The LOLA program aims at characterising a 40.000 km optical link through the atmosphere between a high altitude aircraft and a geostationary platform. It opens a new area in the field of optical communications with moving platforms. A complete new optical terminal has been designed and manufactured for this program. The optical terminal architecture includes a specific pointing subsystem to acquire and stabilize the line of sight despite the induced vibrations from the aircraft and the moving pattern from the received laser signal. The optical configuration features a silicon carbide telescope and optical bench to ensure a high thermoelastic angular stability between receive and transmit beams. The communications subsystem includes fibered laser diodes developed in Europe and high performance avalanche photo detectors. Specific encoding patterns are used to maintain the performance of the link despite potential strong fading of the signal. A specific optical link model through the atmosphere has been developed and has been validated thanks to the optical link measurements performed between ARTEMIS and the Optical Ground Station located in the Canarian islands. This model will be used during the flight tests campaign that is to start this summer.
Next generation broadband telecommunication satellites are required to provide very high data throughput using complex multibeam architectures. These high throughput ‘Terabit/s’ Satellites will incorporate payloads with very large quantity of conventional RF equipment, co-axial cables, waveguides, harnesses and ancillary equipment, making the Assembly, Integration and Test (AIT) very complex. Use of ‘RF over Fiber’ and associated photonics equipment can make the process of AIT much simpler with the added benefit of significant reduction in number of payload equipment and inherent payload mass.
In this paper, optical uplink and downlink are studied in order to ensure the feeder link of the next generation of broadband geostationary satellite with capacity around 1Tbps. For such capacity, optical links are commonly based on pre-amplified optical receiver with Single Mode Fiber (SMF) optical amplifier. Adaptive optic systems are necessary to compensate the distortions embedded by the atmospheric turbulences that decrease the injection efficiency of the downlink and the pointing accuracy of uplink. This paper is focused on the performances achievable with a simple system based on a single fine pointing mechanism. Considering a digital optical feeder link that is transparent with respect to the user segment, a promising capacity per satellite of 300GHz is achieved.
Optical links at 1.55μm are envisaged to cope with the increasing capacity demand from geostationary telecom satellite
operators without the need of Radio Frequency (RF) coordination. Due to clouds blockages, site diversity techniques based
on a network of Optical Ground Stations (OGS) are necessary to reach the commonly required link availability (e.g. 99.9%
over the year). Evaluation of the N Optical Ground Station Network (N-OGSN) availability is based on Clouds Masks
(CMs) and depends on the clouds attenuation taken in the optical communication budget link. In particular, low attenuation
of high semitransparent clouds (i.e. cirrus) could be incorporated into the budget link at the price of larger or more powerful
optical terminals. In this paper, we present a method for the calibration of the attenuation at 1.55 μm of high semitransparent
clouds. We perform OGS localization optimization in Europe and we find that the incorporation of thin cirrus attenuation
in the budget link reduces by 20% the number of handover (i.e. switches OGS) and the handover rate. It is also shown that
the minimum number of station required in Europe to reach 99.9% link availability is 10 to 11. When the zone of research
is enlarged the Africa, this number is reduced to 3 to 4.
High data rate communications between satellites request to develop very specific electronic circuits. Very high speed, high current (more than 500 mA peak to peak) and low power consumption laser driver was realized and integrated into a specific low volume and low mass hybrid design. This paper reports also the realization of a complete receiver based on the integration of an Avalanche Photodiode (APD) into a very low noise preamplifier followed by an other hybrid module including a limiter amplifier, a clock recovery and decision circuit. The high voltage DC/DC convertor for the APD is also presented as a third hybrid circuit. Full bit rate is in the range of 622 Mbps. For the receiver, the sensitivity obtained is very closed to the theoretical possibilities. The opto- electronic modules under realization (or realized) are fiber pigtailed, with a single mode fiber on the transmitter side and a multimode fiber on the receiver side which allow their integration into the communication boxes. The present paper gives an overview of the modules development, including the main results, and situates these activities in a more complete realization of optical communication boxes.
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