Virtual Atomic Clocks to the desk OPTIME project Authors (PSNC) Wojbor Bogacki (wojbor@man.poznan.pl, tel. +48 61 858 2028), Artur Binczewski (artur@man.poznan.pl),, Krzysztof Turza (kturza@man.poznan.pl), (AGH) Marcin Lipiński (mlipinsk@agh.edu.pl), Łukasz Śliwczyński (sliwczyn@agh.edu.pl), Przemysław Krehlik (krehlik@agh.edu.pl), (AOS) Jerzy Nawrocki (nawrocki@cbk.poznan.pl), Paweł Nogaś (pnogas@cbk.poznan.pl), Piotr Dunst (pdunst@cbk.poznan.pl) (GUM) Albin Czubla (a.czubla@gum.gov.pl) (OPL) Janusz Pieczerak (janusz.pieczerak@orange.com), Author Affiliations Poznań Supercomputing and Networking Center (PSNC), Orange Polska (OPL), Space Research Centre (AOS), University of Science and Technology Krakow (AGH), Central Office of Measures (GUM) Keywords Atomic clock, virtual atomic clock, fiber network, dark fibers, precise time and frequency transfer, atomic time scale, modern services Abstract Nowadays users are not satisfied with a simple network connection. Users need a variety of services embedded in the network environment like clouds, video on demand, secure access to company resources. One of these modern services which is just starting right know is time and frequency distribution. Time is one of the basic physical quantities, so its precise measure is needed in many areas of science and life, like radio astronomy, particle physics, laser optics, navigation, metrology, cellular networks or military systems. The progress of science is determined by accuracy of time and frequency measurements. Today the atomic clocks reach the highest accuracy and seem to be the perfect instrument, but unfortunately they have one major drawback high cost. In the other hand, satellite systems which are used now have physical restrictions to achieve better accuracy in transmitted signals. It causes that post processing of measurements results in satellite systems cannot achieve highest accuracy. Moreover, it is not possible to obtain high accuracy results in real time in satellite systems. These limitations caused that scientists from many countries are searching for new ways of time and frequency distribution. The answer to these issues is OPTIME project. The project implements, with success, solution of distributing time and frequency of high accuracy and stability clocks (e.g. Hmaser ) by a dedicated system based on a single dark fiber link. In contrast to other systems OPTIME is a self-calibrating one. It means that no external equipment for calibration is needed to make it fully operational.
The OPTIME project developed the system of distribution of time and frequency signals which includes reference time signal, distribution network and local time repository. Smooth and trouble-free operation of the distribution system depends on many elements. The first one is a continuous and stable access to atomic time & frequency signals. To achieve these features the system uses more than one atomic reference. The first one comes from the Space Research Centre - Astrogeodynamic Observatory (AOS) in Borowiec. The second one is available from the Central Office of Measures (GUM), which is responsible for realization of the official time in Poland. However, it should be noted that the architecture provided by OPTIME can include a larger number of atomic reference signals and choose the best ones as a reference. Moreover system uses specialized devices designed and constructed by AGH in Krakow to transmit time and frequency signals with the highest possible accuracy. The second element is the continuous transmission of time and frequency signals at a distance, in order to synchronize, and deliver them to local repositories. These local repositories distribute time and frequency signals to end-users such as research institutions, centers of advanced technologies, institutions related to navigation, military, or other units who need precise time and frequency. The local repository is also equipped with atomic clock which can handle time and frequency signals with a high level of accuracy in case of problems with connection with reference signals from remote atomic time scales. One of the local repositories is placed in Poznań Supercomputing and Networking Center, the second one is placed in National Laboratory of Atomic, Molecular and Optical Physics FAMO in Toruń. The next element, but not less important, is monitoring and management of time and frequency service. Due to foreign status of time and frequency signal in typical telecommunication networks (systems) it is impossible to use the same mechanism and management software for administration of this kind of service. That is why OPTIME engineers searched how to adapt and connect monitoring of time and frequency to telecommunication systems. Success of the OPTIME project can be measured by the fact that for more than 3 years it provides very reliable comparison of two UTC(k) laboratories (AOS and GUM). This connection (over 400 km long) is officially reported to Bureau International des Poids et Mesures (BIPM). This link was also used as a reference for the BIPM GNSS calibration system. The next important development is more than 300 km long link between PSNC and FAMO which delivers H-maser accuracy of time and frequency as a reference for the national project of building of the optical clock.
Figure 1. National Distribution System for Atomic Clocks Time and Frequency (T&F) Signals Acknowledgements OPTIME is a project co-founded by the National Centre for Research and Development in the Applied Research Programme. Vitae Artur Binczewski received the M.Sc. degree in Computer Science from the Poznan University of Technology in 1993. He is the Manager of Network Division at the PSNC. He was involved in several EC projects: SEQUIN (IST-1999-20841), ATRIUM (IST-1999-20675), 6NET (IST-2001-32063). He coordinated the Porta Optica Study (RI026617), PHOSPHORUS (IST034115), ADDONAS (PIANO+) projects and ALIEN(317880). He is author or co-author of papers in major professional journals and conference proceedings. Wojbor Bogacki, received the M.Sc. degree in Computer Science: Artificial Intelligence from the Wroclaw University of Technology in 2001. He works in Poznan Supercomputing and Networking Center in Network Division as a Senior Network Systems Analyst. He participated in several EC and Polish networking projects: GN3 (Project no. 238875), 6NET (IST-2001-32063), PHOSPHORUS (IST034115). His main interests concern networking and software developing technologies. Krzysztof Turza received his M.Sc. degree in Electronic and Telecommunication Science from Poznan University of Technology in 2004. From that year he works in the Network Department in Poznan Supercomputing and Networking Center. His research interests are in the areas of broadband optical networks and new generation networks. From the beginning of work in PSNC he is responsible for the
maintenance and administration of the DWDM system and switching devices in PIONIER network. Moreover he is responsible for optical phenomena measurements in the fiber network, especially chromatic and polarization dispersion. Janusz Pieczerak graduated as M.Sc. in Radioelectronics at Warsaw University of Technology in 1980. He is a researcher in Orange Labs Poland in the area of telecommunications, including next generation networks and business multimedia communication systems, as well as transmission and IP/MPLS telecommunication networks. He represents Orange Poland in standardization works in ITU-T Study Group 11 (Signalling requirements, protocols and test specifications) and Study Group 13 (Future networks including cloud computing, mobile and next-generation networks). He is responsible for development of telecommunication network synchronization systems and services based on delivery of precise time and frequency signals. Jerzy Nawrocki received the MSc. Physics (1976), Ph.D. Satellite Geodesy (1998). He is researcher at the Time and Frequency Department at the Astrogeodynamical Observatory of the Space Research Centre. He is a developer of the new, multi-system GPS/EGNOS/WAAS/GLONASS C/A and P-code time receiver TTS-3. He is a participant in the realization of the Prototype of the Galileo Time Service Provider, and in the development glass fibre link for high accuracy time&frequency link GUM(Warsaw) AOS Borowiec, 420 km length. He was involved in realization of BalticTime project: Reinforcing egovernment services in Baltic States through legal and accountable Digital Time Stamp. Pawel Nogaś received the MSc. Physics of Earth and Atmosphere (1998), and working on the Ph.D. thesis. He is a developer of the multi-system GPS/EGNOS/WAAS/GLONASS/GALILEO C/A and P- code time receiver TTS-4. He is a researcher, Time and Frequency Department at the Astrogeodynamical Observatory of the Space Research Centre, and participates in the development glass fibre link for high accuracy time&frequency link GUM(Warsaw) AOS Borowiec, 420 km length. He is also the Head of product development and manufacturing at Piktime Systems. Piotr Dunst - Graduated from Poznan University of Technology faculty of Technical Physics. Ph.D. student at Space Research Center. Works at Astrogeodynamical Observatory SRC in Time and Frequency Department. Attended an internship at National Physical Laboratory in London, where he was working with Primary Frequency Standard (PFS). Responsible for measurements conducted on optical fiber time link AOS-GUM. Specializes in designing experimental systems both hardware and software. Łukasz Śliwczyński was born in Rajcza, Poland in 1969. He received MSc and PhD degrees from AGH University of Science and Technology in Kraków, Poland, in 1993 and 2001, respectively. He was working on high-speed transmitters and receivers for digital fiber optic transmission systems, especially operating with unbalanced data streams. He also investigated 10 Gb/s transmitters with directly modulated lasers using optical filtering to mitigate distortions caused by chromatic dispersion of the fiber. His current interests include developing precise time and frequency transfer systems based on optical fibers. Przemysław Krehlik received his MSc and PhD degrees in electronics from AGH University of Science and Technology in Kraków, Poland, in 1988 and 1998, respectively. Since 1988 he has worked in Fiber Optic Transmission Group in Institute of Electronics, AGH. His R&D activity is focused on high-speed electronic circuits, direct modulation of semiconductor lasers, application specific fiber-optic systems, and optoelectronic measurement techniques.
Marcin Lipiński received his M.S in electronics in 1971 from Wrocław Technical University and joined the R&D Dept. of POLON Nuclear Equipment Plant where he worked as project manager on many CAMAC system products. In 1977 he moved to the Institute of Electronics at AGH University of Science and Technology where he received his Ph.D. in 1984. He has been engaged in several projects concerned with fiber-optic transmission applied in non-telecommunication fields such as military or contribution TV. He is currently managing the Fiber Optic Transmission Group and his present interest include precise fiber-optic reference time and frequency transfer. Albin Czubla received his M.S. and Ph.D. in physics from the Maria Curie-Skłodowska University, Lublin, Poland, in 1994 and 1999, respectively. He has been dealing with time and frequency metrology since 2002. His research interests are maintaining atomic timescales, stability analysis of time and frequency signals, precise time and frequency transfer over optical fibre and with GNSS techniques as well as analysis of uncertainty of measurement results. He is the head of Time and Frequency Laboratory, Electricity Department, Central Office of Measures (NMI in Poland) and a representative of Poland in Technical Committee of Time and Frequency of EURAMET.