Satellite Laser Communication Research Articles

Two-Frequency Mutual Coherence Function of a Gaussian Beam Pulse Propagated Through Non-Kolmogorov Turbulent Atmosphere

Over the past half century, satellite-laser-communication technology has been the focus in many countries and areas due to its higher data transmission rates, smaller terminals, low probability of intercept, etc. Much manpower and material and financial resources have been put into the development of this technology. Usually, longer pulses can be modeled as if they were continuous-wave pulses during the time when the pulse is transmitted. However, this is not the case for ultrashort pulses that are usually used as a carrier in satellite-laser communication. For satellite-to-ground or ground-to-satellite links, the atmospheric effects are more deleterious to the laser pulse and their analysis is also more complicated. For a long time, laser pulse propagation in the turbulent atmosphere were studied based on the Kolmogorov model. However, increasing experimental evidence and theoretical investigations have shown that the Kolmogorov model is not the only possible turbulent one in the atmosphere, and there exists another turbulence, namely, the non-Kolmogorov turbulence. So it is necessary to perform the analysis of the laser-pulse propagation in the non-Kolmogorov turbulence. The two-frequency mutual coherence function (MCF) plays an important pole in determining the basic characteristics associated with the laser-pulse propagating in the atmospheric turbulence. In this paper, we consider a theoretical power spectrum of the refractive-index fluctuations with a generalized power law, derive the two-frequency MCFs of a Gaussian-beam pulse in weak turbulence for a horizontal path, and analyze the influence of spectral power-law variations on the two-frequency MCFs. We present an analytical expression for a collimated-beam pulse.

The influence of space irradiated PIN photodetector on BER in satellite laser communication system

By analyzing the radiation dose on PIN photodetectors in space radiation environment, the variation of photocurrent and dark current after radiation is obtained. On the basis, the bit error rate of satellite laser communication based on space radiation dose of PIN photodetectors is established. According to simulation, when radiation dose is about 1.6×103Gy and 7×104Gy, bit error rate reaches 10−6 induced by 50MeV and 10MeV protons separately; and when radiation dose is within the range of 5×10Gy–6×105Gy, electrons and gamma-ray irradiation also cause increase in bit error rate to 10−6. The principle of damage dose on bit error rate is investigated, and the influence of decision threshold on bit error rate is further discussed. The result shows that when radiation dose is 1MGy, if decision threshold is increased from 4.3×10−7A to 5.5×10−7A, bit error rate will decrease about 4 orders of magnitude. Hence, a proper decision threshold can improve system bit error rate efficiently.

Wander of a Gaussian-Beam Wave Propagated Through a Non-Kolmogorov Turbulent Atmosphere

Both increasing experimental evidence and some results of theoretical investigation have shown that there exist two kinds of turbulence in the aerosphere, Kolmogorov and non-Kolmogorov turbulence. Thus, it is necessary to improve the theory of optical wave propagation through atmospheric turbulence, namely, study the laser-beam propagation in non-Kolmogorov turbulence, before analyzing the joint influence of the Kolmogorov turbulence and non-Kolmogorov one on satellite laser communication. The beam wander will lead to the performance degradation of satellite laser communication systems and exert an influence on the achievement and stability of its links. In this paper, we consider a theoretical power spectrum of refractive-index fluctuations with a generalized power law in order to derive the variance of Gaussian-beam wave wander in weak turbulence for a horizonal path and analyze the influence of spectral power-law variations on the beam wander. We show that the expression for the beam-wander variance is of concise closed form and independent of the optical wavelength.

Design and Analysis InGaAs Near-IR Nanowire Photodetector for High Speed Satellite Laser Communication Application

InGaAs is direct and narrow bandgap material with ultrahigh electron mobility, and is a promising candidate for optoelectronic device in the near-infrared region. The main objective of this manuscript is to design an InGaAs semiconductor-based photodetectors nanowire infrared photodetector, which would be manipulated in optical response wavelength range at room temperature with high-detective and fast-responsive performances. Considering into account mature technology in laser device and for maximizing 1.55 um optical communication performance, the design of achieved bandwidth is >1 Gbps. According to the theoretical calculations, the fundamental parameters of the InGaAs core-shell nanowire APD photodetector device are obtained, with certain values of single nanowire diameter, lateral size and applied voltage,r=100 nm,l=1 μm,Vbias=10 V. Meanwhile, we deal with the electrons mobility of the internal nanowire based on three factors, size effect, temperature and electric field effect. The results demonstrate that the InGaAs nanowire APD is potential candidatefor high rate in satellite laser communication field.

基于合作信标的卫星激光通信瞄准捕获仿真系统

基于合作信标的卫星激光通信瞄准捕获仿真系统

空间辐射下卫星光通信系统半导体激光器的可靠性估计

空间辐射下卫星光通信系统半导体激光器的可靠性估计

BER performance of MSK in ground-to-satellite uplink optical communication under the influence of atmospheric turbulence and detector noise

Minimum shift keying (MSK) has been widely used in fiber optical communication and free-space optical communication. In order to introduce MSK into satellite laser communication, the bit-error rate (BER) performance of the MSK scheme is investigated in uplink communications under the influence of atmospheric turbulence consisting of weak fluctuation and beam wander. Numerical results indicate that the BER performance of MSK is much better than the performance of on-off keying (OOK). With the laser power being 4W, the improvement is 5dB in coherent demodulation and 15dB in delay coherent demodulation. Furthermore, compared with OOK, optimal values of the divergence angle, receiver diameter, and transmitter beam radius are easier and more practical to achieve in the MSK scheme. The work can benefit ground-to-satellite laser uplink communication system design.

Investigation of the Performance of OOK, 2DPSK, QDPSK in Downlink of Ground-to-Satellite Laser Communication Systems

With the development of satellite laser communication, modulation scheme has been the key technique for the modulation subsystem. The performance in terms of bite-error rate of OOK, 2DPSK, QDPSK used in the downlink of the ground-to-satellite laser communication systems are compared with the consideration of the combined effects of both intensity scintillation and detector noise. Simulation results are given and the advantages and disadvantages of the three modulation schemes are also studied. The design of the downlink of ground-to-satellite laser communication system can benefit from this work.

Uplink laser satellite-communication system performance for a Gaussian beam propagating through three-layer altitude spectrum of weak-turbulence

Uplink laser satellite-communication (satcom) system performance has been extensively studied under the assumption that atmospheric turbulence statistics obey a Kolmogorov power-law spectrum model. Unfortunately recent evidence has indicated that Kolmogorov spectrum is sometimes incomplete to describe atmospheric turbulence statistics properly, in particular in the upper atmosphere. In this paper, we use a three-layer attitude spectrum model that exhibits non-Kolmogorov properties in portions of the troposphere and stratosphere. Using this spectrum in weak turbulence, we analyze the bit-error rate (BER) performance of an uplink laser satcom system with a collimated untracked Gaussian beam subject to scintillation and beam wander impairments. Our theoretical results show that the difference in BER between the three-layer altitude spectrum and the Kolmogorov spectrum is not appreciable for smaller transmitter beam radius, but is significant at larger transmitter beam radius. Furthermore, for a given laser wavelength or zenith angle, the optimum transmitter beam radius that can minimize the BER is very different between the two turbulence spectrums.

Effect of non-Kolmogorov turbulence on beam spreading in satellite laser communication

In the past half a century, satellite laser communication has caught the attention of scientists due to its distinct advantages in comparison with conventional satellite microwave communication. For ground-to-satellite and satellite-to-ground data links, the atmosphere is a part of the communication channel; thus, atmospheric turbulence severely degrades the performance of satellite laser communication systems. In general, the Kolmogorov turbulence model is used to study the effect of atmosphere turbulence on satellite laser communications since it has been confirmed by numerous direct measurements of temperature and humidity fluctuations in the atmospheric boundary layer. However, increasing experimental evidence and theoretical investigations have shown that the Kolmogorov theory is sometimes inadequate to describe atmospheric statistics properly, in particular, in some domains of the atmosphere. We analyze the joint influence of Kolmogorov turbulence from the ground to 6 km and non-Kolmogorov turbulence above 6 km on the spot size associated with the uplink and downlink propagation channels for a satellite laser communication system in the geosynchronous orbit, using a power spectrum of non-Kolmogorov turbulence with power law −5 that describes the refractiveindex fluctuations in the atmosphere above 6 km and considering the combined power spectrum of Kolmogorov and non-Kolmogorov turbulence. Before this analysis, we study the joint influence of the Kolmogorov turbulence from the ground to 6 km and non-Kolmogorov turbulence above 6 km on the scintillation indices of laser beams.

Results of Kirari optical communication demonstration experiments with NICT optical ground station (KODEN) aiming for future classical and quantum communications in space

Bi-directional ground-to-satellite laser communication experiments were successfully performed between the optical ground station developed by the National Institute of Information and Communications Technology (NICT), located in Koganei City in suburban Tokyo, and a low earth orbit (LEO) satellite, the “Kirari” Optical Inter-orbit Communications Engineering Test Satellite (OICETS). The experiments were conducted in cooperation with the Japan Aerospace Exploration Agency (JAXA), and called the Kirari Optical communication Demonstration Experiments with the NICT optical ground station (or KODEN). The ground-to-OICETS laser communication experiment was the first in-orbit demonstration involving the LEO satellite. The laser communication experiment was conducted since March 2006. The polarization characteristics of an artificial laser source in space, such as Stokes parameters, and the degree of polarization were measured through space-to-ground atmospheric transmission paths, which results contribute to the link estimation for quantum key distribution via space and provide the potential for enhancements in quantum cryptography on a global scale in the future. The Phase-5 experiment, international laser communications experiments were also successfully conducted with four optical ground stations located in the United States, Spain, Germany, and Japan from April 2009 to September 2009. The purpose of the Phase-5 experiment was to establish OICETS-to-ground laser communication links from the different optical ground stations and the statistical analyses such as the normalized power, scintillation index, probability density function, auto-covariance function, and power spectral density were performed. Thus the applicability of the satellite laser communications was demonstrated, aiming not only for geostationary earth orbit-LEO links but also for ground-to-LEO optical links. This paper presents the results of the KODEN experiments and mainly introduces the common analyses among the different optical ground stations.

Influence of non-kolmogorov turbulence on intensity fluctuations in laser satellite communication

Satellite laser communication holds the potential for high-bandwidth communication, but the atmosphere can significantly affect the capability of this type of communication systems for satellite-toground and ground-to-satellite data links to transfer information consistently and operate effectively. Usually the influence of atmosphere on satellite laser communication is investigated based on the Kolmogorov turbulence model. However, both increasing experimental evidence and theoretical investigations have shown that the Kolmogorov theory is sometimes incomplete to describe the atmospheric statistics properly, in particular, in some portions of the atmosphere. Considering a non-Kolmogorov turbulent power spectrum with power law −5 that describes the refractive-index fluctuations in the atmosphere above 6 km, we calculate the scintillation index of a lowest-order Gaussian-beam wave under the weak-fluctuation condition. Then, considering a combined power spectrum of refractiveindex fluctuations and using the expression obtained, we analyze the joint influence of the Kolmogorov turbulence from the ground to 6 km and non-Kolmogorov turbulence above 6 km on the scintillation indices of laser beams used in ground-to-satellite and satellite-to-ground laser communication links. We show that the scintillation index in satellite laser communication is equal to the sum of the scintillation indices induced by the Kolmogorov turbulence from ground to 6 km and that caused by the non-Kolmogorov turbulence above 6 km. Also we investigate variations of the scintillation index with the beam radius on the transmitter, wavelength, the radial distance, and zenith angle. Finally, comparing the scintillation index induced by these two turbulences with the conventional results, we show that the scintillation index induced by these two turbulences is a bit smaller than the conventional results.

卫星激光通信滤光膜的研制

In order to satisfy the special requirements of super velocity data transmission in satellite laser communication,a type of multi-band filter membrane with high reflection at 532 nm,632 nm,1 064 nm wavelengths and high transmission at 808 nm,1 550 nm wavelengths is prepared,adopting electronic beaming vacuum depositing method with the aid of ion assistant deposition technology.By selecting H4 and SiO2 as the high and low refractive index materials,continually optimizing the film system design curve,reducing the number of sensitive layers,the film structure is obtained that is easily prepared.The thin films are prepared through electron beam heating evaporation and ion assisted deposition system,and the film thickness is controlled using crystal-controlled and light control monitoring methods at the same time.By continually adjusting the process,the film laser damage resistance ability is improved,the control error is reduced,the transmittance of the transmission band and the reflectance of the reflection band are increased,and the filter membrane with better spectral performance is obtained.The experimental results show that the filter membrane can withstand rain,salt spray,high and low temperature and other environments,and meet the requirements in satellite laser communication.

Performance Improvement of the Tracking System of a Satellite Laser Communication

Free Space Optics (FSO) is an optical communication technology that uses light propagating in free space to transmit data between two points. The technology is useful where the physical connections by the means of optical fibre cables are impractical to use due to high costs or other considerations. FSO has been proposed by using a laser. FSO is considered as one of the most popular choices for inter-satellite communication where the performance is limited by “satellite vibration”. FSO cannot achieve a stable and ‘healthy’ link due to such type of vibration. The ultimate disadvantages include misalignment in tracking, signal attenuation and high BER (bit error rate). Hence the satellite vibrations need to be compensated (or minimized). This paper introduces the feed-forward vibration compensation model by introducing PID controller. The simulation results indicate that the proposed method minimizes the vibration effects and hence reduces BER in satellite laser communication system [7]. General Terms Satellite, Vibration effect, PID controller, Feed-forward compensator.

Analysis of complex axis control loop in satellite laser communications

Satellite laser communication involves communications between GEO satellites and LEO satellites. The optical link can be built by the accurate pointing and tracking, which often employs the combination effect of coarse pointing assembly and fine pointing assembly. In order to achieve this goal with double rotated wedged-plate lenses and fast steering mirror that perform the scanning function of the coarse pointing assembly and the fine pointing assembly, mathematic model of transfer function of control loop is obtained by analyzing the total control loop for such complex axis. One can also get the optimized programs between coarse and fine pointing assembly.

Decentralized Robust Adaptive Control for Attitude Synchronization Under Directed Communication Topology

T HE need to maintain accurate relative orientation between spacecraft is critical in many satellite formation missions. For instance, in interferometry application, the relative orientation between spacecraft in a formation is required to be maintained precisely during formation maneuvers. In interspacecraft laser communication operation, the participating spacecraft are also required to maintain accurate relative attitude throughout the communication process. This control problem, commonly referred to as attitude synchronization in the literature, has attracted much research attention. Various solutions have been proposed and these can be broadly classified according to the advocated techniques: leader– follower [1–4], virtual structure [5,6], behavior-based [7–11], and graph-theoretical approach [12–15]. In particular, the graph-theoretical approach has been actively studied for cooperative control of multi-agent system using limited local interaction [16,17] and was adopted for attitude synchronization problem in [12–15]. In the above-cited decentralized attitude synchronization results, except [14,15], it is assumed that the interspacecraft communication links are undirected (i.e. bidirectional). However, in practice, the interspacecraft communication topology may be restricted to be directed, such as in unidirectional satellite laser communication system. The control problem of attitude synchronization under directed communication topology is more challenging as compared with the case with undirected communication topology. This issue was studied in [14] but the proposed control law requires derivative of the angular velocity, which may introduce additional noise into the system. Furthermore, the attitude-tracking performance analysis in [14] is applicable only to the casewhere the directed graph can be simplified to a graph with only one node. This constraint on communication topology is relaxed in [15], which uses modified Rodriguez parameters and Euler– Lagrange system to describe the satellite attitude dynamics. However,modifiedRodriguez parameters contain singularity and are thus not suitable for the development of globally stabilizing control algorithms. This Note proposes a decentralized adaptive sliding-mode control lawwhich regulates attitude and angular velocity errors of individual spacecraft with respect to reference commands and minimizes relative attitude and angular velocity errors between spacecraft. Thus, the proposed control law ensures that each spacecraft attains desired time-varying attitude and angular velocity while maintaining attitude synchronization with other spacecraft in the formation even in the presence of model uncertainties and external disturbances. Moreover, the design is applicable to general communication topology and is not restricted to ring topology or undirected communication topology. In the following section, unit quaternion representation will be introduced into the satellite attitude control problem and algebraic graph theory will be applied to describe general directed communication topology.

卫星激光通信现状与发展趋势

卫星激光通信现状与发展趋势

Optimization of Satellite Laser Communication Subject to Log-Square-Hoyt Fading

In the existing studies of satellite laser communications, the variances in the azimuth and elevation axes of a swaying transmitter are usually assumed to be identical. In this correspondence, the analysis is extended to the general case in which these two variances are not the same. It is shown that the transmitter radial pointing error angle follows the Hoyt distribution. Furthermore, we prove that the instantaneous signal-to-noise ratio (SNR) follows the log-square-Hoyt distribution. Based on these results, we establish an optimization model to minimize the outage probability, subject to a specified transmitter power, by adjusting some system parameters such as the transmitter gain. A closed form of the solution is obtained and a set of representative curves are presented.

In-orbit measurements of spacecraft microvibrations for satellite laser communication links

Angular microvibrations of platform jitter on the optical inter-orbit communications engineering test satellite are measured in space during ground-to-satellite laser communication links. The microaccelerations are measured by the onboard accelerometers at a sampling rate of 2048 Hz. The angular microvibrations are estimated from the measured microaccelerations using the tracking characteristics of the laser communications terminal and the conversion factor on the basis of microvibration data obtained from ground-based tests. The power spectral density (PSD) of the satellite microvibrations is analyzed by using the fast Fourier transform analysis and the data length is examined according to the frequency resolution of the PSD. The in-orbit measurements of the PSDs are compared with those obtained from the ground test. The angular microvibrational base motion is estimated and a PSD up to 1024 Hz is additionally provided as a database of the real measurement results with previously obtained in-orbit measurements. The measured results will contribute to the angular jitter estimation and the design of a tracking control loop for space laser communication systems in the future.

卫星激光通信复合轴光跟瞄技术及发展

卫星激光通信复合轴光跟瞄技术及发展