Atmospheric Communication Channel Research Articles

The legal regime of quantum communication lines in free space

The article discusses the features of regulating communication in free space as a key technology for quantum communication. An analysis of domestic and foreign experience in regulating this technology has been conducted, which has made it possible to highlight the advantages and disadvantages of its legal regime compared to other types of communication. It has been proved that communication via free space has advantages over wired communication since it does not require using other people’s land or establishing an easement as there is no need for a wire to create an atmospheric communication channel, while at the same time it is impossible to establish a security zone around atmospheric communication lines to protect wired communication lines from construction on them. It has been proved that communication in free space has advantages over radio frequency communication, as it does not require obtaining a permit/license for the use of radio frequencies. However, atmospheric communication lines do not have legal protection against technical interference. In order to improve the legal regime for quantum communication lines in free space, it has been proposed to eliminate terminological ambiguity in regulatory legal acts, define atmospheric optical communication as a special legal entity requiring equal protection with other communication channels, include atmospheric optical quantum communications in the security zone system for communication lines and structures, and establish administrative liability for interference with laser communications analogous to radio frequency interference.

A multi-mode free-space delay interferometer with no refractive compensation elements for phase-encoded QKD protocols

We demonstrate a compensation-free approach to the realization of multi-mode delay interferometers, mainly for use in phase-encoded quantum key distribution (QKD). High interference visibility of spatially multi-mode beams in unbalanced Michelson or Mach–Zehnder interferometers with a relatively wide range of delays is achieved by the appropriate choice of the transverse size of the beam. We provide a simple theoretical model that gives a direct connection between the visibility of interference, the delay and the beam parameters. The performed experimental study confirms our theoretical findings and demonstrates measured visibility of up to 0.95 for a delay of 2 ns. Our approach’s simplicity and robust performance make it a practical choice for the implementation of QKD systems, where a quantum signal is received over a multi-mode fiber. The important application of such a configuration is an intermodal QKD system, where the free-space atmospheric communication channel is coupled into a span of the multi-mode fiber, delivering the spatially distorted beam to the remote receiver with minimal coupling loss.

Optical Antenna with Controlled Radiation Pattern for Application in Atmospheric Communication Channels

Optical Antenna with Controlled Radiation Pattern for Application in Atmospheric Communication Channels

Optical Antenna with Controlled Radiation Pattern for Application in Atmospheric Communication Channels

A mathematical model of a new optical (1550 nm) antenna with an electrically controlled radiation pattern is presented. The working principle is considered, and the main parameters are calculated. As distinct from existing solutions, the antenna does not require convergence of beams at a distance of one half of wavelength. In the framework of the model, an electro-optical switch based on lithium niobate is calculated. Such antenna elements as a phase shifter and deflector are presented and calculated

Analysis of total signal decay and capacity of information data in wireless atmospheric communication links. Part 2

Introduction: Analysis of total signal decay is based on prognosis of the total path loss occurring in the atmospheric communication links, accounting for effects of gaseous structures attenuation and scattering, hydrometeors (rain, snow and clouds) absorption and attenuation, and turbulent structures fast fading on radio and optical signals passing atmospheric channels with fading. Purpose: To perform a novel methodology of definition and estimation of effects of decay, absorption, scattering, and fading of radio and optical signals propagating in atmospheric channels in various meteorological conditions. Results: Wasanalyzed the impact of gaseous structures, hydrometeors and turbulent structures in total path loss for link budget design and in degradation of data stream parameters, such as capacity, spectral efficiency and bit-error-rate, which lead in loss of information data signals passing such kinds of channels with fast fading and decrease of quality of service. An optimal algorithm was found of the total path loss prediction for various meteorological situations occurring in the real atmosphere at different heights and for various frequencies of radiated signals. A method was proposed of how to evaluate the data stream parameters, capacity, spectralefficiency and bit-error-rate, accounting for the effects of atmospheric turbulence impact on fast fading, which corrupts information passing such kinds of channels. All practical tests were illustrated by the use of the MATLAB utility. A new methodology was proposed on how to evaluate and estimate the capacity, the spectral efficiency, and the loss in energy and in the information data stream for different scenarios of radio and optical signals propagation via atmospheric channels with fading caused by different meteorological conditions. Practical relevance: The results obtained allow to achieve better accuracy of prognosis and increase quality of service in atmospheric communication channels.

Twisted rectangular Laguerre–Gaussian correlated sources in anisotropic turbulent atmosphere

The ability to impress twist phase on random sources has led to new insights into coherence theory as well as important applications in optical tweezers and optical communications. In the paper, a new class of twisted sources named rectangular Laguerre–Gaussian correlated (TRLGC) fields is introduced based on a superposition of a mutually incoherent, tilted and displaced partially coherent beams. The analytical expressions for the cross-spectral density and the second-order moments of a TRLGC beam propagating through anisotropic non-Kolmogorov turbulent atmosphere are derived. The evolution characteristics of a TRLGC beam such as the spectral intensity, the spectral degree of coherence, and the beam quality are investigated in detail. It is shown that higher values of twist factor can significantly suppress the anisotropic beam spreading induced by the anisotropy of turbulence. Moreover, owing to the twist phase and higher-order coherence parameter, the anti-turbulence capability of partially coherent beams is further enhanced. For anticipated atmospheric communication channel conditions, a comprehensive selection of initial beam parameters, receiver aperture size and receiver capability, etc., is very important. Our work is helpful for exploring new forms of twistable sources and enriches potential applications of novel partially coherent beams in free space optical communications.

Electromagnetic Wave Propagation in the Turbulent Atmosphere With an Anisotropic Exponent of the Spectrum

In this communication, we propose a new model for describing the anisotropy of turbulence relative to the vertical and horizontal directions, through the anisotropy of the structure function exponent. Using the obtained anisotropy spectrum, we calculate various parameters such as log-amplitude variance for various atmospheric communication channels with comparison to the classical Kolmogorov model and newer models developed in previous works.

Simulation of information transfer through atmospheric channels of scattered laser radiation propagation

Results of simulations of the pulse response of an atmospheric optical communication channel on scattered radiation at wavelengths of 0.3, 0.5, and 0.9 μm are considered. The performed analysis shows that the maximum power of the received information signal at base distances of 2–3 km and less between the source and receiving system is reached at λ = 0.3 μm; for longer base distances and low turbidity of the atmosphere, λ = 0.5 μm. The highest maximum power is observed at λ = 0.5 μm under high turbidity of the atmosphere and base distances of 3–10 km. However, if the base distances are longer than 10 km, the maximum of the information signal power is reached at λ = 0.9 μm. For an example of a laser source and receiving system, using calculation results for the pulse reaction of the atmospheric communication channel at λ = 0.5 μm, we estimate the limiting base distance between the source and receiver, as well as the limiting pulse frequency which is not filtered by the communication channel.

Atmospheric bistatic communication channels with scattering. Part 1. Methods of study

The paper considers the methods for theoretical and experimental study of bistatic optical communication schemes. A laboratory model of an optoelectronic communication system has been developed for experimental studies. Copper-vapor laser radiation at a wavelength of 510 nm was used as a source of signals. Test demonstration experiments were performed in the real atmosphere through atmospheric channels with a reflecting surface and a dense nonstationary aerosol-molecular structure. For theoretical studies, software means were developed for numerical statistical estimation of the energy and transfer characteristics of the bistatic atmospheric communication channels by the Monte Carlo method.

The effects of tilt corrected residual aberration on the detection probability of single-photon propagation in a slant path turbulent atmosphere

Based on the assumption of a pulse laser beam with an initial Gaussian temporal shape and a collimated fundamental-model Gaussian beam, the Rytov approximation and Kolmogorov spectrum model for the index-of-refraction fluctuation of atmosphere, the effect of turbulence on the probability density, acquisition transmittance probability, transmittance probability density, acquisition probability of single-photon propagation in atmospheric communication channel with z-tilt and centroid-tilt aberration corrected are studied theoretically. The probability density, acquisition transmittance probability, transmittance probability density and acquisition probability models for single-photon propagation in uplink path and downlink path are derived. Our results shown that the detection probability and the acquisition transmittance probability of the single-photon are obvious increase, when the beams are propagation in the z-tilt corrected communication channel.

The probability of orbital angular momentum states of single photons with Z-tilt corrected residual aberration in a slant path turbulent atmosphere

With Rytov approximation and Kolmogorov spectrum model of index-of-refraction fluctuation, we study the effects of turbulence aberration on the orbital angular momentum of single photons in atmospheric communication channel. A theoretical model of measurement probabilities of orbital angular momentum states for single photons propagation under the Zernike tilt corrected slant path turbulent atmosphere channel is established. Our research shows that tilt-corrected residual aberration not only damage the initial OAM, but also induce new OAM. With the increasing of D/ ρ 0, the number of the initial OAM photons will go down while the effective number of new OAM ascends. Meanwhile, the receiving probability of initial OAM photons declines, as the turbulence shifts from weak to strong. For Zernike tilt-corrected residual aberration, the receiving probability of initial OAM photons declines as the diameter of detector increases. The effect of Zernike tilt-corrected residual aberration on OAM of the photons is more larger than the effect of Zernike tilt turbulent aberration.