EPLO: Free-space optics emulator for satellite ground links

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.