Comparing a GPS time link calibration with an optical fibre self-calibration with 200 ps accuracy

Abstract

In Poland, an accurate two-way optical fibre time transfer (TWOTT) baseline of 420 km has been developed with a standard uncertainty of 112 ps. Meanwhile, the BIPM has been engaged in a pilot project to reduce the uncertainty of UTC GNSS time transfer calibrations from 5 ns to approximately 1.5 ns, for which it has developed a standard calibration scheme, named METODE, associated with an integrated portable GNSS calibration station. The TWOTT and the METODE respectively represent the world's most advanced time transfer method and calibration facility.In July 2013, the BIPM calibrator and the TWOTT self-calibrated optical fibre transceivers were set up side by side to compare their results. This is the first time that an operational TWOTT has been used in accurate time transfer and the first time that a GNSS calibration method has been validated with a technique accurate to 200 ps. As the two systems are completely independent and the latter is one order of magnitude more accurate than the first, this comparison allowed validation of the METODE and its uncertainty. It also confirmed that any bias in the TWOTT is at most 1 ns.

Absolute measurement of the 1S0 − 3P0 clock transition in neutral 88Sr over the 330 km-long stabilized fibre optic link

“…The frequencies of the clock transitions can be compared by the use of an optical frequency comb with the UTC(AOS) and UTC(PL) 12 13 via the OPTIME network 14 .…”

“…We report a system of two independent bosonic strontium optical lattice standards with 88 Sr probed with a single shared ultranarrow laser. The absolute frequency of the clock transition is measured by the use of a frequency-doubled Er:fibre polarization-mode-locked optical frequency comb referenced to the UTC(AOS) and UTC(PL) 12 13 via the 330 km-long stabilized fibre optic link of the OPTIME network 14 15 .…”

Combining GPS, BeiDou, and Galileo Satellite Systems for Time and Frequency Transfer Based on Carrier Phase Observations

“…It is difficult to assess the performance of the approach owing to the different variation characteristics of the two time and frequency references at the two ends of the time link [48,49]. Therefore, an experiment with a short time link is designed, where the two GNSS stations are equipped with a common time and frequency reference (UTC (NTSC)) to cancel-out this effect.…”

TWSTFT Link Calibration Report

“…Tour: a calibration tour is a round trip calibration campaign with start and closure measurements. It may include several laboratories 2 METODE was proposed in the frame of the BIPM pilot project (2011-2014) aiming at unifying the UTC time link calibration with an uncertainty ≤ 2 ns [2][3][4]. It is composed of a time link calibration scheme with the calibrator denoted Std B .…”

“…This report includes the calibration results of the Lab(k)-PTB TWSTFT link and closure measurement of the BIPM-Lab(k)-BIPM tour with the BIPM standard travelling calibration station (Std B As part of the BIPM Pilot Project, the METODE was developed to unify the UTC time link calibrations with a calibration uncertainty u B ≤ 2 ns [2][3][4][5], Since 2013, the Std B has visited the UTC labs OP, PTB, PL, AOS, TL, NMIJ, NICT, NIM (BSNC), and ROA [6]; experiments were made also at the BIPM, NIST and Lab(k) [7,8].…”