Free space laser communications and atmospheric transmission conference reports

The technical discussions on Free-Space Laser Communication and Atmospheric Propagation held at the Photonics West show in San Jose, California, USA from February 15-18, 2016, by the International Association of Optoelectronics Engineering (SPIE) SPIE collated into the 9739th volume conference proceedings, newspaper summary part of the conference Abstract: 1, article written by RW Kingsbury et al., Planet Labs Inc., USA, entitled "Implementation and Verification of a CubeSat Laser Transmitter". This article presents the implementation and verification of a CubeSat microsatellite satellite laser transmitter. Its main oscillator power amplifier (MOPA) is designed to: use a directly modulated laser diode and a commercially available fiber amplifier to generate an optical signal with a wavelength of 1550 nm and an average power of 200 mW. The prototype design produces a high-fidelity M-PPM waveform (M = 8-128) with a target data rate greater than 10 megabits per second while meeting the 8W power-distribution constraints. The authors also present an implementation of an avalanche photodiode (APD) receiver whose measured transmit-to-receiver performance is within 3 dB of the theoretical value. With loopback, this compact receiver design provides built-in self-test and calibration capabilities and supports incremental on-rail testing of this receiver design. 2. N. Védrenne et al., National Aeronautics and Astronautics Center, France, published an article entitled "Adaptive Optical Systems for High Data Rate Satellite to Earth Laser Links". To match the increasing demand for high data rates between high-altitude platforms and the ground, the authors studied the free-space optical links. Part of the growing interest comes from the possibility of making full use of technically mature fiber optic components, namely the need to inject the received wave into a single-mode fiber. In order to reduce the ground terminal injection loss, the use of adaptive optics (AO) was studied. This adaptive optics system must operate under a wide variety of turbulent conditions: limitations of the optical ground station (which may be detrimental to atmospheric turbulence), such as at daytime and at night, at potentially very low altitudes (for LEO satellites). In astronomy, the amount optimized is the average Strierby, and in contrast to free-space communications, the statistical and temporal characteristics of injection loss must be considered. The results of some of the corrections were also explored here by numerical simulations of GEO (geostationary Earth orbit) and LEO (low Earth orbit) earth links. 3. Amnon G. Talmor et al. From Facebook Corporation of the United States published an article titled "Biaxial Stent for Air-Space and Earth-Space Laser Communication in Stratosphere". A hemispherical + 30 ° observation field and a low-drag biaxial gimbal were designed for bi-directional links between the high altitude platform (HAPS) and the ground, and for space-space communication between such high altitude platforms. prototype. The gimbal includes two servo-controlled non-orthogonal pitches on the azimuth axis and an inner quick-turn mirror for fine-tuning the field. The design includes a pitch-class 7.5 cm diameter refracting telescope with output mirrors that fold between the double mirrors to form a double-mirror miniature retract path fixed at azimuth. In exchange for a variety of universal stent configuration, before finalizing this meets the requirements of the program. The design chosen utilizes a carbon fiber and magnesium composite structure, driven by a custom servomotor and commutated via an optical encoder. The azimuth stage is electrically connected to the stationary base by a slip ring, while the pitch stage is made of a passive optical element. The two shafts are aligned with angular contact double bearings of custom steel-based ceramic materials and are controlled by an embedded electronics equipped with a soft-hard bonded plate structure. Finite element analysis (FEA) shows that the design is mechanically robust over the temperature range of + 60 ° C to -80 ° C and the first mode of natural frequency is above 400 Hz. The gimbaled prototype has a total mass of 3.5 kg and includes an internal optical bench that contains fast steering mirrors (FSMs) and tracking sensors. The next version of this gimbal will weigh less than 3.0 kg during the prototype phase. 4. Andrew S Fletcher and others at the Massachusetts Institute of Technology's Lincoln Laboratory published an article titled "Propagation Simulation Results of Narrow Beam Submarine Laser Communication." Because submarine propagation physics is different from air, communication links through seawater can be challenging. Although undersea media is challenging, blue-green wavelengths of submarine optical communications can still achieve high data rates (megabits to Gigabit per second). Absorption and scattering of seawater attenuate the optical signal, and the waveform is distorted by intensive multipath scattering. Exponential propagation losses and time-domain spreading due to multipaths can limit the achievable link distances and data rates. In this paper, the authors describe Monte Carlo simulations of seafloor scattering and absorption channels. The authors simulated the level of photon signal attenuation, the spatial photon distribution, the time to reach the statistics, and the statistical arrival angle in various laser communications scenarios after passing clear and turbid water environments. The simulation results can be used for design choices for subsea optical communication systems, and in particular illustrate the advantages of narrow beam lasers over wide beam methods such as LED light sources. The simulated pupil plane and focal plane photon arrival distribution make beam-tracking technology possible, and the beam-tracking technique can be used to solve the alignment problem even in high-scattering docklands waters. Laser communication using collimated beams maximizes the number of photons transmitted through the scattering medium, and spatial and temporal filters can be used to reduce waveform distortion and background interference.