The Atmospheric moNitoring to Assess the availability of Optical LInks through the Atmosphere (ANAtOLIA) is a station developed in the framework of a project funded by the European Space Agency which aims to ground-sites selection and assess their availabilities for optical links through the atmosphere. In addition to cloud cover, space-to-ground optical communications are limited by aerosols and atmospheric turbulence. Therefore, we are developing in the framework of the ANAtOLIA project, an innovative and efficiency instrumentation and studies to specify, accurately measure, analyze, characterize, and ultimately predict critical atmospheric parameters for the purposes of the selection of the Optical Ground Station (OGS) sites and the evaluation of their availability. The main objectives of ANAtOLIA project are to design, manufacture, procure and assembly a self-standing and autonomous ground support equipment, comprising cloud, aerosol and turbulence monitoring to deliver precise measurements of the atmosphere transmission. Then, to install and commission of these atmosphere monitors at selected ground locations in ESA member states or in their vicinity and to record continuously local cloud, aerosol information and atmospheric turbulence conditions for 24 months. The last objective is to correlate these local ground measurements with data available from other sources of atmospheric conditions. The main goal of these correlations is to improve knowledge of the optical link availability for selected OGS locations and to carry out a long-term validation of the optical link availability prediction methods. ANAtOLIA is a compact 24h mobile station consisting of the Generalized Monitor of Turbulence (GMT), the Reuniwatt Sky Insight camera and the Cimel photometer CE318-T.
Optical feeder links (OFL) are expected to become part of future Very High Throughput Satellite (VHTS) systems in response to the growing demand for higher capacity and lower costs. H2020 VERTIGO (Very High Throughput Satellite Ground Optical Link) project was set to prove key optical communication technologies and to address: 1) Throughput increase with high spectral and power efficiencies. 2) Higher optical power generation and delivery. 3) Atmospheric turbulence mitigation by optical and digital processing. Transmit and receive optical communication models were developed in rack units for assessing, in laboratory and outdoor trials, their intrinsic performance, robustness against atmospheric turbulence and compatibility with other technologies. The models for 25 Gbps OOK/DPSK and RF analog modulation with optically pre-amplified direct or differential detection are reported with the achieved performance. An atmospheric channel emulator fed with time series established by simulations was used to mimic the propagation losses and fading of the optical signal coupled into the receiver. Both the downlink and uplink under weak or strong turbulence were emulated. For digital transmission experiments, the performance metrics include BER curves, detection sensitivity and power penalty. State-of-the-art sensitivities were achieved especially under 25 Gbps DPSK. For RF analog transmission, the performance metrics were constellation diagrams and Error Vector Magnitude (EVM) measured for various modulations from QPSK to 64-QAM. Are reported the results of optical transmission experiments first performed in the laboratory under static and dynamic propagation channels, then in the outdoor trial successfully carried out in July between Jungfraujoch and Zimmerwald in Switzerland.
ANAtOLIA (Atmospheric moNitoring to Assess the availability of Optical LInks through the Atmosphere) is a project funded by the European Space Agency and aims to ground-sites selection and assess their availabilities for optical links through the atmosphere. In addition to cloud cover, space-to-ground optical communications are limited by aerosols and atmospheric turbulence. Therefore, we are developing in the framework of the ANAtOLIA project, an innovative and efficiency instrumentation and studies to specify, accurately measure, analyze, characterize, and ultimately predict critical atmospheric parameters for the purposes of the selection of the OGS (Optical Ground Station) sites and the evaluation of their availability. The main mission objectives of ANAtOLIA are to design, manufacture, procure and assembly a self-standing and autonomous ground support equipment, comprising cloud, aerosol and turbulence monitoring to deliver precise measurements of the atmosphere transmission. Secondary study goals are to install and commission of these atmosphere monitors at selected ground locations in ESA member states or in their vicinity and to record continuously local cloud, aerosol information and atmospheric turbulence conditions for 24 months. The last objective is to correlate these local ground measurements with data available from other sources of atmospheric conditions. The main goal of these correlations is to improve knowledge of the optical link availability for selected OGS locations and to carry out a long-term validation of the optical link availability prediction methods. This compact 24h mobile station consists of the Generalized Monitor of Turbulence (GMT), Reuniwatt Sky Insight camera and Cimel CE318-T.
To concurrently cope with the scarcity of RF frequency bands, the growing capacity demand and the required lower cost of the ground segment, Very High Throughput Satellites systems must rely on new technical solutions. Optical feeder links are considered as a promising alternative to surpass classical RF technology, offering assets inherent to optical technologies (large bandwidth, no frequency regulation, low beam divergence, components availability). Nevertheless the potential of this technology shall not conceal the remaining challenges to be overcome to make it relevant for operational missions : clouds, turbulence, power generation and high efficiency modulations. VERTIGO (Very High Throughput Satellite Ground Optical Link) is a 3-year H2020 project funded by the European commission and started mid-2019 focusing on the optical link itself regardless of site diversity aspect and aiming at demonstrating in a ground demonstration required technologies to implement very high capacity optical feeder links. In particular, VERTIGO is built on 3 pillars each addressing a key issue for the implementation of optical feerder links: 1) Throughput increase through the use of advanced schemes with high spectral and power efficiency compared to current modulations used in space, as well as RF-over-Fiber approach. 2) High optical power generation to close the demanding link budgets by developing on-board and ground means to raise the transmitted optical power, not only based on amplifier power increase, but also on incoherent/coherent power combining. 3) Opto-mechanical and digital techniques for the mitigation of atmospheric propagation impairments, to make full use of throughput and power increases. Several demonstrations in-flight or on-ground already demonstrated separately key aspects (atmospheric propagation and impairments mitigation techniques, modulation format, high power…), for the implementation of optical (feeder) links. These aspects are closely linked since the solutions to each of them are necessary but not sufficient to allow for high throughput transmissions. VERTIGO concept is to address each key issue with at least one solution and to combine them in an unprecedented manner. To reach these objectives, VERTIGO will lean on a highly skilled consortium composed of : CREONIC, ETH Zürich, Fraunhofer HHI, Gooch and Housego, Leo Space Photonics RD, ONERA, Thales Research and Technology, Thales Alenia Space in France and Switzerland. This paper will present the VERTIGO project and its status.
This paper reports on the assessment of the communication performance of DPSK- and OOK-based free-space optical (FSO) links in satellite-based applications, including LEO downlinks, LEO inter-satellite links, and feeder links for GEO Satellites. The performance is assessed by means of simulations as well as transmission experiments at 10 Gbps. The impact of optical filter bandwidth, optical delay-line-interferometer accuracy, frequency offset between transmitter laser and receiver, is quantified. OOK performance critically depends on transmitter extinction ratio, and proves robust to Doppler-induced frequency offsets. DPSK is sensitive to any laser wavelength drift and offset with the DLI response. Nevertheless, compensation of this drift is considered manageable, making it possible to maintain the 3dB advantage of DPSK vs. OOK in practical use conditions.
KEYWORDS: Laser applications, RF photonics, Free space optics, Laser development, Free space optical communications, Frequency conversion, High power lasers, Telecommunications, Satellites, Laser damage threshold
This article reports the development of 200-mW 1.55-μm DFB laser module with RIN below -162 dB/Hz which are well suited for microwave photonics or free space optical communication applications. Specific design has allowed reaching high power (>300 mW), low noise and high spectral purity laser chip. The chip has been packaged in Butterfly module optimized for reducing the module power consumption. DFB laser module system validations have been done on three laboratory test-beds representative of target applications, namely high-frequency optical LO distribution, photonic RF frequency conversion, and free space optical communication links.
Since several years, perspectives and assets offered by photonic technologies compared with their traditional RF counterparts (mass and volume reduction, transparency to RF frequency, RF isolation), make them particularly attractive for space applications [1] and, in particular, telecommunication satellites [2]. However, the development of photonic payload concepts have concurrently risen and made the problem of the ability of optoelectronic components to withstand space environment more and more pressing. Indeed, photonic components used in such photonic payloads architectures come from terrestrial networks applications in order to benefit from research and development in this field.
This paper presents some results obtained in the frame of an ESA-funded project, carried out by Thales Alenia Space France, as prime contractor, and Alter Technology Group Spain (ATG) and Universidad Politecnica de Madrid (UPM), as subcontractors, one objective of which was to assess commercial high frequency optical intensity modulators for space use through a functional and environmental test campaign. Their potential applications in microwave photonic sub-systems of telecom satellite payloads are identified and related requirements are presented. Optical modulator technologies are reviewed and compared through, but not limited to, a specific figure of merit, taking into account two key features of these components : optical insertion loss and RF half-wave voltage. Some conclusions on these different technologies are given, on the basis of the test results, and their suitability for the targeted applications and environment is highlighted.
Among the different optical modulator technologies available such as polymer, III-V semiconductors, Silicon, the well-known Lithium Niobate (LN) offers the best trade-off in terms of performances, ease of use, and power handling capability.
Photonics is progressively transforming from a highly- focused technology applicable to digital communication networks into a pervasive “enabling” technology with diverse non-telecom applications. However, the centre of mass on the R&D level is still mostly driven by, and invested in, by stakeholders active in the telecoms domain. This is due to the high level of investments necessary that in turn require a large and established market for reaching break-even and generation of revenues. Photonics technology and more specifically, fibre-optic technology is moving into non-telecom business areas with great success in terms of markets captured and penetration rates. One example that cannot be overlooked is the application of fibre-optics to industrial applications, where double-digit growth rates are recorded with fibre lasers and amplifiers constantly gaining momentum. In this example, several years of R&D efforts in creating high-power amplification solutions and fibre-laser sources by the telecom sector, were piggy-backed into industrial applications and laser cutting/welding equipment that is now a strong R&D sector on its own and commercially now displacing some conventional free space laser cutting/welding.
Thales Alenia Space has elaborated innovative telecom payload concepts taking benefit from the capabilities of photonics and so-called microwave photonics. The latter consists in transferring RF/microwave signals on optical carriers and performing processing in the optical domain so as to benefit from specific attributes such as wavelength-division multiplexing or switching capabilities.
In the last decade, Thales Alenia Space has put significant research effort in photonic technologies for satellite applications, with the objective to provide telecom payload systems with enhanced functionality, higher performance and lower costs.
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