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"Space communication"
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Overview of deep space laser communication
The deep space probe is a vital technology for observing and exploring the universe. It is thus intensifying as an aerospace research focus on an international scale. Despite improving the frequency band, the conventional microwave communication technique has difficulty satisfying the increased demand for the enormous volume of scientific data returning to the Earth. With a carrier frequency that is several orders of magnitude higher than the microwave, free-space optical communication is a robust and promising method for achieving both high bit rates and long distances in deep space communication. In this article, the history of this technology is summarized and the objective laws are formulated, while key techniques and development trends are analyzed. Finally, useful concepts and suggestions are proposed for the development of deep space laser communication in China.
Journal Article
Orbital angular momentum and beyond in free-space optical communications
Orbital angular momentum (OAM), which describes tailoring the spatial physical dimension of light waves into a helical phase structure, has given rise to many applications in optical manipulation, microscopy, imaging, metrology, sensing, quantum science, and optical communications. Light beams carrying OAM feature two distinct characteristics, i.e., inherent orthogonality and unbounded states in principle, which are suitable for capacity scaling of optical communications. In this paper, we give an overview of OAM and beyond in free-space optical communications. The fundamentals of OAM, concept of optical communications using OAM, OAM modulation (OAM modulation based on spatial light modulator, high-speed OAM modulation, spatial array modulation), OAM multiplexing (spectrally efficient, high capacity, long distance), OAM multicasting (adaptive multicasting,
-dimensional multicasting), OAM communications in turbulence (adaptive optics, digital signal processing, auto-alignment system), structured light communications beyond OAM (Bessel beams, Airy beams, vector beams), diverse and robust communications using OAM and beyond (multiple scenes, turbulence-resilient communications, intelligent communications) are comprehensively reviewed. The prospects and challenges of optical communications using OAM and beyond are also discussed at the end. In the future, there will be more opportunities in exploiting extensive advanced applications from OAM beams to more general structured light.
Journal Article
The shared world : perceptual common knowledge, demonstrative communication, and social space
\"The Shared World offers a new treatment of the capacity to perceive, act on, and know about the world together with others. It develops the view that creatures capable of joint attention stand in a unique perceptual and epistemic relation to their surroundings: they operate in an environment that they, through communication with their fellow perceivers, help constitute. This environment is characterized by a specific spatial order. Joint perceivers determine the location of the object of their attention and action relative to their respective standpoints, and thus operate with a spatial frame of reference in which these standpoints are presented as centres of perception and action. The resulting theory casts light on a range of philosophical and psychological issues: the essay discusses demonstrative reference in communication, common knowledge about jointly perceived objects, and spatial awareness in joint perception and -action. It integrates these social phenomena into a more general discussion about the nature of mind and argues for their crucial relevance in the context of that discussion\"-- Provided by publisher
Book
Private communication with quantum cascade laser photonic chaos
Mid-infrared free-space optical communication has a large potential for high speed communication due to its immunity to electromagnetic interference. However, data security against eavesdroppers is among the obstacles for private free-space communication. Here, we show that two uni-directionally coupled quantum cascade lasers operating in the chaotic regime and the synchronization between them allow for the extraction of the information that has been camouflaged in the chaotic emission. This building block represents a key tool to implement a high degree of privacy directly on the physical layer. We realize a proof-of-concept communication at a wavelength of 5.7 μm with a message encryption at a bit rate of 0.5 Mbit/s. Our demonstration of private free-space communication between a transmitter and receiver opens strategies for physical encryption and decryption of a digital message.
Free-space communication in the mid-IR domain has many potential applications, but security is still challenging. Here, the authors use chaos synchronization in a QCL-based free-space link as a way to increase privacy of such transmissions.
Journal Article
A beautiful friendship
Twelve-year-old Stephanie Harrington, a genetically-enhanced girl on the pioneer planet of Sphinx, bonds with a treecat, a telepathic and fully sentient animal, putting her in danger from highly placed enemies who want to ensure that the planet remains entirely in human hands.
Book
Simulating thick atmospheric turbulence in the lab with application to orbital angular momentum communication
We describe a procedure by which a long ( ) optical path through atmospheric turbulence can be experimentally simulated in a controlled fashion and scaled down to distances easily accessible in a laboratory setting. This procedure is then used to simulate a 1 km long free-space communication link in which information is encoded in orbital angular momentum spatial modes. We also demonstrate that standard adaptive optics methods can be used to mitigate many of the effects of thick atmospheric turbulence.
Journal Article
The knife of never letting go
Pursued by power-hungry Prentiss and mad minister Aaron, young Todd and Viola set out across New World searching for answers about his colony's true past and seeking a way to warn the ship bringing hopeful settlers from Old World.
Book
A novel free space communication system using nonlinear InGaAsP microsystem resonators for enabling power-control toward smart cities
Nowadays, the smart grid has demonstrated a great ability to make life easier and more comfortable given recent advances. This paper studies the above issue from the perspective of two important and very useful smart grid applications, i.e., the advanced metering infrastructure and demand response using the instrumentality of a set of well-known scheduling algorithms, e.g., best-channel quality indicator, log rule, round robin, and exponential–proportional fairness to validate the performance. To increase the data transmission bandwidth, a new concept of optical wireless communication known as free-space optical communication (FSO) system based on microring resonator (MRR) with the ability to deliver up to gigabit (line of sight) transmission per second is proposed for the two studied smart grid applications. The range between 374.7 and 374.79 THz frequency band was chosen for the generation of 10 successive-carriers with a free spectral range of 8.87 GHz. The ten multi-carriers were produced through drop port of the MRR. The results show up to 10 times bandwidth improvement over the radius as large as 600 m and maintain receive power higher than the minimum threshold (− 20 dBm) at the controller/users, so the overall system is still able to detect the FSO signal and extract the original data without detection.
Journal Article