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Wavefront sensing for terrestrial, underwater, and space-borne free-space optical communications

: Gladysz, Szymon; Zepp, Andreas; Segel, Max; McDonald, Douglas; Bellossi, Raphaël; Lechner, Daniel; Galicia Gasperin, Osvaldo Javier; Stein, Karin


Anguita, Jaime A. (Ed.) ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Laser Communication and Propagation through the Atmosphere and Oceans X : 1-5 August 2021, San Diego, California, United States
Bellingham, WA: SPIE, 2021 (Proceedings of SPIE 11834)
ISBN: 978-1-5106-4506-6
ISBN: 978-1-5106-4507-3
Paper 118340F, 12 S.
Conference "Laser Communication and Propagation through the Atmosphere and Oceans" <10, 2021, San Diego/Calif.>
Fraunhofer IOSB ()
adaptive optics; wavefront sensing; atmospheric turbulence; free-space optical communication

We present several solutions to problems particular to adaptive optics for free-space laser-based communications. Specifically, for scenarios where strong scintillation is present, we have developed a digital, adaptable Shack-Hartmann wavefront sensor, as well as the modal holographic wavefront sensor based on the Karhunen-Loève modes. Additionally, using the same modal basis and optimization algorithms from deep learning, we have improved upon stochastic parallel gradient descent wavefront-sensorless approach. For underwater communications, we have set up a water tank and demonstrated real-time adaptive optics in the visible. For deep-space downlinks, we have investigated several wavefront sensing modalities with respect to their robustness to very low signal-to-background ratios expected during daytime. We also present results of data transmission experiments using coherent modulation over a 400-m double-pass horizontal link.