Agricultural mechanization in Ethiopian: Experience, status and prospects

Agricultural Mechanization deals with the use of any mechanical aid in agricultural production. These mechanical aids could be simple hand tools, animal drawn implements or sophisticated mechanically powered agricultural machines. The source of energy ranges from humans, animals to engine or electrical power. Generally these are categorized as hand tool,, animal and mechanically powered technology. The productivity of each level depends on the power source. Humans being inefficient one can hardly cultivate a hectare of land per season, where as animal powered technology is of no use beyond three hectares where as mechanical powered technology is good enough to cultivate a minimum of 40 hectares even in sub moist zones where the window of operation time does not exceed 15 days. The three levels of mechanization have existed in this country for many years now. During Imperial Ethiopia, there were big farms operating as share companies, where mechanically powered technologies were used in areas like Dubti, which were highly productive and produced competitive product in the then world market. During the time of the Derg and now most of the big farms are not producing to the level of the national average. Today you hear in the news that entrepreneurs have cleared the land, but not have started production yet. The mode of land clearing was not systematic and did not take precaution in terms environmental and social safe guards. It is not only the level of mechanization, but the discipline commitment in the mode of production that guarantees the sustainable production and productivity of the land to meet today’s need and the requirement of tomorrow’s generation. Land is a limited resource, besides the competition for land from the other economic sectors is paramount, despite the increasing population and the number of mouths to feed. Under these circumstances it is only a knowledge based agricultural mechanization system, where precision and efficiency are the pillars that will operate under this paradox of feeding increasing population in a situation of dwindling resource base

Investigation of advanced control for adaptive optics in free-space optical communication

Free-Space Optical (FSO) communication can play an important role in meeting the demands of future high throughput and high data rate communication applications. However, atmospheric turbulence induced effects degrade the performance of FSO communication links resulting in high volume data losses. Adaptive Optics (AO) can be used to mitigate the effects of atmospheric turbulence in FSO links. A key challenge is the fact that turbulence scenarios in FSO links are stronger and FSO links are expected to remain operational in all conditions. This requires a robust AO controller that can cope with the more extreme turbulence. In this work, the design and simulation of one such advanced controller based on Linear Quadratic Gaussian control (LQG) is presented. The operation of the controller is demonstrated with an end-to-end simulation. The simulation uses multi-layer phase screens for representing the turbulent atmosphere and angular spectrum propagation for accuracy. We present here the performance of the AO controller through an analysis of the Strehl ratio, the fiber coupling efficiency and the power scintillation index on the fiber achieved

Alternative passive fiber coupling system based on multi-plane light conversion for satellite-to-ground communications

Global coverage of internet access is essential for digitalization in society, becoming a disruptive technology in industry, education or political participation for example. Satellite communications is a complementary approach to the terrestrial fiber network, which can provide world-wide coverage with few satellites in geostationary orbit or with low-earth-orbit constellations. Optical wavelengths offer multiple THz of available spectrum that can be used to connect satellites to the ground network with high-throughput links, solving the radiofrequency bandwidth bottleneck, without regulations. Cloud covereage and atmospheric turbulence are the main challenge in guaranteeing the same availability as in terrestrial fiber-based systems. While the former can be addressed by site diversity, for the latter, other mitigation strategies are required. Adaptive optics is a common approach to correct for atmospheric phase distortions and ensure stable fiber coupling. However, this approach requires a relatively complex active setup and therefore a collaboration between DLR Institute of Communications and Navigation and Cailabs has been formed to investigate alternative passive solutions for low-complexity ground stations. Coupling into multimode fibers does not require adaptive optics due to the large fiber core, however the coupled signal is distributed into multiple fiber-modes and is therefore incompatible with standard telecommunications components. Cailabs Multi-Plane Light Conversion (MPLC) technology overcomes this issue, selectively demultiplexing the fibermodes into single-mode fibers. Here, DLR's adaptive optics system and the MPLC technology in a turbulence-relevant environment for GEO communications are compared, investigating the advantages of the MPLC approach for compensating strong turbulence. This paper presents an overview of the measurement setup and analyzes the single-mode fibers outputs of the spatial demultiplexer and the measured phase-distortions from a wavefront sensor

Optical technologies for very high throughput satellite communications

Broadband internet access has become a vertex for the future development of society and industry in the digital era. Geostationary orbit (GEO) satellite can provide global broadband coverage, becoming a complementary solution to optical fiber network. Low-earth-orbit (LEO) constellations have been proposed in the last years and they may become a reality soon, but still based on radiofrequency for the ground-to-satellite links. Optical technologies offer multiple THz of available spectrum, which can be used in the feeder link. The DLRs Institute of Communications and Navigation has demonstrated Terabit-per-second throughput in relevant environment for GEO communications, in terms of the turbulent channel. In 2016 DLR set the world-record in free-space communications to 1.72 Tbit/s, and in 2017 to 13.16 Tbit/s. Two terminals, emulating the satellite and the ground station have been developed. Bi-directional communications link with single-mode-fiber coupling at both ends was demonstrated. Adaptive optics for the downlink and uplink (pre-distortion) improved the fiber-coupling in downlink and decreased signal fluctuations in uplink. A 80 Gbit/s QPSK system based on digital homodyne reception was also developed, demonstrating the use of coherent communications under strong turbulence conditions. These activities were performed in the frame of two internal DLR projects, THRUST and Global Connectivity Synergy project. Several measurement campaigns took place in the last years in a valley-to-mountain-top test-link. Turbulence has been monitored at both ends and the point-ahead-angle has been emulated by separating the downlink beacon from the receiving aperture. An overview of the system and the main results will be presented