As global demand for data rates and connectivity grows, telecom operators predict congestion in commonly used radio frequency bands in the short term, and see optical ground-satellite communications as a key solution for tomorrow’s very high throughput telecommunications. However, despite their potential, optical communications have to overcome a serious obstacle: atmospheric turbulence that greatly disturbs signal transmission, and thus requires the development of mitigation techniques.
Adaptive Optics (AO) is one of the most promising mitigation strategies to reduce the negative effects of the atmosphere on the optical links; it consists of compensating in real time the effects of the turbulence on the optical signal, by commanding a corrector element or deformable mirror with the turbulence information measured by the wavefront sensor. In case of optical communications, the adaptive optics systems need to cope with a large diversity of turbulence conditions and handle the strong scintillation induced by strong perturbations. In particular, the design of the wavefront sensor will be questioned: even in the case of a simple Shack-Hartmann sensor, many questions remain about its behaviour and its optimization for telecoms, since in presence of strong scintillation several of its sub-apertures may become saturated or extinct.
The purpose of this project is to quantify the impact of these strong perturbations on the performance and robustness of the AO-compensated optical telecommunications system. The core of the thesis will be the development of a simplified model that predicts accurately the signal statistics regarding AO configuration and turbulence conditions, in presence of both weak and strong perturbations. This model will serve to characterize and optimize the WFS behaviour and to analyse a potential tip-tilt retrieval method using laser guide stars, both under strong and weak scintillation conditions.
This is a PhD project supervised by Dr Aurélie Montmerle Bonnefois and Dr Jean-Marc Conan (The French Aerospace Lab ONERA) and advised by Dr Noelia Martinez (ANU) and Prof Celine D’Orgeville (ANU). The PhD project could take place either at the ANU or at ONERA. The student will be able to work on numerical models (simplified and end-to-end) and test the outcome of these studies experimentally in the laboratory; the student may be based at ONERA or at the ANU, and conditions permitting, will have the opportunity to undertake a research internship at the other location.
For more information about research at ONERA, visit: https://www.onera.fr/en/research-at-onera
REQUIRED SKILLS: Postgraduate students are encouraged to contact the project team and inquire about current and potential research projects. Prior experience in at least two of the following disciplines is required: physics, computer science, optical communications, space engineering, instrumentation.