Michel Sotom

Radiation-resistant erbium-doped-nanoparticles optical fiber for space applications

We demonstrate for the first time a radiation-resistant Erbium-Doped Fiber exhibiting performances that can fill the requirements of Erbium-Doped Fiber Amplifiers for space applications. This is based on an Aluminum co-doping atom reduction enabled by Nanoparticules Doping-Process. For this purpose, we developed several fibers containing very different erbium and aluminum concentrations, and tested them in the same optical amplifier configuration. This work allows to bring to the fore a highly radiation resistant Erbium-doped pure silica optical fiber exhibiting a low quenching level. This result is an important step as the EDFA is increasingly recognized as an enabling technology for the extensive use of photonic sub-systems in future satellites.

Theoretical explanation of enhanced low dose rate sensitivity in erbium-doped optical fibers

A new theoretical framework is proposed to explain the dose and dose-rate dependence of radiation-induced absorption in optical fibers. A first-order dispersive kinetics model is used to simulate the growth of the density of color centers during an irradiation. This model succeeds in explaining the enhanced low dose rate sensitivity observed in certain kinds of erbium-doped optical fiber and provides some insight into the physical reasons behind this sensitivity.

Reconfigurable microwave photonic repeater for broadband telecom missions: concepts and technologies

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.

Towards telecommunication payloads with photonic technologies

In the last decade, Thales Alenia Space has put a lot of its research effort on Photonic Technologies for Space Application with the aim to offer the market satellite telecommunication systems better performance and lower costs. This research effort has been concentrated on several activities, some of them sponsored by ESA. Most promising applications refer to Payload Systems. In particular, photonic payload applications have been investigated through the following two ESA studies: Artes-1 “Next Generation Telecommunication Payloads based on Photonic Technologies” and Artes-5 “OWR – Optical Wideband Receiver” activities.

Optimization and evaluation in space conditions of multi-ghz optical modulators

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.

Multichannel VCSEL-based optical transceiver employing multicore fibers at 6x25 Gbps/fiber (Conference Presentation)

Multicore fiber enables a parallel optic data link in a single optical fiber. Thus, it is an attractive approach to increase the aggregate data throughput and the integration density of the interconnection. nWe developed and demonstrated mid-board optical transceiver modules employing novel multicore fiber pigtails and multicore-optimized optoelectronic engines. The silica fibers having 125 µm diameter and including six graded-index multimode cores enable multi-gigabit interconnects at very short distances. The fiber is compatible with the 850-nm VCSEL technology that has many advantages, such as, the very low power operation and the mature and cost-effective GaAs-based device technology.nThe transceiver incorporates transmitter and receiver subassemblies that are based on the multicore-optimized 850-nm VCSEL and photodiode array chips as well as on the co-designed multichannel VCSEL driver and TIA receiver ICs. All devices are operating up to 25 Gbps/channel and beyond, thus creating a 150 Gbps full-duplex link with the two 6-core fibers. The active areas on the 6-channel VCSEL and PD chips are arranged in a circular array layout that matches the cross-sectional layout of the fiber cores. This allows butt coupling to the fiber cores. The power consumption of the complete link is below 5 mW/Gbps.nThe transceiver was developed to be applicable for harsh environmental conditions, including space. Therefore, for instance, hermetic packaging was applied and both the active devices and the integration structure enable very wide operation temperature range of up to approx. 100 °C.nThis paper will present the technical approach including the basic building blocks and the transceiver module implementation. It will also present the results of the data link performance and some reliability testing.

Comparison of gamma radiation effect on erbium doped fiber amplifiers

Optical amplifiers have many applications in space, such as transmitters, receivers, for satellite telecom, lidars and remote sensing.

Flexible photonic payload for broadband telecom satellites: from concepts to system demonstrators

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.

High-throughput optical inter-board interconnects for next-generation on-board digital transparent processors

The satellite telecommunication sector is continuously facing new challenges. Operators turn towards increasing capacity payloads with higher number of beams and broader bandwidth, in order to cope with exhausting orbital positions and to lower the cost of in-orbit delivery of bit. Only satellites able to provide high data rate connections to numerous users are expected to achieve affordable communication prices. On the other hand, as the telecom market grows and the range of offered services (HDTV, Video On Demand, Triple Play), operators call for more versatile solutions to quickly grasp new markets and to adapt to these evolutions over the average 15 years of a satellite lifetime. Flexible payloads have found an increasing interest for a number of years. Flexibility is considered as a means for a better commercial exploitation of a satellite fleet and a better allocation of resource in response to traffic evolution and/or changing business plans, with potential advantages such as a wider range of applications, less customization for specific missions, increased production runs of equipment, enhancement of reliability, reduction of equipment cost, reduction of program schedules [1]. Flexibility is expected to be offered in spectrum management and frequency plan, in coverage, or in the repeater power allocation. The industry is taking up the challenge both by improving current telecom satellites and offering new payload technology, more flexible and able to address the new markets. From a system integrator perspective, flexibility is as an opportunity to design more generic payloads, that can be customized during or after fabrication only, thus shortening the design-to-manufacturing cycle, and improving the industry competitiveness.

Opto-microwave Butler matrixes based front-end for a multi-beam large direct radiating array antenna

The evolution of broadband communication satellites shows a clear trend towards beam forming and beamswitching systems with efficient multiple access schemes with wide bandwidths, for which to be economically viable, the communication price shall be as low as possible. In such applications, the most demanding antenna concept is the Direct Radiating Array (DRA) since its use allows a flexible power allocation between beams and may afford failures in their active chains with low impact on the antenna radiating pattern. Forming multiple antenna beams, as for ‘multimedia via satellite’ missions, can be done mainly in three ways: in microwave domain, by digital or optical processors: - Microwave beam-formers are strongly constrained by the mass and volume of microwave devices and waveguides - the bandwidth of digital processors is limited due to power consumption and complexity constraints. - The microwave photonics is an enabling technology that can improve the antenna feeding network performances, overcoming the limitations of the traditional technology in the more demanding scenarios, and may overcome the conventional RF beam-former issues, to generate accurately the very numerous time delays or phase shifts required in a DRA with a large number of beams and of radiating elements. Integrated optics technology can play a crucial role as an alternative technology for implementing beam-forming structures for satellite applications thanks to the well known advantages of this technology such as low volume and weight, huge electrical bandwidth, electro-magnetic interference immunity, low consumption, remote delivery capability with low-attenuation (by carrying all microwave signals over optical fibres) and the robustness and precision that exhibits integrated optics. Under the ESA contract 4000105095/12/NL/RA the consortium formed by DAS Photonics, Thales Alenia Space and the Nanophotonic Technology Center of Valencia is developing a three-dimensional Optical Beamforming Network (OBFN) based on integrated photonics, with fibre-optics remote antenna feeding capabilities, that addresses the requirements of SoA DRA antennas in space communications, able to feed potentially hundreds of antenna elements with hundred of simultaneous, orthogonal beams. The core of this OBFN is a Photonic Integrated Circuit (PIC) implementing a passive Butler matrix similar to the structure well known by the RF community, but overcoming the issues of scalability, size, compactness and manufacturability associated to the fact of addressing hundred of elements. This fully-integrated beam-former solution also overcomes the opto-mechanical issues and environmental sensitivity of other free-space based OBFNs.