublished = {\url{https://www-acc.gsi.de/wiki/Timing/TimingSystemDocuments}},
howpublished = {\url{www-acc.gsi.de/wiki/Timing/TimingSystemDocuments}},
}
@inproceedings{biblio:GSI-WR-GMT-CRYRING,
author = "M.Kreider and et al.",
......@@ -376,13 +375,13 @@ year = "2018",
@Inproceedings{biblio:LHAASO-WR-temp,
author = "Hongming Li and et al.",
title = "{Temperature Effect and Correction Method of White Rabbit Timing Link}",
booktitle = "IEEE TRANSACTIONS ON NUCLEAR SCIENCE, JUNE 2015",
booktitle = "IEEE Transactions on Nuclear Science",
year = "2015",
}
@Inproceedings{biblio:LHAASO-WR-calibrator,
author = "Hongming Li and et al.",
author = "Hongming Li and Guanghua Gong and Jianmin Li",
title = "{Portable Calibration Node for LHAASO-KM2A Detector Array}",
booktitle = "IEEE TRANSACTIONS ON NUCLEAR SCIENCE,JUNE 2017",
booktitle = "IEEE Transactions on Nuclear Science",
year = "2017",
}
@Inproceedings{biblio:LHAASO-WR-prototype,
......@@ -393,7 +392,7 @@ year = "2018",
}
@misc{biblio:KM3NeT,
title = "{The Cubic Kilometre Neutrino Telescope (KM3NeT)}",
howpublished = {\url{http://km3net.org}},
howpublished = {\url{km3net.org}},
}
@Misc{biblio:WR-KM3NeT-Letter,
title = "KM3NeT 2.0: Letter of Intent for ARCA and ORCA",
......@@ -401,17 +400,17 @@ year = "2018",
}
@Misc{biblio:WR-KM3NeT-presentation,
title = "{White Rabbit in KM3NeT}",
howpublished = {\url{www.ohwr.org/attachments/4263/6\_wr\_km3net\_15032016.pptx}},
howpublished = {\url{www.ohwr.org/attachments/4263/ 6\_wr\_km3net\_15032016.pptx}},
}
@Misc{biblio:SKA,
title = "Square Kilometre Array ",
howpublished = {\url{https://www.skatelescope.org}},
howpublished = {\url{www.skatelescope.org}},
}
@Misc{biblio:ELI-ALP-WR,
title = "{ELI-ALPS: Synchronization issues}",
howpublished = {\url{www.ohwr.org/attachments/3565/WR\_WS\_GENEVA\_6OCT2014\_IK\_ELI\_ALPS.pptx}},
howpublished = {\url{www.ohwr.org/attachments/3565/ WR\_WS\_GENEVA\_6OCT2014\_IK\_ELI\_ALPS.pptx}},
}
@Misc{biblio:ELI-BEAMS-WR,
title = "{ELI-BEAMS: Electronic Timing System at Facility Level}",
......@@ -448,8 +447,8 @@ month={Sept},}
year = "2003",
}
@Misc{biblio:WRXI,
title = "White Rabbit eXtensions for Instrumentation",
howpublished = {\url{https://www.ohwr.org/projects/wrxi/wiki/wiki}},
title = "{WRXI}",
howpublished = {\url{www.ohwr.org/projects/wrxi/wiki/wiki}},
}
@Inproceedings{biblio:CSNS-WR,
author = "Jian Zhuang and et al.",
......@@ -459,25 +458,25 @@ month={Sept},}
}
@Misc{biblio:JINR,
title = "The Joint Institute for Nuclear Research ",
howpublished = {\url{http://www.jinr.ru/main-en/}},
howpublished = {\url{www.jinr.ru/main-en/}},
}
@Misc{biblio:JINR-WR,
title = "JINR AFI Electronics",
howpublished = {\url{http://afi.jinr.ru/CategoryWhiteRabbit}},
title = "{JINR AFI} Electronics",
howpublished = {\url{afi.jinr.ru/CategoryWhiteRabbit}},
}
@Misc{biblio:ESRF,
title = "European Synchrotron Radiation Facility",
howpublished = {\url{http://www.esrf.eu/about}},
howpublished = {\url{www.esrf.eu/about}},
}
@Inproceedings{biblio:ESRF-WR,
author = "G.Goujon and et al.",
title = "REFURBISHMENT OF THE ESRF ACCELERATOR SYNCHRONISATION SYSTEM USING {W}HITE {R}ABBIT",
title = "REFURBISHMENT OF THE {ESRF} ACCELERATOR SYNCHRONISATION SYSTEM USING {W}HITE {R}ABBIT",
booktitle = "ICALEPCS",
year = "2017",
}
@online{biblio:wrCalibration,
title = "{White Rabbit calibration procedure}",
url = {http://www.ohwr.org/documents/213},
title = "{WR calibration procedure}",
howpublished = {\url{www.ohwr.org/documents/213}},
author = {G. Daniluk},
urldate = {August 13, 2014},
}
......@@ -488,8 +487,8 @@ booktitle = "{ISPCS}",
year = "2016",
}
@Misc{biblio:SPS-WR-LLRF,
title = "MicroTCA Low-level RF White Rabbit Node",
howpublished = {\url{https://www.ohwr.org/projects/ertm15-llrf-wr/wiki}},
title = "{MicroTCA Low-level RF WR Node}",
howpublished = {\url{www.ohwr.org/projects/ertm15-llrf-wr/wiki}},
}
@Inproceedings{biblio:SKA-80km,
author = "Paul Boven",
......@@ -499,19 +498,19 @@ year = "2016",
}
@Misc{biblio:WR-calibration,
title = "White Rabbit Calibration",
howpublished = {\url{https://www.ohwr.org/projects/wr-calibration/wiki/wiki}},
title = "{WR} Calibration",
howpublished = {\url{www.ohwr.org/projects/wr-calibration/wiki/wiki}},
}
@Misc{biblio:P1588,
title = "p1588 Working Group",
howpublished = {\url{https://ieee-sa.imeetcentral.com/1588public/}},
title = "P1588 Working Group",
howpublished = {\url{ieee-sa.imeetcentral.com/1588public/}},
}
@Misc{biblio:WRin1588,
title = "{White Rabbit integration into IEEE15880-20XX as High Accuracy}",
howpublished = {\url{www.ohwr.org/projects/wr-std/wiki/wrin1588}},
}
@Misc{biblio:WRusers,
title = "{White Rabbit Users}",
title = "{WR Users}",
howpublished = {\url{www.ohwr.org/projects/white-rabbit/wiki/WRUsers}},
}
@Misc{biblio:WRcompanies,
......@@ -519,12 +518,12 @@ year = "2016",
howpublished = {\url{www.ohwr.org/projects/white-rabbit/wiki/wrcompanies}},
}
@Misc{biblio:TAIGA-WR-harsh-env,
title = "{TESTING {W}HITE {R}ABBIT HARDWARE IN FIELD CONDITIONS IN SIBERIA}",
title = "TESTING {W}HITE {R}ABBIT HARDWARE IN FIELD CONDITIONS IN SIBERIA",
howpublished = {\url{www.asterics2020.eu/article/testing-white-rabbit-hardware-field-conditions-siberia}},
}
@Misc{biblio:GVD,
title = "{Baikal Neutrino Observatory}",
howpublished = {\url{http://www.inr.ru/eng/ebgnt.html}},
howpublished = {\url{www.inr.ru/eng/ebgnt.html}},
}
@Inproceedings{biblio:TAIGA-WR-1,
author = "M. Bruckner and et al.",
......@@ -542,3 +541,15 @@ year = "2016",
title = "{{HAWC} and “{HAWC-S}outh”}",
howpublished = {\url{www.iaps.inaf.it/stacex/Presentazioni/DuVernois\_Stacex.pdf}},
}
@Misc{biblio:GM-Meinberg,
title = "{Meinberg LANTIME M1000-IMS /10003285}",
}
@Inproceedings{biblio:VLS-WR-insite-calib,
author = "J.C.J. Koelemeij",
title = "{Sub-nanosecond time distribution through long-haul fiber-optic links using White Rabbit Ethernet}",
booktitle = "PTTI",
year = "2017",
}
@Misc{biblio:WRITE,
title = "{{WRITE}: White Rabbit Industrial Timing Enhancement (SRT-i26: Selected Research Topic, was JRP-i26)}",
}
papers/ISPCS2018/wrApplicationsOverview.tex
View file @ defca665
......@@ -37,41 +37,42 @@
\title{White Rabbit Applications and Enhancements}
\title{White Rabbit Applications and Enhancements\vspace{-0.4cm}}
\author{
\IEEEauthorblockN{M. Lipi\'{n}ski, E. van der Bij, J. Serrano, T. Wlostowski, G. Daniluk, A. Wujek, M. Rizzi, D. Lampridis}
\IEEEauthorblockA{CERN, Geneva, Switzerland}
\IEEEauthorblockA{CERN, Geneva, Switzerland\vspace{-0.55cm}}
}
\begin{document}
\maketitle
\begin{abstract}
%\boldmath
This article provides an overview of applications and
enhancements to the White Rabbit (WR) extension of the Precision Time Protocol (PTP).
Initially developed to serve accelerators at the European Organization for
Nuclear Research (CERN), WR has become widely-used synchronization solution
in scientific installations. This article classifies WR applications
into five types, briefly explains each and describes its example
installations. It then summarizes WR enhancements that have been triggered by
such proliferation of applications and WR's integration into the PTP.
With its wide adaptation in science, commercial support,
up-coming standardization and EU-founded projects to catalyze applications in the
industry, we can conclude that WR applications will continue to proliferate, both
in science and industry.
installations. It summarizes WR enhancements that have been triggered by
different applications and outlines WR's integration into the PTP standard.
Finally, it concludes that WR applications will continue to proliferate in
science and should soon find its way into the industry.
\end{abstract}
\end{abstract}
\vspace{-0.4cm}
\section{Introduction}
White Rabbit (WR) \cite{biblio:whiteRabbit} is a new technology that provides sub-nanosecond
accuracy and picoseconds precision of synchronization as well as deterministic and
reliable data delivery for large distributed systems. The project with the same name
is a multilaboratory, multicompany and multinational collaboration that was originally set up to
develop a versatile solution for control and data acquisition
systems.
reliable data delivery for large distributed systems.
% \textcolor{gray}{
% The project with the same name
% is a multilaboratory, multicompany and multinational collaboration that was originally set up to
% develop a versatile solution for control and data acquisition
% systems.}
% White Rabbit (WR) \cite{biblio:whiteRabbit} is a
% multilaboratory, multicompany and multinational collaboration to
......@@ -86,7 +87,7 @@ to meet the requirements of WR applications. A WR network
% , depicted in Figure~\ref{fig:WRN},
is a Bridged Local Area Network (IEEE 802.1Q) that uses Ethernet
(IEEE 802.3) to interconnect network elements and
Precision Time Protocol (PTP, IEEE 1588-2008) to synchronize
Precision Time Protocol (PTP, IEEE 1588) to synchronize
them. A WR network consists of WR switches and WR nodes
that implement WR enhancements:
\begin{enumerate}
......@@ -109,11 +110,12 @@ manner ensuring at most a single failure per year for a network of 2000 WR nodes
% \end{figure}
Since its conception in 2008, the number of WR applications has grown beyond
any expectations \cite{biblio:WRusers}. The reasons for such a proliferation of applications
any expectations. The WR Users \cite{biblio:WRusers} website attempts to keep
track of WR applications. The reasons for such a proliferation of applications
are the open nature of the WR project and the fact that the WR technology is based
on well-known and well-established standards. The former encourages collaboration,
on standards. The former encourages collaboration,
reuse of work and adaptations that also prevent vendor lock-in. The latter allows using
off-the-shelf solutions (hardware/software) with WR networks and catalyzes
off-the-shelf solutions with WR networks and catalyzes
collaboration with companies.
% What started as a project to renovate one of the most critical systems at CERN,
......@@ -125,13 +127,12 @@ collaboration with companies.
% This article attempts at providing a snapshot of the various WR applications,
% the ongoing work on enhancing WR and evolution of WR into IEEE1588.
The article briefly describes in Section~\ref{sec:wrElements} the portfolio of
readily available WR network elements. It then explains in
available WR network elements. It then explains in
Sections~\ref{sec:time-and-freq}-\ref{sec:RFoverWR} different types of
WR applications, their concept and use examples,
summarized in Table~\ref{tab:applications}. Some of the described applications
require enhancements of WR performance. These enhancements are described in
summarized in Table~\ref{tab:applications}. Application-triggered enhancements are described in
Section~\ref{sec:WRenhancements}. Finally, in Section~\ref{sec:WRin1588} we
briefly describe the about-to-complete integration of WR in the upcoming revision of the
briefly describe the integration of WR into the
IEEE1588 standard and we conclude in Section~\ref{sec:conclusions}.
\begin{table}[!t]
\caption{Non-exhaustive list of White Rabbit applications}
......@@ -175,7 +176,7 @@ GVD & Russia & TS,TD & 1km & 3/1/1
LHAASO & China & TF,TS & 1km & 40/4/4 & 6734/564/4 & \cite{biblio:LHAASO}\cite{biblio:LHAASO-WR-temp}\cite{biblio:LHAASO-WR-calibrator} \cite{biblio:LHAASO-WR-prototype}\\ \hline
% HiSCORE & Russia & TS,TD & & & & \\ \hline
TAIGA & Russia & TS,TD & 1km & 20/4/2 & 1100/90/3 & \cite{biblio:TAIGA-WR-1}\cite{biblio:TAIGA-WR-2} \\ \hline
TAIGA & Russia & TS,TD & 1km & 20/4/2 & 1100/90/3 & \cite{biblio:TAIGA-WR-1}\cite{biblio:TAIGA-WR-2}\cite{biblio:TAIGA-WR-harsh-env} \\ \hline
CTA & Spain/Chile & TF,TS & 10km & 32/3/2 & 220/10/2 & \cite{biblio:CTA-WR-timestamps}\\ \hline
......@@ -201,7 +202,7 @@ EPFL & Switzerland & TS & 1km & 2/1/1
\multicolumn{4}{|r|}{\textbf{Total number of WR nodes: }} & \textbf{339} & \textbf{13901} & \\
\multicolumn{4}{|r|}{\textbf{Total number of WR switches: }} & \textbf{53} & \textbf{641} & \\ \hline
\multicolumn{7}{|l|}{\textbf{Abbreviations used}} \\
% \multicolumn{7}{|l|}{\textbf{Abbreviations used}} \\
\multicolumn{7}{|l|}{TF= time and frequency transfer, TC= time-triggered control, TS= timestamping,} \\
\multicolumn{7}{|l|}{TD= trigger distribution, FL= Fixed-latency data transfer, RF= Radio-Freq. transfer} \\
\multicolumn{7}{|l|}{N= number of WR nodes, S= number of WR switches, L= number of layers} \\ \hline
......@@ -236,11 +237,11 @@ AMC \cite{biblio:AFC}\cite{biblio:AFCK},
FMC \cite{biblio:cute-wr-dp},
cRIO \cite{biblio:crio} and
PXI \cite{biblio:spexi}.
All of these boards are commercially available \cite{biblio:WRcompanies}.
Morover, more and more companies integrate WR into their products,
All of these boards are open and commercially available \cite{biblio:WRcompanies}.
Morover, more and more companies integrate WR into their proprietary products,
\cite{biblio:STRUCK}\cite{biblio:sundance}\cite{biblio:spdevices}.
Such a variety of WR nodes facilitaties
implementations of WR applications as described in the following sections
implementations of WR applications described in the following sections.
% \begin{figure}[!ht]
......@@ -269,53 +270,42 @@ implementations of WR applications as described in the following sections
\section{Time and Frequency Transfer (TF)}
\label{sec:time-and-freq}
\subsection{Basic Concept}
% \subsection{Basic Concept}
The most basic application of WR is the transfer of time and frequency from the
Grandmaster WR switch/node (Grandmaster) to all other WR switches/nodes in
the WR network. WR ensures that the Pulse Per Second (PPS) outputs of all the
WR switches/nodes in the WR network are aligned to the PPS output of the
Grandmaster with a sub-ns accuracy and picoseconds precision. WR switches and
nodes use and can a output clock signal (e.g. 10MHz, 125MHz) that is traceable to that
nodes use and can output a clock signal (e.g. 10MHz, 125MHz) that is traceable to that
of the Grandmaster.
In most applications, the Grandmaster is connected to a clock reference. Typically,
this is a Cesium or Rubidium oscillator disciplined by a global
navigation satellite system (GNSS).
navigation satellite system (GNSS) \cite{biblio:PolaRx4e}\cite{biblio:CS4000}\cite{biblio:GM-Meinberg}.
In such case, the time and frequency transferred by WR are traceable to
the International Atomic Time (TAI).
Although all of WR applications are based on precise transfer of time and
frequency, most of these applications benefit from functionalities that are
built on top of it and described in the subsequent sections.
% Although all of WR applications are based on precise transfer of time and
% frequency, most of these applications benefit from functionalities that are
% built on top of it and described in the subsequent sections.
% For example, the
% precise timestamping functionality (Section~\ref{sec:timestamping}) can be
% either integrated into WR nodes or provided by external devices (e.g. digitizers)
% synchronized using PPS \& 10MHz provided by WR.
\subsection{Example Applications}
% \subsection{Example Applications}
Time and frequency transfer is used by National Time Laboratories to
disseminate the official UTC time and to compare clocks. Laboratories in
Finland (VTT MIKES), Netherlands (VSL), France (LNE-SYRTE), UK (NLP),
USA (NIST) and Italy (INRIM) have WR installations. MIKES and INRIM
use WR to provide their realization of UTC to clients, e.g. UTC(MIKE) over a 50~km
link to the Metsähovi Observatory \cite{biblio:MIKES-50km} for applications in geodesy,
% (International GNSS Service,
% Very-long-baseline interferometry and satellite laser ranging)
UTC(INRIM) over
400~km to the financial district of Millano. NIST and LNE-SYRTE use WR to distribute
within their campus UTC(NIST) and UTC(OP), respectively. All
laboratories are studying WR with different types and lengths of fiber links and attempt to
increase its performance. These studies showed that the stability (at tau=1s) of the off-the-shelf
WR switch is 1e-11 (Alan Deviation, ADEV, similar to a typical frequency counter e.g. Keysight 53230A)
and can be improved. This prompted the development of the Low-Jitter Daughterboard
\cite{biblio:WR-LJD} that improves the performance of the WR switch to 1e-12 without any
modifications to the WR-PTP Protocol, see
\cite{biblio:MIKES-50km}\cite{biblio:SYRTE-LNE-500km}\cite{biblio:WR-ultimate-limits}.
The improved WR Switches are now commercially available \cite{biblio:WR-LJD-switch}.
The results from time laboratories studies are summarized in Table~\ref{tab:timelabs}.
USA (NIST) and Italy (INRIM) have WR installations, see Table~\ref{tab:timelabs}.
% This prompted the development of the Low-Jitter Daughterboard
% \cite{biblio:WR-LJD} that improves the performance of the WR switch to 1e-12 without any
% modifications to the WR-PTP Protocol, see
% \cite{biblio:MIKES-50km}\cite{biblio:SYRTE-LNE-500km}\cite{biblio:WR-ultimate-limits}
% The improved WR Switches are now commercially available \cite{biblio:WR-LJD-switch}.
% The results from time laboratories studies are summarized in Table~\ref{tab:timelabs}.
\begin{table}[!ht]
\caption{}
\centering
......@@ -337,9 +327,9 @@ NPL & &
INRIM & 70k m & bidir. in WDM & 610ps $\pm$47ps& & \cite{biblio:WR-INRIM} \\ \cline{2-6}
& 400km & unidir. in DWDM & & & \cite{biblio:WR-INRIM-400km} \\ \hline
\multicolumn{6}{|l|}{WDM = Wavelength Division Multiplexing} \\
\multicolumn{6}{|l|}{DWDM = Dense Wavelength Division Multiplexing} \\
\multicolumn{6}{|l|}{CWDM = Coarse Wavelength Division Multiplexing} \\
\multicolumn{6}{|l|}{(D/C)WDM = (Dense/Coarse) Wavelength Division Multiplexing} \\
% \multicolumn{6}{|l|}{DWDM = Dense Wavelength Division Multiplexing} \\
% \multicolumn{6}{|l|}{CWDM = Coarse Wavelength Division Multiplexing} \\
\multicolumn{6}{|l|}{\#~ Dedicated and commercial quasi-bidirectional optical amplifiers are used \cite{biblio:optical-amplifier}} \\
\multicolumn{6}{|l|}{*~ Low Jitter Daughterboard was used to enhance performance \cite{biblio:WR-LJD} } \\
\multicolumn{6}{|l|}{** Input stage of the Grandmaster was improved, the bandwidth of } \\
......@@ -348,7 +338,24 @@ INRIM & 70k m & bidir. in WDM
\end{tabular}
\label{tab:timelabs}
\end{table}
MIKES and INRIM
use WR to provide their realization of UTC to clients, e.g. UTC(MIKE) over a 50~km
link to the Metsähovi Observatory \cite{biblio:MIKES-50km} for applications in geodesy,
% (International GNSS Service,
% Very-long-baseline interferometry and satellite laser ranging)
UTC(INRIM) over
400~km to the financial district of Millano. NIST and LNE-SYRTE use WR to distribute
within their campus UTC(NIST) and UTC(OP), respectively. All
laboratories are studying WR with different types and lengths of fiber links and attempt to
increase its performance, see Table~\ref{tab:timelabs}.
These studies have shown that the stability (at tau=1s) of the off-the-shelf
WR switch is 1e-11 (Alan Deviation, ADEV, similar to a typical frequency counter e.g. Keysight 53230A)
and can be improved to 1e-12 without any modifications to the WR-PTP Protocol, see
Section~\ref{sec:JitterAndStability} and
\cite{biblio:MIKES-50km}\cite{biblio:SYRTE-LNE-500km}\cite{biblio:WR-ultimate-limits}.
Many of the National Time Laboratories are now working together with other WR users
and companies within the EU-founded projects to make prepare WR for industrial applications
\cite{biblio:WRITE}.
% At CERN, the General Machine Timing controller of the Antiproton Decelerator (AD)
% is synchronized with WR link to a similar controller of the LHC Injection
% Chain (LHC) that provides the beam also for AD. Such a WR link provides traceability
......@@ -393,14 +400,14 @@ INRIM & 70k m & bidir. in WDM
\section{Time-Triggered Control (TC)}
\label{sec:time-triggered-ctrl}
\subsection{Basic Concept}
% \subsection{Basic Concept}
Many accelerators, synchrotrons and spallation sources are controlled by triggering
events in a pre-configured sequence of actions. In fact, it is a very convenient
way to control beams of particles that move at very high speeds -- often close
to the speed of light -- faster than the propagation of control signals.
In the \textit{time-triggered control} schema, a sequence of actions is determined
In the time-triggered control schema, a sequence of actions is determined
by a controller and distributed to controlled devices in advance. These actions
are scheduled to be executed by spatially-distributed devices at a particular time.
The responsiveness of such systems greatly depends on the latency of
......@@ -410,7 +417,7 @@ these devices and the controller. WR provides precise and accurate synchronizati
upper-bound in latency through the network to enable the implementation of a time-triggered control
for accelerators.
\subsection{Example Applications}
% \subsection{Example Applications}
WR is used at GSI (Darmstadt, Germany) as the basis for a
......@@ -420,10 +427,10 @@ WR-based GMT has replaced the previously used system for the existing GSI
accelerators and will control GSI's new Facility for Antiproton and Ion Research
(FAIR) \cite{biblio:GSI-WR-GMT}. Control of GSI and FAIR requires that the
control-information is delivered from a common controller to any of the controlled
subsystems in any of the accelerators within 500$\mu s$. The most demanding of
subsystems in any of the accelerators within 500$\mu$s. The most demanding of
these subsystems require an accuracy of 1-5ns. The controller, called Data Master,
is a WR node. The subsystems are either WR Nodes or have a direct interface with WR Nodes.
All these WR nodes are connected to a common WR Network that provides synchronization,
is a WR node. The subsystems are either WR nodes or have a direct interface with WR Nodes.
All these WR nodes are connected to a common WR network that provides synchronization,
delivers control-information from the Data Master to all subsystems as well as
between subsystems, and allows diagnostics.
......@@ -438,10 +445,10 @@ June 2018.
Although a WR-based GMT to control CERN accelerators has been the reason for WR's
conception and it is yet to be implemented at CERN.
Both, at CERN and GSI, the same WR network that is used for time-triggered control
can provide to subsystems precise time and frequency which can be used,
for example, to timestamp input signals, an application described in the following
section.
% Both, at CERN and GSI, the same WR network that is used for time-triggered control
% can provide to subsystems precise time and frequency which can be used,
% for example, to timestamp input signals, an application described in the following
% section.
%
% GSI Helmholtz Centre for Heavy Ion Research \\
......@@ -451,19 +458,25 @@ section.
% \newpage
\section{Precise Timestamping (TS)}
\label{sec:timestamping}
\subsection{Basic Concept}
% \subsection{Basic Concept}
In a great number of applications, time and frequency are transferred in order
to timestamp accurately and/or precisely incoming signals. Such incoming signals
can be either discrete pulses that are timestamped with time-to-digital converters
or analogue signals that are sampled (digitized) with the distributed frequency
and associated with the distributed time. Timestamps are usually produced to
measure the time of flight (ToF) or correlate events between distributed systems. In
such cases, accurate and precise synchronization between these systems is required.
If timestamps are used to measure the duration of events detected by distributed subsystems,
precision and frequency stability are required, accuracy is not so important.
measure the time of flight (ToF) or correlate events between distributed systems.
% In
% such cases, accurate and precise synchronization between these systems is required.
% If timestamps are used to measure the duration of events detected by distributed subsystems,
% precision and frequency stability are required. %, accuracy is not so important.
Precise timestamping is one of the most widely-used applications of WR.
The ability
to timestamp input signals and send them over WR network to a standard PC for
analysis proves to be an extermely convenient solution to many otherwise
challenging measurements.
\subsection{Example Applications}
% \subsection{Example Applications}
% \textcolor{gray}{
% The first application of WR was in the second run of the CERN Neutrinos to Gran
......@@ -480,29 +493,41 @@ The most demanding WR applications in terms of timestamping are cosmic ray and
neutrino detectors that record the time of arrival of particles in individual
detector units distributed over up to kilometers. Based on the difference
in the time of arrival, the trajectory of particles are calculated. For these
applications, a high precision and accuracy is required in very harsh
environmental conditions due to their locations
\textcolor{red}{ (in the framework of the \cite{TAIGA-WR-harsh-env})}.
applications, a high precision and accuracy is required in harsh
environmental conditions due to their locations \cite{biblio:TAIGA-WR-harsh-env}.
The Large High Altitude Air Shower Observatory (LHAASO), located at 4410m above
sea level in China (Tibert), requires a 500~ps RMS \cite{biblio:LHAASO} alignment
of timestamps produced by 7000 WR nodes distributed over $1~km^2$ and exposed to
day-night variation of -10 to +55 degrees Celsius . To meet such requirements, active
of timestamps produced by 7000 WR nodes distributed over 1~km$^2$ and exposed to
day-night variation of -10 to +55 degrees Celsius. To meet such requirements, active
compensation of temperature-related hardware delays has been implemented
\cite{biblio:LHAASO-WR-temp} and each of the WR nodes will be individually
calibrated using a portable calibrator \cite{biblio:LHAASO-WR-calibrator}.
These methods have proved to work in a prototype installation that has been running
since 2014 (50 WR nodes, 4 WR switches in 4 layers, \cite{biblio:LHAASO-WR-prototype}).
The Cubic Kilometre Neutrino Telescope (KM3NeT)\cite{biblio:KM3NeT} is a research
infrastructure housing the next generation neutrino telescopes located at the
bottom of the Mediterranean Sea, off-shore France and Italy. The needed angular
resolution of 0.1 degree means that the submerged \textit{digital optical modules} (DOMs),
which constitute KM3NeT, must be synchronized with 1~ns accuracy and a
few 100~ps precision. 4140 DOMs at 3500~m depth 100~km off-shore of Italy and
2070 DOMs at 2475~m depth 40~km off-shore France will be synchronized with an on-shore
reference using WR network \cite{biblio:WR-KM3NeT-Letter}\cite{biblio:WR-KM3NeT-presentation}.
Initial tests have been succesfully performed with 18 DOMs off-shore France and Italy to validate the system.
Other applications of WR that use timestamping include the
Cubic Kilometre Neutrino Telescope (KM3NeT)
\cite{biblio:KM3NeT}\cite{biblio:WR-KM3NeT-Letter}\cite{biblio:WR-KM3NeT-presentation}
located at the bottom of the Mediterranean Sea, the
Tunka Advanced Instrument for Gammy ray and cosmic ray Astrophysics (TAIGA) project in Siberia
\cite{biblio:TAIGA-WR-1}\cite{biblio:TAIGA-WR-2}\cite{biblio:TAIGA-WR-harsh-env},
Cherenkov Telescope Array to be built in Chile and Spain \cite{biblio:CTA-WR-timestamps},
the Extreme Light Infrastructures in Hungary \cite{biblio:ELI-ALP-WR} and Czech Republic
\cite{biblio:ELI-BEAMS-WR}, Satellite Laser Ranging at German Aerospace Center
or Power Industry and Smart Grid studied at Swiss Federal
Institute of Technology Lausanne (EPFL) \cite{biblio:EPFL-WR-PMU}.
% The Cubic Kilometre Neutrino Telescope (KM3NeT)\cite{biblio:KM3NeT} is a research
% infrastructure housing the next generation neutrino telescopes located at the
% bottom of the Mediterranean Sea, off-shore France and Italy. The needed angular
% resolution of 0.1 degree means that the submerged \textit{digital optical modules} (DOMs),
% which constitute KM3NeT, must be synchronized with 1~ns accuracy and a
% few 100~ps precision. 4140 DOMs at 3500~m depth 100~km off-shore of Italy and
% 2070 DOMs at 2475~m depth 40~km off-shore France will be synchronized with an on-shore
% reference using WR network \cite{biblio:WR-KM3NeT-Letter}\cite{biblio:WR-KM3NeT-presentation}.
% Initial tests have been succesfully performed with 18 DOMs off-shore France and Italy to validate the system.
% \textcolor{gray}{
% Other applications of WR that use timestamping include the Cherenkov Telescope Array
......@@ -517,7 +542,7 @@ Initial tests have been succesfully performed with 18 DOMs off-shore France and
\section{Trigger Distribution (TD)}
\label{sec:triggers-distribution}
\subsection{Basic Concept}
% \subsection{Basic Concept}
Trigger distribution combines, to some extend, the time-triggered control and precise timestamping
described before. In this application, an input trigger signal is timestamped by a WR node and sent over the
WR network to many WR nodes that act upon the received message simultaneously, at
......@@ -531,7 +556,7 @@ In order to make sure that all the "interested" nodes act upon the trigger
simultaneously, the delay between the input trigger and the time of execution
is set to be greater than the upper-bound latency.
\subsection{Example Applications}
% \subsection{Example Applications}
The trigger distribution schema has been used at CERN since 2015 in the
WR Trigger Distribution (WRTD) system for instability
......@@ -539,13 +564,13 @@ diagnostics of the LHC \cite{biblio:WR-LIST}\cite{biblio:WR-LIST-2}.
In the WRTD, there is a number of instruments capable of detecting
LHC instabilities and continuously acquiring data in circular buffers. Upon detection of instabilities, such a device generates a
pulse that is timestamped by a Time-to-Digital Converter (TDC) integrated in
a WR Node, as depicted in Figure~\ref{fig:WRTD}.
a WR Node \cite{biblio:fmc-tdc-5cha}, as depicted in Figure~\ref{fig:WRTD}.
The timestamp produced by the TDC is broadcast over the WR network,
with a user-assigned identifier, allowing to uniquely identify the source of the
trigger. WR nodes interested in this trigger take its timestamp, add
a fixed latency (300$\mu s$) and produce a pulse at the calculated moment. This
pulse is an input to a device that continuously acquires beam monitoring
data in a round buffer. These buffers are deep enough to accommodate the introduced
data in a circular buffer. These buffers are deep enough to accommodate the introduced
fixed latency so that they can be rolled back to provide diagnostic data of the
beam at the time the instability was detected by the source device. In such way,
the onset of instabilities can be coherently recreated. It is worth noting
......@@ -571,7 +596,9 @@ OASIS to diagnose LHC and to improve its performance, the distribution of trigge
is being upgraded to use WR. The WR-based trigger distribution in OASIS is meant
to be generic and reusable. It is developed within the White Rabbit eXtensions
for Instrumentation (WRXI) project \cite{biblio:WRXI} that is based on the existing LAN
eXtensions for Instrumentation (LXI) standard, extending it when necessary. The WRXI
eXtensions for Instrumentation (LXI) standard.
% , extending it when necessary
The WRXI
for OASIS is meant to be operational in 2019.
% \textcolor{gray}{
......@@ -582,7 +609,7 @@ for OASIS is meant to be operational in 2019.
\section{Fixed-Latency Data Transfer (FL)}
\label{sec:fixed-latency}
\subsection{Basic Concept}
% \subsection{Basic Concept}
Fixed-latency data transfer provides a well-known and precise latency of data
transmitted between WR nodes in the WR network. It uses very similar
principles to the trigger distribution described in Section~\ref{sec:triggers-distribution}.
......@@ -598,14 +625,13 @@ WR nodes in the WR network will execute the same action at the same time. In
order to take advantage of the precise fixed-latency data transfer, the
application needs to be integrated with a WR node.
\subsection{Example Applications}
% \subsection{Example Applications}
The fixed-latency data transfer is used in the BTrain-over-WhiteRabbit (WR-BTrain)
\cite{biblio:WR-Btrain} system that distributes in real-time the value of the magnetic field in
real-time in CERN accelerators.
\cite{biblio:WR-Btrain} system that distributes in real-time the value of the magnetic field in CERN accelerators.
In circular accelerators, the acceleration of the beam by radio-frequency (RF) cavities
needs to be synchronized with the increase of magnetic field (B-field) in the
needs to be synchronized with the increase of magnetic field in the
bending magnets. BTrain is the system at CERN that measures and distributes the
value of the magnetic field (B-value) in real-time to the RF cavities,
power converters and beam instrumentation.
......@@ -634,8 +660,8 @@ with latency of $10\mu s\pm 8ns$.
The WR-BTtrain has been successfully evaluated in the PS accelerators where it has
been running operationally since 2017 \cite{biblio:WR-BTrain-RF}. By 2021, all
the accelerators should be running WR-BTrain operationally \cite{biblio:WR-Btrain-status}.
For each accelerator, a separated WR-BTrian system is installed consisting of 1-2
WR switches and 2-5 WR nodes.
% For each accelerator, a separated WR-BTrian system is installed consisting of 1-2
% WR switches and 2-5 WR nodes.
% \textcolor{gray}{
% Fixed-latency data transfer is considered for the operation of the
......@@ -647,7 +673,7 @@ WR switches and 2-5 WR nodes.
\section{Radio-Frequency Transfer (RF)}
\label{sec:RFoverWR}
\subsection{Basic Concept}
% \subsection{Basic Concept}
Radio-frequency transfer allows to digitize periodic input signals in a WR master node, send
their digital form over a WR network, and then regenerate this signal coherently with a fixed delay in many
WR slave nodes. In such schema, depicted in Figure~\ref{fig:RFoverWR} and detailed in \cite{biblio:WR-LIST},
......@@ -664,12 +690,13 @@ input RF signal. The error measured by the phase detector is an input to a
loop filter (e.g. Integral-Proportional controller) that steers the DDS to produce a signal identical
to the RF input - effectively the DDS is locked to the input signal.
The tuning words of the DDS are the digital form of the RF input
that is sent over WR network. Each of the receiving WR nodes recreate the RF input signal
that is sent over WR network. Each of the receiving WR nodes recreates the RF input signal
by using the received tuning words to control the local DDS with a fixed delay.
In such way, the WR slave nodes produce RF outputs that are syntonized with
the RF input, phase-aligned among each other with sub-ns accuracy and picoseconds precision, and precisely delayed with respect to the RF input.
the RF input, phase-aligned among each other, and delayed with respect to the RF input --
all with sub-ns accuracy and picoseconds precision.
\subsection{Example Applications}
% \subsection{Example Applications}
The WR-based radio-frequency transfer is being implemented in the European Synchrotron Radiation
......@@ -684,11 +711,10 @@ process. Apart from the 352~MHz signal, other frequencies are distributed, such
The current ESRF "Bunch Clock" system is being refurbished to use WR \cite{biblio:ESRF-WR}.
The solution has passed a 6-months validation tests in 2015. In 2016, a prototype system
consisting of a WR switch, a WR master node and a WR slave node successfully injected
successfully injected
bunches in the storage ring providing $<$10ps jitter. A system consisting
of one master and seven slaves is expected to be operational in July 2018. It
will be expanded to 40 WR slaves nodes and 4-5 WR switches by 2020.
of a WR switch and eight WR nodes is expected to be operational in July 2018. It
will be expanded to 41 WR nodes and 4-5 WR switches by 2020.
The ESRF "Bunch Clock" system not only distributes a number of RF frequencies,
it also provides timestamps and triggers that can be synchronous with these RF
frequencies.
......@@ -1094,48 +1120,57 @@ These requirements necessitate enhancements of WR performance.
\section{Performance Enhancements}
\label{sec:WRenhancements}
The growing number of applications catalyzes constant improvements
of WR performance. These are summarized in this section.
The growing number of applications catalyzes improvements
of WR performance that are summarized in this section.
\subsection{Jitter and Clock Stability}
\label{sec:}
\label{sec:JitterAndStability}
The applications of WR for time and frequency transfer in National Time Laboratories
as well as for RF transfer in CERN's SPS require improvement of jitter and clock
stability.
The frequency transfer over WR network was characterized in
\cite{biblio:WR-characteristics} and its ultimate performance limits
studied in \cite{biblio:WR-ultimate-limits}. The studies show that the
performance of a WR switch currently commercially available can be
improved as follows:
studied in \cite{biblio:WR-ultimate-limits}. The studies
\cite{biblio:WR-ultimate-limits}\cite{biblio:MIKES-50km}\cite{biblio:SYRTE-LNE-500km}
have shown that the performance of a WR switch currently commercially available can be
improved:
\begin{itemize}
\item ADEV clock stability (tau=1s) from 1e-11 to 1e-12,
\item Random jitter from 11 to 1.1~ps RMS
over 1Hz-100kHz.
\end{itemize}
This prompted the development of the Low-Jitter Daughterboard
\cite{biblio:WR-LJD} that improves the performance of the WR switch to 1e-12 without any
modifications to the WR-PTP Protocol, see
\cite{biblio:MIKES-50km}\cite{biblio:SYRTE-LNE-500km}\cite{biblio:WR-ultimate-limits}.
The improved WR Switches are now commercially available \cite{biblio:WR-LJD-switch}.
A high performance low-jitter WR node is developed for the SPS's RF transmission
achieving jitter of sub-100fs RMS from 100Hz to 20MHz \cite{biblio:SPS-WR-LLRF}.
\subsection{Temperature Compensation}
\label{sec:}
The studies \cite{biblio:LHAASO-WR-temp} have shown that the temperature variation
The studies \cite{biblio:wr-cngs} have shown that the temperature variation
of WR nodes and switches degrades synchronization performance, still
maintaining sub-ns accuracy over the measured 45 degrees Celsius temperature range.
maintaining sub-ns accuracy.
This degradation and its sources have been carefully characterized
\cite{biblio:wr-cngs} showing that its major contributor is the variation of hardware
delays (\textit{fixed delays}), considering links below 10~km (see next section).
\cite{biblio:LHAASO-WR-temp} showing that its major contributor is the variation of hardware
delays, considering links below 10~km (see next section).
These delays are usually calibrated for WR devices
\cite{biblio:wrCalibration} at a room temperature and assumed constant throughout
operation. Their variation however is linear with temperature and so an online
correction can be applied. Such real-time correction was developed for the LHAASO
experiment \cite{biblio:wr-cngs}. For temperatures between
-10 and 50 degrees Celsius, this method has shown to reduce the synchronization
peak-to-peak variation from 700~ps to $<$150ps with a standard deviation below 50 ps.
This online compensation
is used in LHAASO to ensure 500ps (rms)
synchronization of 7000 WR nodes exposed to harsh environmental conditions
correction can be applied. It was developed for the LHAASO
experiment \cite{biblio:wr-cngs} that requires 500ps RMS
synchronization of 7000 WR nodes in harsh environmental. For temperatures between
-10 and 50 degrees Celsius, such correction reduces the
peak-to-peak variation from 700~ps to $<$150ps with a standard deviation $<$50~ps \cite{biblio:LHAASO-WR-temp}.
% This online compensation
% is used in LHAASO to ensure 500ps (rms)
% synchronization of 7000 WR nodes exposed to harsh environmental conditions
\subsection{Long-haul Link}
\label{sec:LongLinks}
......@@ -1148,8 +1183,9 @@ This deteriorates accuracy due to an unknown asymmetry.
On the 137~km bidirectional link in the Netherlands \cite{biblio:MIKES+VSL},
dedicated optical amplifiers that work with bidirectional fibers are used in
an attempt to overcome these limitation. The tests so far have shown $<$8ns accuracy
and further improvements are being studied.
On the 950~km unidirectional link in Finland, GPS precise point positioning
while a new "in-site" calibration method developed at VLS is expected to calibrate
out this asymmetry (over a 2x 137km link) to a few 0.1~ns or less \cite{biblio:VLS-WR-insite-calib}.
On the 950~km unidirectional link in Finland \cite{biblio:MIKES+VSL} , GPS precise point positioning
(PPP) was used to calibrate asymmetry and achieve $\pm$2~ns accuracy. This
method requires re-calibration after any disruption of the network. Laboratory
tests of a 500km WR connection using five cascaded WR devicies and four 125km unidirectional
......@@ -1164,11 +1200,11 @@ parameter, is calibrated at room temperature and assumed constant.
However, the variation of fiber temperature results in changes of the actual
\textit{alpha} (-0.12~ps/km/K for 1310/1490~nm and -0.05~ps/km/K for 1490/1550~nm)
while the variation of WR nodes/switches temperature result in laser wavelength
variation, e.g. 17~ps/nm km for 1550 nm \cite{biblio:SKA-80km}. These and other
variation, e.g. 17~ps/nm km for 1550 nm. These and other
effects analyzed in \cite{biblio:SKA-80km} are significant on long links and
can amount to over 5ns inaccuracy for bidirectional link using 1490/1550nm
and exposed to 50 Celsius degrees temperature variation. The Square Kilometre Array (SKA) \cite{biblio:SKA}
radio telescope mitigates these effects to achieve $<$1ns accuracy on 80~km links
can amount to over 5~ns inaccuracy for bidirectional link using 1490/1550nm
and exposed to 50 degrees Celsius temperature variation. The Square Kilometre Array (SKA) \cite{biblio:SKA}
radio telescope mitigates these effects to achieve $<$1~ns accuracy on 80~km links
by using DWDM SFP on ITU channels C21/C22 (1560.61/1558.98~nm) and combining them
on a single fiber via a simple DWDM channel filter, as described in \cite{biblio:SKA-80km}.
......@@ -1190,9 +1226,10 @@ on a single fiber via a simple DWDM channel filter, as described in \cite{biblio
The accuracy of WR depends greatly on the calibration of hardware delays. WR uses
procedures for relative calibration of these delays \cite{biblio:wrCalibration}.
With relative calibration, sub-ns accuracy can be achieved provided that the
synchronized WR devices are calibrated against the same "golden calibrator". This is
because the obtained values of hardware delays are estimates that are biased. The bias
cancels out only when WR devices calibrated to the same calibrator are connected.
synchronized WR devices are calibrated against the same "golden calibrator".
% This is
% because the obtained values of hardware delays are estimates that are biased. The bias
% cancels out only when WR devices calibrated to the same calibrator are connected.
% Relative calibration is performed for a complete WR device (e.g. a given version of WR switch and SFPs)
% and needs to be repeated each time a composing elements changes.
An ongoing work on absolute calibration \cite{biblio:WR-calibration} allows
......@@ -1205,33 +1242,48 @@ devices with this component.
\label{sec:WRin1588}
The P1588 Working Group \cite{biblio:P1588} is revising the
IEEE1588 standard, due to finish by the end of 2019. This group has been studying the
protocol extensions implemented in WR in order to incorporate a generalized
IEEE1588 standard, due to finish in 2019. This group has been studying
WR in order to incorporate its generalized
version into the standard \cite{P1588-HA-enhancements}.
As a result, one of the additions to the standard
is a third Default PTP Profile: High Accuracy.
This profile mandates a number of IEEE1588's new optional features that
are functionally equivalent to WR-PTP and that allow the support of WR hardware.
This resulted in a third Default PTP Profile, High Accuracy,
% As a result, one of the additions to the standard
% is a third Default PTP Profile: High Accuracy.
that mandates a number of IEEE1588's new optional features. All together, these
additions are functionally equivalent to WR and allow the support of WR hardware.
Along with the new features, informative annexes are added with a "standardized"
description of the WR calibration procedures \cite{biblio:wrCalibration} and
an example implementation of the High Accuracy profile implementation that achieves
an example implementation of the High Accuracy profile that achieves
sub-ns synchronization, a.k.a White Rabbit. The mapping between WR and High Accuracy
is described in \cite{biblio:WRin1588}.
\section{Conclusions}
\label{sec:conclusions}
conclusion
\\
\\
\\
\\
\\
\\
\\
\\
\\
\\
The number of WR applications and their specifications (link lenght, synchronization
performance) have exceeded the original requirements of the project.
This profileration of applications can be attributed to the fact that WR is based
on standards, it is openly as well as commercially available, and it has a very
active community. Open nature of the project allows WR users to contribute with their
specific expertise and new developments opening the WR to even more applications.
WR has become a \textit{de facto} for synchronization in scientific installations.
and it is now becoming industry standard within the IEEE1588.
With its wide adaptation in science, commercial support, up-coming
standardization and EU-founded project to catalyze applications in the
industry, we can conclude that WR applications will continue to proliferate in
science and should soon find its way into industry.
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