Time transfer through optical fibres over a distance of 73 km with an uncertainty below 100 ps

We demonstrate the capability of accurate time transfer using optical fibres over long distances utilizing a dark fibre and hardware which is usually employed in two-way satellite time and frequency transfer (TWSTFT). Our time transfer through optical fibre (TTTOF) system is a variant of the standard TWSTFT by employing an optical fibre in the transmission path instead of free-space transmission of signals between two ground stations through geostationary satellites. As we use a dark fibre there are practically no limitations to the bandwidth of the transmitted signals so that we can use the highest chip rate of the binary phase-shift modulation available from the commercial equipment. This leads to an enhanced precision compared with satellite time transfer where the occupied bandwidth is limited for cost reasons. The TTTOF system has been characterized and calibrated in a common-clock experiment at PTB, and the combined calibration uncertainty is estimated as 74 ps. In a second step the remote part of the system was operated at Leibniz Universitat Hannover, Institut fur Quantenoptik (IQ) separated by 73 km from PTB in Braunschweig. In parallel, a GPS time transfer link between Braunschweig and Hannover was established, and both links connected a passive hydrogen maser at IQ with the reference time scale UTC(PTB) maintained in PTB. The results obtained with both links agree within the 1-σ uncertainty of the GPS link results, which is estimated as 0.72 ns. The fibre link exhibits a nearly ten-fold improved stability compared with the GPS link, and assessment of its performance has been limited by the properties of the passive maser.

[1]  Przemyslaw Krehlik,et al.  Optical fibers in time and frequency transfer , 2010 .

[2]  Andreas Bauch,et al.  Advanced GPS-Based Time Link Calibration with PTB's New GPS Calibration Setup , 2010 .

[3]  G. Santarelli,et al.  86-km optical link with a resolution of 2 × 10-18 for RF frequency transfer , 2007, 0711.0933.

[4]  Christian Chardonnet,et al.  Simultaneous remote transfer of accurate timing and optical frequency over a public fiber network , 2013 .

[5]  Luigi Cacciapuoti,et al.  Space clocks and fundamental tests: The ACES experiment , 2009 .

[6]  Pierre Héroux,et al.  Precise Point Positioning Using IGS Orbit and Clock Products , 2001, GPS Solutions.

[7]  M. Fujieda,et al.  Time transfer through optical fibers (TTTOF): Progress on calibrated clock comparisons , 2010, EFTF-2010 24th European Frequency and Time Forum.

[8]  J. Kouba,et al.  GPS Precise Point Positioning Using IGS Orbit Products , 2001 .

[9]  Gesine Grosche,et al.  Phase-coherent comparison of two optical frequency standards over 146 km using a telecommunication fiber link , 2009, 0906.3476.

[10]  M. S. Millán.  Advanced optical correlation and digital methods for pattern matching—50th anniversary of Vander Lugt matched filter , 2012 .

[11]  T. Suzuyama,et al.  Time and frequency transfer and dissemination methods using optical fiber network , 2005, Proceedings of the 2005 IEEE International Frequency Control Symposium and Exposition, 2005..

[12]  D. Piester,et al.  Remote atomic clock synchronization via satellites and optical fibers , 2011 .

[13]  M. Fujieda,et al.  Time Transfer Through Optical Fibers (TTTOF): First Results of Calibrated Clock Comparisons , 2009, 1001.5406.

[14]  Mizuhiko Hosokawa,et al.  Stable radio frequency transfer in 114 km urban optical fiber link. , 2009, Optics letters.

[15]  A. Kuna,et al.  Time transfer using fiber links , 2010, EFTF-2010 24th European Frequency and Time Forum.

[16]  H. Schnatz,et al.  Remote frequency measurement of the 1S0 → 3P1 transition in laser-cooled 24Mg , 2011, 1107.3051.

[17]  T. Hänsch,et al.  A 920-Kilometer Optical Fiber Link for Frequency Metrology at the 19th Decimal Place , 2012, Science.

[18]  Sven-Christian Ebenhag,et al.  Measurements and Error Sources in Time Transfer Using Asynchronous Fiber Network , 2010, IEEE Transactions on Instrumentation and Measurement.

[19]  Otto Koudelka,et al.  Time transfer with nanosecond accuracy for the realization of International Atomic Time , 2008 .

[20]  Ying Li,et al.  Direct Comparison of Distant Optical Lattice Clocks at the 10-16 Uncertainty , 2011, 1108.2774.

[21]  N. Newbury,et al.  Coherent transfer of an optical carrier over 251 km. , 2007, Optics letters.