9 research outputs found
Pre-correction Adaptive Optics performance of a 10 km Laser Link
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
Pre-distortion adaptive optics for optical feeder links: simulations and performance analyses
Optical feeder links offer immense utility in meeting future communication demandsâhowever, atmospheric turbulence limits their performance. This work targets this challenge through analyses of a bidirectional free-space optical communication (FSOC) link that incorporates pre-distortion adaptive optics (AO) between the next-generation optical ground station at the German Aerospace Center (DLR) Oberpfaffenhofen and the laser communications terminal on Alphasatâa satellite in geostationary orbit (GEO). The analyses are performed via end-to-end Monte Carlo simulations that provide realistic performance estimates of the bidirectional FSOC link for a GEO feeder link scenario. We find that applying pre-distortion AO reduces the total uplink losses of the bidirectional FSOC link by up to 10â
dB and lessens the scintillation at the GEO satellite by an order of magnitude. Moreover, applying pre-distortion AO eases the link budget requirements needed for maintaining 99.9% link uptime by as much as 20-40â
dB, while its use with a laser guide star shows an additional performance improvement of up to 8â
dB. These findings demonstrate the desirability and feasibility of utilizing pre-distortion AO for the realization of optical feeder links
GroundâtoâGEO optical feeder links for very high throughput satellite networks: Accent on diversity techniques
This paper studies the use of optical feeder links in very high throughput satellites (VHTS) networks with emphasis on gateway diversity techniques to mitigate the inherent propagation losses in optical frequencies. Focusing on a GEO scenario, the paper considers a systemâwide approach investigating various challenges of optical feeder links. These include transmission schemes amenable for transparent onâboard processing, optical channel models taking into account blockage by clouds and fading caused by atmospheric turbulence in addition to complexity of onâboard and onâground processing. The channel models are then used to dimension the ground segment towards ensuring a given availability percentage (e.g., 99.9%). The channel model and payload complexity further influence the choice of link layer techniques used for counteracting fading due to atmospheric turbulence in the absence of blockage. An elaborate endâtoâend simulator incorporating the proposed channel models capturing the nuances of various processing blocks like opticalâelectrical conversion is developed. The system performance results provide interesting insights and a framework for assessing the feasibility and advantages of optical feeder links in VHTS systems
Pre-distortion adaptive optics for optical feeder links: simulations and performance analyses
Optical feeder links offer immense utility in meeting future communication demandsâhowever, atmospheric turbulence limits their performance. This work targets this challenge through analyses of a bidirectional free-space optical communication (FSOC) link that incorporates pre-distortion adaptive optics (AO) between the next-generation optical ground station at the German Aerospace Center (DLR) Oberpfaffenhofen and the laser communications terminal on Alphasatâa satellite in geostationary orbit (GEO). The analyses are performed via end-to-end Monte Carlo simulations that provide realistic performance estimates of the bidirectional FSOC link for a GEO feeder link scenario. We find that applying pre-distortion AO reduces the total uplink losses of the bidirectional FSOC link by up to 10â
dB and lessens the scintillation at the GEO satellite by an order of magnitude. Moreover, applying pre-distortion AO eases the link budget requirements needed for maintaining 99.9% link uptime by as much as 20-40â
dB, while its use with a laser guide star shows an additional performance improvement of up to 8â
dB. These findings demonstrate the desirability and feasibility of utilizing pre-distortion AO for the realization of optical feeder links