Pre-correction adaptive optics performance for a 10 km laser link

Abstract

For the next generation of very high throughput communication satellites, free-space optical (FSO) communication between ground stations and geostationary telecommunication satellites is likely to replace conventional RF links. To mitigate atmospheric turbulence, TNO and DLR propose Adaptive Optics (AO) to apply uplink pre-correction. In order to demonstrate the feasibility of AO pre-correction an FSO link has been tested over a 10 km range. This paper shows that AO pre-correction is most advantageous for low point ahead angles (PAAs), as expected. In addition, an optimum AO precorrection performance is found at 16 AO modes for the experimental conditions. For the specific test site, tip-tilt precorrection accounted for 4.5 dB improvement in the link budget. Higher order AO modes accounted for another 1.5 dB improvement in the link budget. From these results it is concluded that AO pre-correction can effectively improve highthroughput optical feeder links.

First Experimental Demonstration of Adaptive Optics Pre-Compensation for GEO Feeder Links in a Relevant Environment

“…Several experiments have been recently reported that demonstrated the technology feasibility for pre-compensation. These demonstrations took place either on a short path [1] or on a 10 km long horizontal path [2]. In both cases the representativeness of the line of sight is limited.…”

QKD optical ground terminal developments

“…For this purpose TNO's optical feeder link adaptive optics (OFELIA) breadboard has been used. This experimental set-up has been built to test and verify the performance of Adaptive Optics pre-correction for optical feeder links [13,14]; see also Figure 6. It consists of an AO system, a Tx and Rx channel, and a focus camera to verify beam quality.…”

“…The presented OGT design is primarily driven by the BB84 protocol with a satellite service node orbiting at LEO. The BB84 approach is relativemature, for which subsystems have been demonstrated in laboratories or in relevant environments and even a comparable full end-to-end system has already been demonstrated [14,15]. With an overpass time of (only) a few minutes, a LEO satellite based service could offer near global coverage.…”

“…We have several space terminal developments [9,10], including optical telescopes, coarse pointing assemblies, and fast steering mirrors [11,12] to limit pointing errors. For ground terminal developments, adaptive optics systems are being developed to improve the fiber coupling in downlinks and to pre-correct turbulence effects in uplinks [13,14]. High power beam multiplexers are being developed for the very high throughput Earth-GEO satellite cases [15].…”

Optimisation of the pre-compensation phase for GEO-feeder optical uplinks

“…While classic AO pre-compensation relying on the downlink phase measurement is the most mature technique, having led to several experimental demonstration on the field , [1][2][3] several concepts to address the anisoplanatism issue can be found in the literature. The most efficient method would be to access to a measurement at PAA, for instance from a laser guide star (LGS) as originally proposed by Tyson.…”