EPLO: Free-space optics emulator for satellite ground links
Résumé
This paper presents the first results of the EPLO
project (Free-space optical Propagation test bench mimic),
dedicated to the modelling and emulation of the atmospheric
effects on a laser link used for ground-satellite communication.
In order to test different modulation waveforms and their
robustness to tropospheric turbulence, an experimental bench
has been developed to reproduce the front phase deformation
and the effect of beam spreading. This emulator generates
various scenarios of turbulence based on holographic methods.
It includes a beam wander effect, as well as amplitude
scintillation modelling and phase deformation. The turbulence
patterns driving the bench are calculated using the Rytov
approximation with extended Kolmogorov spectrum. Based on
this approximation, time series are generated from scintillation
indices, beam wandering, beam spreading, phase variation, and
the dynamics of the temporal evolution. Those effects are
emulated by a DMD (digital micro-mirror device) using Lee
holographic methods. A TILBA-ATMO (Cailabs) is
implemented in the reception chain. Based on Cailabs’ Multi-
Plane Light Conversion (MPLC) technology, TILBA-ATMO
allows the signal to be coupled into a single-mode fiber whilst
correcting the effects of atmospheric turbulence. This paper
presents the first efficiency results of this experimental setup on
amplitude and phase deformations: this allows us to simulate
and study wave front deformation when the laser propagates
through the troposphere. By coupling the bench with a single
mode fiber, EPLO will allow a complete emulation of an end-
to-end optical link.