Optical-Frequency Transfer over a Single-Span 1840 km Fiber Link

Droste, Stefan; Ozimek, F.; Udem, Thomas; Predehl, Katharina; Hänsch, Theodor W.; Schnatz, H.; Grosche, G.; Holzwarth, Ronald

doi:10.1103/physrevlett.111.110801

Cited by 257 publications

(105 citation statements)

References 31 publications

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“…(3), which depends on the square of the velocity, and therefore can safely be neglected in the foreseeable future. Corresponding contributions to the (classical) firstorder Doppler effect may be significant, as mentioned in Mai (2013), but fortunately first-order Doppler shifts do not play a role in optical clock comparisons through (two-way) fibre links, which presently is the only technique that has achieved link performances at the level of 1 part in 10 18 and below (Droste et al 2013). …”

Section: Time and The Gravity Potentialmentioning

confidence: 99%

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

Denker

Timmen

Voigt

et al. 2017

J Geod

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The frequency stability and uncertainty of the latest generation of optical atomic clocks is now approaching the one part in 10 18 level. Comparisons between earthbound clocks at rest must account for the relativistic redshift of the clock frequencies, which is proportional to the corresponding gravity (gravitational plus centrifugal) potential difference. For contributions to international timescales, the relativistic redshift correction must be computed with respect to a conventional zero potential value in order to be consistent with the definition of Terrestrial Time. To benefit fully from the uncertainty of the optical clocks, the gravity potential must be determined with an accuracy of about 0.1 m 2 s −2 , equivalent to about 0.01 m in height. This contribution focuses on the static part of the gravity field, assuming that temporal variations are accounted for separately by appropriate reductions. Two geodetic approaches are investigated for the derivation of gravity potential values: geometric levelling and the Global Navigation Satellite Systems (GNSS)/geoid approach. Geometric levelling gives potential differences with millimetre uncertainty over shorter distances (several kilometres), but is susceptible to systematic errors at the decimetre level over large distances. The GNSS/geoid approach gives absolute gravity potential values, but with an uncertainty corresponding to about 2 cm in height. For large distances, the GNSS/geoid approach should therefore be better than geometric levelling. This is demonstrated by the results from practical investigations related to three clock sites in Germany and one in France. The estimated uncertainty for the relativistic redshift correction at each site is about 2 × 10 −18 .

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Section: Time and The Gravity Potentialmentioning

confidence: 99%

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

Denker

Timmen

Voigt

et al. 2017

J Geod

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“…Optical fiber links are promising on continental scales as demonstrated up to 1840 km [12]. To bridge intercontinental distances, however, satellite based techniques are presently the only way.…”

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confidence: 99%

Direct comparison of optical lattice clocks with an intercontinental baseline of 9000 km

Hachisu¹,

Fujieda²,

Nagano³

et al. 2014

Opt. Lett.

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We have demonstrated a direct frequency comparison between two 87 Sr lattice clocks operated in intercontinentally separated laboratories in real time. Two-way satellite time and frequency transfer technique based on the carrier phase was employed for a direct comparison with a baseline of 9 000 km between Japan and Germany. A frequency comparison was achieved for 83 640 s resulting in a fractional difference of (1.1 ± 1.6) × 10 −15 , where the statistical part is the biggest contribution to the uncertainty. This measurement directly confirms the agreement of the two optical frequency standards on an intercontinental scale.

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“…We checked that we obtained the same long-term overlapping Allan deviation after averaging the data on 100 or 1000 successive points in order to eliminate any filtering effect associated with the lambda-type counting [50,51]. The frequency stability and accuracy are compatible with single-span optical links using dedicated fibres [31,32]. This is an unequivocal demonstration that public telecommunication networks can be used for ultra-stable and accurate frequency transfer.…”

Section: Ultra-stable Optical Frequency Transfer On Long-haul Fibre Lmentioning

confidence: 86%

“…2) and demonstrated a 172-km link using recirculation in the same fibres [23]. Following these pioneering results, several groups worldwide have initiated experiments on optical links [24,27,28,[30][31][32][46][47][48].…”

Section: Ultra-stable Optical Frequency Transfer On Long-haul Fibre Lmentioning

confidence: 99%

“…In the last decade, several experiments in Europe, USA and Japan have explored the limits of this method, paving the way for a new generation of ultra-stable optical networks [18,[21][22][23][24][25][26][27][28][29][30][31]. A groundbreaking frequency transfer has been demonstrated on a record distance of 920 km and even 1840 km on a dedicated fibre network [27,32]. The outcome of such a technique leads to high resolution comparisons between remote clocks in conjunction with the use of femtosecond frequency combs [26,[33][34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

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Frequency and time transfer for metrology and beyond using telecommunication network fibres

Lopez

Kéfélian

Jiang

et al. 2015

Comptes Rendus. Physique

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The distribution and the comparison of an ultra-stable optical frequency and accurate time using optical fibres have been greatly improved in the last ten years. The frequency stability and accuracy of optical links surpass well-established methods using the global navigation satellite system and geostationary satellites. In this paper, we present a review of the methods and the results obtained. We show that public telecommunication network carrying Internet data can be used to compare and distribute ultra-stable metrological signals over long distances. This novel technique paves the way for the deployment of a national and continental ultra-stable metrological optical network. RésuméLa distribution et la comparaison d'étalons de fréquence optique ultra-stables et d'échelle de temps ont été grandement améliorées depuis dix ans par l'emploi de fibres optiques. La stabilité de fréquence et l'exactitude des liens optiques fibrés surpassent les méthodes bien établies fondées sur les communications satellitaires. Dans cet article, nous présentons les méthodes et les résultats obtenus pendant cette décade. Nous montrons que les réseaux de télécommunication publics transportant des données internet peuvent être utilisés pour comparer et distribuer des signaux métrologiques sur de grandes distances. Ceci ouvre la voie au déploiement d'un réseau métrologique à l'échelle nationale et continentale.

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Optical-Frequency Transfer over a Single-Span 1840 km Fiber Link

Cited by 257 publications

References 31 publications

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

Geodetic methods to determine the relativistic redshift at the level of 10 $$^{-18}$$ - 18 in the context of international timescales: a review and practical results

Direct comparison of optical lattice clocks with an intercontinental baseline of 9000 km

Frequency and time transfer for metrology and beyond using telecommunication network fibres

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