Description
The objective of this activity is demonstrate reliable high data rate optical transmission through the atmosphere (>100Gbps) in a scenario representative (in terms of link attenuation and optical turbulence) of an optical link between a telecom satellite and an Optical Ground Station for elevation angles down to 5deg.
Targeted improvements: Improve the service quality and availability of highdata rate optical links through the atmosphere (e.g., direct to Earth optical downlinks, optical feeder links) due to strong atmospheric turbulence effects for elevations angles down to 5deg / scintillation index >1.
Description:
Propagation of laser beams through turbulent media degrades the characteristics of the optical signal (i.e. phasefront distortion, scintillation, beam spreading, beam wandering). The degradation of the optical beam is significantly larger in the uplink than in the downlink, due to fact that the turbulence is much closer to the ground transceiver than to the space transceiver. Countermeasures on the transmitted and the received optical communications beams are necessary in order to improve the link quality (i.e., BER), and to increase the link availability and the link communications time (i.e., reduce the minimum elevation angle).
Adaptive Optics is typically used to correct the atmospheric induced phasefront distortions on the (received) optical downlink, and hence, to increase the coupling efficiency into a single mode fibre, or equivalently, the mixing efficiency with an optical local oscillator. Such countermeasure has been experimentallyproven for weak and medium turbulence (typically for elevation angles > 20-30deg). However, to maximize the link quality, the link availability and the link communications time, countermeasures to compensate for strong atmospheric turbulence (elevation angles down to 5deg) in the downlink are to be developed and demonstrated. In this activity, the Contractor shall critically review the outcomes and conclusions of the previous study SL.013.
After a trade-off of the possible solutions (e.g. advanced wavefront sensors and high spatial resolution correction actuators less sensitive to scintillation effects, novel large area / high bandwidth / low noise detectors, adaptive number of WDM channels, etc.), the Contractor shall select the preferred option(s) for demonstration in a scenario representative (in terms of link attenuation and optical turbulence) of a high data rate optical link (>100Gbps) between a telecom satellite and an Optical Ground Station for elevation angles down to 5deg. System scalability shall be implemented by means of wavelength division multiplexing (WDM).
The performances of the optical link shall be tested for a sufficiently long time period under different atmospheric turbulence conditions (to assess day time / night time turbulence changes and seasonal turbulence variations).