A VLBI experiment using a remote atomic clock via a coherent fibre link

Clivati, Cecilia; Ambrosini, R.; Artz, Thomas; Bertarini, Alessandra; Bortolotti, C.; Frittelli, M.; Levi, Filippo; Mura, Alberto; Maccaferri, G.; Nanni, M.; Negusini, M.; Perini, Federico; Roma, Mauro; Stagni, Matteo; Zucco, Massimo; Calonico, Davide

doi:10.1038/srep40992

Cited by 105 publications

(58 citation statements)

References 18 publications

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“…These efforts combined would give final evidence that VLBI observations synchronized by optical clocks can outperform those carried out using HMs in terms of stability and accuracy. We believe that the work presented here, together with other similar experiments described by Clivati et al (2015), Perini et al (2016), and Clivati et al (2017), will start a discussion within the VLBI community on the potential benefits of a traceable, remote synchronization of VLBI stations either using HMs or even more stable and accurate optical clocks.…”

Section: Discussionmentioning

confidence: 97%

“…It may be converted to electrical RF domain by an optical frequency comb (Newbury & Swann 2007), this, however, seriously increases the cost and complexity of the overall installation. Nevertheless, first experiments using this technique for characterization of a HM at the Medicina VLBI station (Clivati et al 2015) and to synchronize a VLBI session (Perini et al 2016;Clivati et al 2017) have been performed.…”

Section: Fibre Optic Distribution Of Frequency and Timementioning

confidence: 99%

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Fibre-optic delivery of time and frequency to VLBI station

Krehlik

Buczek

Kołodziej

et al. 2017

A&A

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The quality of Very Long Baseline Interferometry (VLBI) radio observations predominantly relies on precise and ultra-stable time and frequency (T&F) standards, usually hydrogen masers (HM), maintained locally at each VLBI station. Here, we present an operational solution in which the VLBI observations are routinely carried out without use of a local HM, but using remote synchronization via a stabilized, long-distance fibre-optic link. The T&F reference signals, traceable to international atomic timescale (TAI), are delivered to the VLBI station from a dedicated timekeeping laboratory. Moreover, we describe a proof-of-concept experiment where the VLBI station is synchronized to a remote strontium optical lattice clock during the observation.

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Section: Discussionmentioning

confidence: 97%

Section: Fibre Optic Distribution Of Frequency and Timementioning

confidence: 99%

Fibre-optic delivery of time and frequency to VLBI station

Krehlik

Buczek

Kołodziej

et al. 2017

A&A

View full text Add to dashboard Cite

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“…Nevertheless, compared to mature, deployed fiber-based approaches [5][6][7][8][9][10][11][12][13][14][15], O-TWTFT is still at an early stage. Indeed, Refs.…”

Section: Introductionmentioning

confidence: 99%

“…To formally obtain the two-way time-transfer equations, we identify two events that occur at We can connect these definitions Eqns. (13) and (14) with the actual measurements, Eqns. (6) through (11)…”

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confidence: 99%

Femtosecond optical two-way time-frequency transfer in the presence of motion

et al. 2019

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Platform motion poses significant challenges to high-precision optical time and frequency transfer. We give a detailed description of these challenges and their solutions in comb-based optical twoway time and frequency transfer (O-TWTFT). Specifically, we discuss the breakdown in reciprocity due to relativity and due to asynchronous sampling, the impact of optical and electrical dispersion, and velocity-dependent transceiver calibration. We present a detailed derivation of the equations governing comb-based O-TWTFT in the presence of motion. We describe the implementation of real-time signal processing algorithms based on these equations and demonstrate active synchronization of two sites over turbulent air paths to below a femtosecond time deviation despite effective velocities of ±25 m/s, which is the maximum achievable with our physical setup. With the implementation of the time transfer equation derived here, we find no velocity-dependent bias between the synchronized clocks to within at two-sigma statistical uncertainty of 330 attoseconds.Work of the U.S. Government and not subject to copyright. PACS numbers. 06.30.Ft Time and frequency III.A.4 Velocity-Dependent Transceiver CalibrationIn the simplest case, the calibration constant, cal T  , in Eq. (1) reflects a time delay in the transceiver between the reference plane and the detection of the incoming pulses. However, each transceiver is far from a compact point and consists of a distributed set of optical components comprising optical oscillators, frequency combs, modulated cw lasers, optical transceivers for detecting the arrival time of frequency comb pulses, and optical transceivers for the communication-based O-TWTFT as is illustrated in Fig. 2 (and later in Fig. 4). Nevertheless, in the absence of significant Doppler shifts, as in Refs. [2][3][4], the calibration of this distributed system can still be lumped into a single overall time offset, cal T  . Here, with Doppler shifts, that is no longer the case and this calibration must be expanded to include a velocity-dependent contribution,

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“…Cascaded link technique was used in Europe for clock comparisons between National Metrology Institutes (NPL, PTB and LNE-SYRTE) [9][10][11]. It motivates a wide community of scientists, from fundamental to applied physics and industry, to consider this technique for various applications [12][13][14][15][16][17][18][19]. Projects aiming at creating metrological networks at national and continental scale over telecommunication fiber networks are pushing the technology forward, as their implementation requires a high level of maturity [20][21][22][23].…”

mentioning

confidence: 99%

First industrial-grade coherent fiber link for optical frequency standard dissemination

Guillou-Camargo¹,

Ménoret²,

Cantin³

et al. 2018

Appl. Opt.

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We report on a fully bidirectional 680 km fiber link connecting two cities for which the equipment, the setup, and the characterization are managed for the first time by an industrial consortium. The link uses an active telecommunication fiber network with parallel data traffic and is equipped with three repeater laser stations and four remote double bidirectional erbium-doped fiber amplifiers. We report a short-term stability at 1 s integration time of 5.4×10 in 0.5 Hz bandwidth and a long-term stability of 1.7×10 at 65,000 s of integration time. The accuracy of the frequency transfer is evaluated as 3×10. No shift is observed within the statistical uncertainty. We show a continuous operation over five days with an uptime of 99.93%. This performance is comparable with the state-of-the-art coherent links established by National Metrology Institutes in Europe. It is a first step in the construction of an optical fiber network for metrology in France, which will give access to an ultrahigh performance frequency standard to a wide community of scientific users.

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A VLBI experiment using a remote atomic clock via a coherent fibre link

Cited by 105 publications

References 18 publications

Fibre-optic delivery of time and frequency to VLBI station

Fibre-optic delivery of time and frequency to VLBI station

Femtosecond optical two-way time-frequency transfer in the presence of motion

First industrial-grade coherent fiber link for optical frequency standard dissemination

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