Investigation on adaptive optics performance from propagation channel characterization with the small optical transponder

Abstract

In order to address the high throughput requested for both downlink and uplink satellite to ground laser links, Adaptive Optics (AO) has become a key technology. While mature, application of this technology to satellite to ground telecommunication faces however difficulties such as higher bandwidth, optimal operation for a wide variety of atmospheric conditions (daytime and nighttime) with potentially low elevations that might severely affect wavefront sensing because of scintillation. To address these specificities an accurate understanding of the origin of the perturbations is required, as well as operational validation of AO on real laser links. We report here on a Low Earth Orbiting (LEO) microsatellite to ground downlink with AO correction. We discuss propagation channel characterization based on Shack-Hartmann WaveFront Sensor (WFS) measurements. Fine modelling of the propagation channel is proposed based on multi-Gaussian model of turbulence profile. This model is then used to estimate the AO performance and validate the experimental results. While AO performance is limited by the experimental setup , it proves to comply with expected performance and further interesting information on propagation channel is extracted. These results shall help dimensioning and operating AO systems for LEO to ground downlinks.

Protecting the entanglement of twisted photons by adaptive optics

“…Whereas without AO compensation both concurrence and trace rapidly decay with increasing turbulence strength, even minimalistic (tip/tilt) correction allows for an enhancement of the latter quantities by a factor of two to four. These results suggest that state of the art AO systems [35], able to correct higher order aberrations of the wave front, bear the potential to enhance these factors still further -up to the almost complete restoration of entanglement and an increase of the trace by a factor between five and thirteen, in the ideal case.…”

Laser communication experiments between Sota and Meo optical ground station

“…AO bench at 976nm 1,5m pupil The ODISSEE Adaptive Optics bench has been used on SOTA signal for the two passes of 21 th of July 2015 and 15 th of October 2015. The analysis of the pass of July has already been published in [11]. The measured performance of the AO was compared to the theoretical one taking into account the characteristics of the bench, the pupil size and the turbulence conditions.…”

“…A great opportunity was offered to CNES to take part of the SOTA international campaign [2] that has permitted to collect real turbulence profiles. The analysis of the pass of the 21 th of July 2015 has been already published [11]. The signal was collected using the Shack-Hartmann wavefront sensor (SH-WFS) of the ODISSEE Adaptive Optics Bench.…”

“…The exploitation of the temporal spectra (PSD) of the wavefront decomposed onto Zernike polynomials enables to retrieve the parameters of C n ² profile models. In [11] a Multi-Gaussian (MG) C n ² profile has been used to fit the data recorded in July. This MG profile is plotted in Fig.…”

Evaluation of communication performance for adaptive optics corrected geo-to-ground laser links

“…The resulting channel impairments can be significantly reduced by the use of appropriate adaptive optics (AO) compensation at the expense of potentially complex and expensive systems if very high stability of the injection is required. Feasibility demonstrations of AO correction were recently reported in the US [1] and France [2] with Low Earth Orbit (LEO) satellites, and in Germany with GEO satellites [3]. To reduce the loss in useful information and to relax by the same way the specifications and cost of AO systems, numerical techniques such as error-correcting codes have to be considered as well.…”