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Fragmentation-free ultrastable transfers through shared optical fibers
Vojtěch, J. ; Smotlacha, V. ; Havliš, O. ; Šlapák, M. ; Altmannová, L. ; Kundrát, J. ; Vohnout, R. ; Velc, R. ; Čížek, Martin ; Hrabina, Jan ; Řeřucha, Šimon ; Pravdová, Lenka ; Lazar, Josef ; Číp, Ondřej ; Kuna, Alexander ; Roztočil, J.
Fibre optics transfers of precise time and ultra-stable optical frequency are gradually becoming part of portfolio of network services of research and educational networks. These national infrastructures very often share fibres with regular data transmission, because of significant share of fibre cost rental on the Total Cost of Ownership (TCO). Situation is very similar in the Czech Republic, where there was more than 3000 km of ultra-stable transmissions within Czech e-Infrastructure, which itself runs over about 5800 km of dark fibre lines.
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Time and frequency transfer in all-optical network
Smotlacha, V. ; Kuna, Alexander
This paper describes usage of all-optical network for time metrology application - Time and frequency transfer between two geographically distant sites. Although several approaches exist, there is no production implementation yet. Our method is based on newly developed adapters utilizing channels in a DWDM (Dense Wavelength-Division Multiplexing) network. We present results of tests performed in real production all-optical network including the time transfer between atomic clocks in Prague and Vienna over more than 500 km long optical path
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Time and Frequency Transfer Using Satellite Based Augmentation System GAGAN
Pánek, Petr ; Kuna, Alexander
Aided Geo Augmented Navigation) is an Indian SBAS (Satellite Based Augmentation Systems). In contrast to the European EGNOS, this system already supports the navigation function and it transmits signals both in L1 and L5 frequency channels. We used the GAGAN signals for an experimental common-view time transfer between IPE Prague and PTB Braunschweig which is a distance of 370 km and we also tested the time transfer properties using a single clock common-view. The L1 and ionosphere-free code measurements have markedly lower accuracy compared to a GPS common-view because of rather narrow bandwidth of the SBAS signal in L1 frequency channel. L5 code measurement provides much better precision. It results from the single clock common-view that the observed fluctuations can be described as white noise with standard deviations of 6 ns, 1.3 ns and 14 ns for L1, L5 and ionosphere-free combination. The results obtained from the carrier phase measurements are promising. The single clock common-view precision was approximately 30 ps RMS even for the ionosphere-free combination.
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Optical infrastructure for time and frequency transfer
Smotlacha, V. ; Vojtěch, J. ; Kuna, Alexander
The paper describes optical infrastructure for time and frequency transfer in the Czech republic. The infrastructure is heterogeneous and utilises resources of the Czech academic optical network. It allows to interconnect Cesium standards in distant sites with the national time and frequency laboratory and to distribute accurate time and stable frequency. We also present results and compare them with other methods of time transfer
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