Ultra-Wideband Free-Space Optical Phase Stabilization

Dix-Matthews, Benjamin; Gozzard, David; Karpathakis, Skevos; Gravestock, Charles; Schediwy, Sascha

doi:10.1109/lcomm.2021.3053943

“…This can be accomplished with traditional AO 15 , 29 , or with novel “passive” methods such as photonic lanterns 30 or multi-plane light conversion 31 . In combination with atmospheric phase-stabilisation technology 32 – 34 , such a deployable optical terminal could even facilitate secure ground-to-LEO continuous variable quantum key distribution (CV-QKD) 35 .…”

Section: Resultsmentioning

confidence: 99%

Demonstration of 100 Gbps coherent free-space optical communications at LEO tracking rates

Walsh

¹

,

Karpathakis

²

,

McCann

³

et al. 2022

Sci Rep

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Free-space optical communications are poised to alleviate the data-flow bottleneck experienced by spacecraft as traditional radio frequencies reach their practical limit. While enabling orders-of-magnitude gains in data rates, optical signals impose much stricter pointing requirements and are strongly affected by atmospheric turbulence. Coherent detection methods, which capitalize fully on the available degrees of freedom to maximize data capacity, have the added complication of needing to couple the received signal into single-mode fiber. In this paper we present results from a coherent 1550 nm link across turbulent atmosphere between a deployable optical terminal and a drone-mounted retroreflector. Through 10 Hz machine vision optical tracking with nested 200 Hz tip/tilt adaptive optics stabilisation, we corrected for pointing errors and atmospheric turbulence to maintain robust single mode fiber coupling, resulting in an uninterrupted 100 Gbps optical data link while tracking at angular rates of up to 1.5 deg/s, equivalent to that of spacecraft in low earth orbit. With the greater data capacity of coherent communications and compatibility with extant fiber-based technologies being demonstrated across static links, ground-to-low earth orbit links of Terabits per second can ultimately be achieved with capable ground stations.

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“…This can be accomplished with traditional AO 15,29 , or with novel "passive" methods such as photonic lanterns 30 or multi-plane light conversion 31 . In combination with atmospheric phase-stabilisation technology [32][33][34] , such a deployable optical terminal could even facilitate secure ground-to-LEO continuous variable quantum key distribution (CV-QKD) 35 .…”

Section: Resultsmentioning

confidence: 99%

Demonstration of 100 Gbps Coherent Free-Space Optical Communications at LEO Tracking Rates

Walsh

¹

,

Karpathakis

²

,

McCann

³

et al. 2022

Preprint

0

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Free-space optical communications are poised to alleviate the data-flow bottleneck experienced by spacecraft as traditional radio frequencies reach their practical limit. While enabling orders-of-magnitude gains in data rates, optical signals impose much stricter pointing requirements and are strongly affected by atmospheric turbulence. Coherent detection methods, which capitalize fully on the available degrees of freedom to maximize data capacity, have the added complication of needing to couple the received signal into single-mode fiber. In this paper we present results from a coherent 1550 nm link across turbulent atmosphere between a deployable optical terminal and a drone-mounted retroreflector. Through 10 Hz machine vision optical tracking with nested 200 Hz tip/tilt adaptive optics stabilisation, we corrected for pointing errors and atmospheric turbulence to maintain robust single mode fiber coupling, resulting in an uninterrupted 100 Gbps optical data link while tracking at angular rates of up to 1.5 deg/s, equivalent to that of spacecraft in low earth orbit. With the greater data capacity of coherent communications and compatibility with extant fiber-based technologies being demonstrated across static links, ground-to-low earth orbit links of Terabits per second can ultimately be achieved with capable ground stations.

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“…The target acquisition and tracking, amplitude stabilization, and phase stabilization systems, and phase correction process, demonstrated here provide the basis for stabilized free-space optical frequency transfer that will enable high-precision geopotential measurements via a flying platform which will lead to significant advances in geodesy, geology and fundamental physics experiments. This technology also has applications in free-space optical communications [31] and free-space quantum key distribution [32,33].…”

Section: Discussionmentioning

confidence: 99%

Optical Frequency Transfer for Geopotential Difference Measurements via a Flying Drone

Dix-Matthews¹,

Gozzard²,

Walsh³

et al. 2022

Preprint

0

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<p>Geopotential and orthometric height differences between distant points can be measured via timescale comparisons between atomic clocks. Modern optical atomic clocks have residual instabilities on the order of 10^-18}, allowing height differences of around 1 cm to be measured. Frequency transfer via free-space optical links will be needed for measurements where linking the clocks via optical fiber is not possible, but requires line of sight between the clock locations, which is not always practical due to local terrain or over long distances. We present an active optical terminal, phase stabilization system, and phase compensation processing method robust enough to enable optical frequency transfer via a flying drone, greatly increasing the flexibility of free-space optical clock comparisons. We demonstrate a residual instability of 2.5x10^-18 after 3 s of integration, corresponding to a height difference of 2.3 cm, suitable for applications in geodesy, geology, and fundamental physics experiments.</p>

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Ultra-Wideband Free-Space Optical Phase Stabilization

Cited by 13 publications

References 24 publications

Demonstration of 100 Gbps coherent free-space optical communications at LEO tracking rates

Demonstration of 100 Gbps coherent free-space optical communications at LEO tracking rates

Demonstration of 100 Gbps Coherent Free-Space Optical Communications at LEO Tracking Rates

Optical Frequency Transfer for Geopotential Difference Measurements via a Flying Drone

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