Point-to-point stabilized optical frequency transfer with active optics

Dix-Matthews, Benjamin; Schediwy, Sascha; Gozzard, David; Savalle, Etienne; Esnault, François Xavier; Lévèque, Thomas; Gravestock, Charles; D'Mello, Darlene; Karpathakis, Skevos; Tobar, Michael E.; Wolf, Peter

doi:10.1038/s41467-020-20591-5

Cited by 54 publications

(35 citation statements)

References 72 publications

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“…This is due to broadband noise resulting from the EDFA repeatedly amplifying reflections resulting from the folded link. This is unlikely to be a problem in a real, bistatic, link, and this noise was not seen in point-to-point tests using the same EDFA and similar optical terminals (22). The amplitude stabilization system significantly increased the robustness of the link and enabled regular cycle-slip-free operation for periods of around 30 minutes in low turbulence, with the longest cycle-slip free period being 104 minutes at an average turbulence strength of Cn 2 = 6×10 −15 m −2/3 .…”

Section: Figmentioning

confidence: 99%

“…Ultra-stable frequency dissemination via optical fiber networks for optical atomic clock timescale comparison has been demonstrated over distances up to 1840 km (18)(19)(20) with fractional frequency instabilities as low as 6.9×10 −21 being achieved over 1400 km after an averaging time of 30,000 s (21). Various groups (22)(23)(24) are now applying similar stabilization techniques to free-space laser links, where the amplitude noise caused by atmospheric turbulence imposes additional challenges.…”

Section: Scopementioning

confidence: 99%

“…The amplitude stabilization system presented here is a modification of that demonstrated in (22). Figure S1 shows a simplified schematic of the amplitude stabilization inside the optical transceiver terminal.…”

Section: Tip-tilt Amplitude Stabilization Systemmentioning

confidence: 99%

“…The tunable laser was necessary because the output power of the phase stabilization system was not high enough for the QPD to detect after the losses of the link and terminal optics. Greater launch power from the phase stabilization system would negate the need for a separate beacon laser, as was done in (22). The tunable laser was tuned to a frequency of 192.7 THz (1555.75 nm) while the narrow linewidth laser of the phase stabilization system has a fixed frequency of 193.1 THz (1552.52 nm).…”

Section: Tip-tilt Amplitude Stabilization Systemmentioning

confidence: 99%

“…In order to estimate the theoretical noise floor of the phase stabilization system resulting from residual atmospheric noise and laser frequency noise when the phase stabilization system is active, we perform a similar analysis to that presented in (22). For a stationary noise process x(t) that has a PSD Sx(f), the linear combination of noise processes is given by…”

Section: Phase Stabilization System Noise Analysismentioning

confidence: 99%

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Ultrastable Free-Space Laser Links for a Global Network of Optical Atomic Clocks

et al. 2022

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A global network of optical atomic clocks will enable unprecedented measurement precision in fields including tests of fundamental physics, dark matter searches, geodesy, and navigation. Free-space laser links through the turbulent atmosphere are needed to fully exploit this global network, by enabling comparisons to airborne and spaceborne clocks. We demonstrate frequency transfer over a 2.4 km atmospheric link with turbulence similar to that of a ground-to-space link, achieving a fractional frequency stability of 6.1×10 −21 in 300 s of integration time. We also show that clock comparison between ground and low Earth orbit will be limited by the stability of the clocks themselves after only a few seconds of integration. This significantly advances the technologies needed to realize a global timescale network of optical atomic clocks.

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Section: Figmentioning

confidence: 99%

Section: Scopementioning

confidence: 99%

Section: Tip-tilt Amplitude Stabilization Systemmentioning

confidence: 99%

Section: Tip-tilt Amplitude Stabilization Systemmentioning

confidence: 99%

Section: Phase Stabilization System Noise Analysismentioning

confidence: 99%

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Ultrastable Free-Space Laser Links for a Global Network of Optical Atomic Clocks

et al. 2022

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Absolute Time Delay Measurement Over an Existing Radio Over Free‐Space Optical Link with Sub‐Picosecond Precision

Sun

Zhang

et al. 2023

Laser & Photonics Reviews

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Distributed RF systems are referred to as the fundamental structure for future wireless communication and sensors. To enable wideband coherent operation, synchronization across the distributed systems with massive parallel absolute time delay (ATD) measurements up to sub‐picosecond precision should be implemented. Traditional ways to achieve precise ATD measurements usually rely on probe signals with broad bandwidth, while that of RF systems is limited. Although an all‐optical solution has high precision, it is complex and not compatible with RF systems. Microwave photonics, which combines the merits of RF and photonics, potentially provides a low‐cost and high‐precision solution that can be deployed in existing RF systems. Here, ATD measurement with sub‐picosecond precision directly over an existing radio over free‐space optical (RoFSO) link, requiring no additional hardware beyond the link, is achieved. The bandwidth of the system is only 10 MHz, while the measurement results meet well with those obtained by optical combs. The measurement errors caused by atmospheric turbulence are well suppressed by a dynamic Kalman filter. The RoFSO links can be stabilized in a closed‐loop measurement. The standard deviation of the timing jitter is 0.28 ps, and the Allan variance is around 1.9 × 10−19 @ 1000 s, which is sufficient to synchronize millimeter‐wave signals.

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Estimation of Temporal Variations in the Earth’s Gravity Field Using Novel Optical Clocks Onboard of Low Earth Orbiters

Shabanloui,

Wu,

Müller

2023

International Association of Geodesy Symposia

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The current generation of optical atomic clocks has reached a fractional frequency uncertainty of 1$$\times $$ × 10$$^{-18}$$ − 18 (and beyond) which corresponds to a geopotential difference of 0.1 m$$^{2}$$ 2 /s$$^{2}$$ 2 . Those gravitational potential differences can be observed as gravitational redshift when comparing the frequencies of optical clocks. Even temporal potential variations might be determined with precise novel optical atomic clocks onboard of low-orbiting satellites such as SLR-like (e.g. LAGEOS-1/2) and GRACE-like missions.In this simulation study, the potential of precise space-borne optical clocks for the determination of temporal variations of low-degree Earth’s gravity field coefficients are investigated. Different configurations of satellite orbits, i.e. at different altitudes (between 400 and 6000 km) and inclinations, are selected as well as certain assumptions on the clock performance are made. A particular focus is put on how well degree-2 coefficients can be estimated from those optical clock measurements and how it compares to results from SLR.

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Point-to-point stabilized optical frequency transfer with active optics

Cited by 54 publications

References 72 publications

Ultrastable Free-Space Laser Links for a Global Network of Optical Atomic Clocks

Ultrastable Free-Space Laser Links for a Global Network of Optical Atomic Clocks

Absolute Time Delay Measurement Over an Existing Radio Over Free‐Space Optical Link with Sub‐Picosecond Precision

Estimation of Temporal Variations in the Earth’s Gravity Field Using Novel Optical Clocks Onboard of Low Earth Orbiters

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