Calibration Comparison Between Optical Fiber and GPS Time Links

Z. Jiang, A. Czubla, J. Nawrocki, P. Nogas

Abstract:	One side, the recent developments in TWOTT (Two Way Optical Fiber Time Transfers) technique allows time transfer with a type A and B (uA and uB) combined uncertainty of a hundred ps. The 420 km baseline UTC(AOS)-UTC(PL) between two UTC laboratories AOS and PL is the first self-calibrated time link and operational permanently since 2012. On the other side, in the frame of improving the calibration uncertainty (the type B uncertainty uB) in the UTC time transfers, the BIPM launched in 2011 a pilot project, namely METODE (Measurement of Total Delay). It is composed of a calibration scheme and a travelling standard GNSS calibrator (StdB). The uB is evaluated to be 0.8~1.5 ns for accurate time link calibration. In July 2013, the BIPM StdB was setup at AOS and PL side by side with the TWOTT transceivers and we directly compared the two independent calibration results. Meanwhile using the METODE, we calibrated the GPS time transfer receivers of AOS and PL. Such on the baseline UTC(AOS)-UTC(PL) there are two sets of the time link results using GPS and TWOTT. This allows us indirectly comparing the GPS and TWOTT calibrations. This paper presents the experiment setups and the result of the comparison. Because GPS and TWOTT are two completely independent techniques and the latter is an order more accurate than the first, this experience allows us to validate the METODE time link calibration scheme using the StdB and evaluate its uncertainty.
Published in:	Proceedings of the 46th Annual Precise Time and Time Interval Systems and Applications Meeting December 1 - 4, 2014 Seaport Boston Hotel Boston, Massachusetts
Pages:	134 - 137
Cite this article:	Jiang, Z., Czubla, A., Nawrocki, J., Nogas, P., "Calibration Comparison Between Optical Fiber and GPS Time Links," Proceedings of the 46th Annual Precise Time and Time Interval Systems and Applications Meeting, Boston, Massachusetts, December 2014, pp. 134-137.
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