Satellite Laser Communication Research Articles

Concept and Feasibility Analysis of the Alba Cubesat Mission

AbstractAlbaSat is a 2-Unit CubeSat which is being developed by a student team at the University of Padova. The Alba project aims to design, build, test, launch, and operate the first student CubeSat of the University of Padova, featuring four different payloads. The first goal is to collect data regarding the debris environment in Low Earth Orbit, the second goal is the study of the satellite vibrations, the third one is about CubeSat attitude determination through laser ranging technology, and the fourth goal concerns satellite laser and quantum communication. The Alba CubeSat mission has been selected by the European Space Agency to join the Fly Your Satellite! Design Booster program in December 2022. This paper presents the feasibility study of the Alba CubeSat mission reproduced in the framework of the “Space Systems Laboratory” class of Master of Science in Aerospace Engineering at the University of Padova. In the beginning, a mission requirements definition was conducted. After that, the mission feasibility was considered, with preliminary requirements verification to assess the ability of the spacecraft to survive the space environment, including compliance with Debris Mitigation Guidelines, ground station visibility and minimum operative lifetime evaluation. The Alba mission sets a base for a better understanding of the space environment and its interaction with nanosatellites, and an improvement of the accuracy of debris models. Furthermore, this paper, describing the educational experience and the results achieved, will provide a useful example for future students’ studies on CubeSat mission design.

All-optical suppression on the impact of Sun outage in laser satellite communication systems by using a nonlinear semiconductor optical amplifier

All-optical suppression on the impact of Sun outage in laser satellite communication systems by using a nonlinear semiconductor optical amplifier

Broadband free space 2 × 4 90° optical hybrid for satellite laser communication.

We design a broadband free space 2×4 90° optical hybrid over a spectral window of 1000-1200nm and 1470-1650nm and verify the feasibility of the scheme experimentally. The hybrid consists of three broadband polarization beam splitters, an achromatic λ/4 wave plate, and three achromatic λ/2 wave plates. The fabricated hybrid exhibits a good quadrature phase response with an interchannel imbalance of 0.93-1.07 and a low phase deviation of less than 0.2° under the typical communication wavelengths of 1064nm and C-band. The experimental results of the heterodyne method show that the proposed hybrid can effectively solve the wavelength incompatibility problem in satellite laser communication and realize interconnection at different wavelengths. The designed hybrid (without coupling) has a measured insertion loss of no more than 7.34dB at 1064nm and C-band. A high-speed transmission experiment with BPSK format has been conducted to verify the performance of the assembled device.

Simulation Study on Self-Focusing Effect of Satellite Laser Communication Under Extreme Ionospheric Conditions

Simulation Study on Self-Focusing Effect of Satellite Laser Communication Under Extreme Ionospheric Conditions

Current Status and Development Trend of Satellite Laser Communication

Current Status and Development Trend of Satellite Laser Communication

Analysis of Coaxiality Error Induced by the Cube Corner Retro-Reflector Geometrical and Assembly Errors of an Acquisition, Pointing, and Tracking System

Satellite laser communication is a promising technology for the next-generation communication system. Its communication performance is subject to the APT beam-pointing accuracy. One of the most important problems is reducing the coaxiality error before the APT starts working. However, the coaxiality error is difficult to correct effectively owing to the lack of empirical guidance based on qualitative analysis. We study the inducement that will generate coaxiality errors. The mathematical model of the influence of the CCR dihedral angle error and planeness error on the spot centroid measurement are built, and an analysis is performed. The model of the beam-pointing error induced by the APT element’s assembly error is built, and the pointing error change rule is explored. Furthermore, the coaxiality performance simulation is performed in the presence of a CCR geometrical error while considering the assembly error. The results show that the coaxiality error has a nonlinear characteristic. The CCR planeness error has a greater influence on coaxiality deviation than that of dihedral angle error under certain conditions. This research is relevant to the design and test work of the APT system.

Adaptive polar coding scheme using hybrid pilot and frozen bits for satellite laser communications

Adaptive polar coding scheme using hybrid pilot and frozen bits for satellite laser communications

Performance of HQAM/XQAM Laser Communication System in Anisotropic Non-Kolmogorov Ground–HAP–Satellite Uplink

Satellite laser communication can achieve high-speed, high-precision, and high-security broadband communication without being constrained by the electromagnetic spectrum, which has attracted attention. So, this paper proposes the use of a high-altitude platform (HAP) under anisotropic non-Kolmogorov turbulence to improve the communication performance of the system. Cross quadrature amplitude modulation (XQAM) and hexagon quadrature amplitude modulation (HQAM) are applied to the ground–HAP–satellite (G-H-S) laser communication system. Considering the combined effects of uplink light intensity scintillation, beam wander, and the angle of arrival fluctuation, the G-H-S system’s bit error rate (BER) closure expression is derived under the EW distribution. Simultaneously, the relationship between the G-H-S system’s signal-to-noise ratio (SNR) and BER under different anisotropic factor u values is simulated and compared with the traditional ground–satellite (G-S) system. The results show that the communication performance of the G-H-S system with HQAM modulation is better. In addition, the effects of the zenith angle, receiving aperture, transmitter beam radius, and beam divergence angle on the BER performance of the system are also studied. Finally, the correctness of the analysis results is verified via Monte Carlo simulation. This research will benefit the design and optimization of satellite laser communication systems.

Beam Scanning and Capture of Micro Laser Communication Terminal Based on MEMS Micromirrors.

With the development of space laser communication and the planned deployment of satellite Internet constellations, there is a growing demand for microminiature laser communication terminals. To meet the requirements of size, weight and power (SWaP), miniaturized terminals require smaller drive components to complete on-orbit scanning and capture, which must be fast and efficient to enable satellite laser communication networks. These miniaturized laser communication terminals are highly susceptible to the impact of the initial pointing accuracy of the laser beam and microvibrations of the satellite platform. Therefore, this paper proposes a laser scanning-capture model based on a Micro-electromechanical Systems (MEMS) micromirror that can provide a fast, large-scale scanning analysis. A scanning overlap factor is introduced to improve the capture probability under the influence of microvibrations. Finally, experimental analysis was carried out to verify the effectiveness of the proposed model, which can establish a theoretical basis for future ultra-long-distance microspace laser communication.

Deep-learning-based path computation without routing convergence in optical satellite networks

Low Earth orbit (LEO) satellite networks, which are composed of multiple inter-connected satellites, have become important infrastructure for future communications. Benefiting from the high bandwidth and anti-interference of satellite laser communication, optical satellite networks, in which satellite links are lasers, can provide global Internet services and have become a research trend. The orbit at a lower altitude has advantages such as low latency, low cost, and easy deployment in LEO optical satellite networks. Meanwhile, the movement of satellites is fast and thus will result in frequent changes for ground–satellite links. The conventional static routing strategy cannot perceive the network state; therefore, the static routing is inapplicable in the case of link failure or congestion. Dynamic routing can ensure the accuracy of the network connection by routing convergence. However, the routing table needs to be updated frequently because of the highly dynamic topology, resulting in the increase in signaling overhead. To compute routing paths accurately while reducing the update frequency of the routing table, this paper proposes a path computation model based on deep learning. By learning the mapping relation of previous services and the routing paths, the model can directly output the routing path according to the current service request. Using this method, the path computation tasks depend less on the frequently updated routing table. The simulation results show that the paths computed by the proposed method are almost the same as the paths computed by Dijkstra’s algorithm, the average accuracy rate is above 90%, and the highest accuracy rate can reach 98.8%. Compared with traditional path computation, the proposed method needs to collect a large amount of previous data for training, and the training time is about several hours.

Analysis of atmospheric turbulence and vibration impact on the performance of satellite–ground laser communication beam

AbstractWith satellite laser communication, advantages can be achieved in high communication rate, precise beam pointing, high confidentiality, and light‐small terminal. Satellite–ground (SG) laser links also play a crucial role as trunk links. However, the SG link is influenced by atmospheric turbulence and platform vibration, these two factors will cause unstable link tracking. This paper focuses on the viewpoint of beam energy transmission, using the low‐frequency harmonic phase compensating method to establish the random phase screen. On the basis of this model, the laser beam energy distribution and the spot mass positioning error are analyzed considering turbulence taking vibration which is not considered in previous studies. The simulation results show that the spot mass center (SMC) is impressionable in strong turbulence under platform vibration, but in a weak turbulent environment, SMC is insensitive to vibration when turbulence and vibration are at the same noise level.

On-orbit demonstration of inter-satellite free-space optical stable communication enabled by integrated optical amplification of HPA and LNA.

Satellite free-space optical (FSO) communication is very promising in improving the bandwidth and capacity of space information networks in the future. However, the inter-satellite transmission distance of over 1000km leads to unstable optical beam pointing, acquisition, and tracking and then generates optical power jitter by a large margin before detection-demodulation. Therefore, it is difficult to realize high-stability and long-time FSO communication between satellites due to the generated bit error rate (BER) by jitter. In this paper, we report an autonomously self-designed and high-integration laser communication payload (LCP) and on-orbit-demonstrated inter-satellite 145min, zero-BER FSO stable communication with a line rate of 2.8Gbps. Moreover, based on the inter-satellite laser communication link, a video phone was clearly implemented for more than 10min, and authentic user data transmitted 459,149 packets, achieving results of zero-packet loss. Summarily, this on-orbit experiment demonstrated an excellent performance of the LCP owing to the distinctive design of integrating a high-power amplifier and low-noise amplifier optical amplification function. Our space mission was successfully completed, and the on-orbit demonstration results may offer a significant reference for the field of satellite laser communication and space information networks.

Energy-efficient routing based on a genetic algorithm for satellite laser communication.

Low earth orbit satellite laser communication has become an important part of communications due to its large capacity and low latency. The lifetime of the satellite mainly depends on the recharge and discharge cycles of the battery. The low earth orbit satellites frequently recharge under sunlight and discharge in the shadow, which leads satellites to age quickly. This paper studies the energy-efficient routing problem for satellite laser communication and builds the satellite ageing model. Based on the model, we propose an energy-efficient routing scheme based on the genetic algorithm. Compared with shortest path routing, the proposed method improves the satellite lifetime by about 300%, and the performances of the network are only slightly degraded, the blocking ratio increases by only 1.2%, and the service delay increases by 1.3 ms.

Cooperative relay orbital satellite optical communication under turbulent channels: Performance analysis

Free-space optical (FSO) or laser satellite communication (SatCom) can be enhanced to mitigate turbulent channels by using relay communication, which provides main advantages including lower mass, lower consumption, better throughput, and lower cost. Furthermore, laser SatCom is inherently resistant to jamming, interception, and interference. This letter provides a theoretical and simulation analysis of downlink optical cooperative relay SatCom. The performance analysis for the proposed model is investigated using outage probability (OP) and bit error rate (BER) with intensity modulation direct detection (IM/DD) technique and decode and forwarding (DF) technology. The average aperture radius and operating wavelength are studied to illustrate the impact of the number of relays on the required aperture diameter. Closed forms for OP and BER are derived for the cooperative relay optical SatCom in order to express the results in the form of elementary functions, taking into account the impact of the ideal number of relays, significant design considerations, operating wavelengths, and zenith angles on the overall system performance. The collected findings demonstrate that our cooperative relays outperform both serial and direct link benchmarks for a variety of system characteristics.

Uplink serial relay laser satellite communication over turbulent channel: performance analysis

Optical space communication as a relay satellite system has been employed. The use of laser satellite communication (SatCom) can alleviate the issues that RF satellite communication encounters. In this study, channel turbulence, additional technologies, intensity modulation direct detection (IM/DD), decoding, and forwarding (DF) are used to evaluate the effectiveness of a proposed laser uplink satellite relay communication model in terms of outage probability (OP) and bit error rate (BER) indicators. This article looks at the necessary channel properties to analyze how operating wavelength affects system performance and compares our results with those of the optical direct link. The performance of the system is investigated by looking at the necessary system parameters, which show the superiority of the proposed system over the optical downlink SatCom, which can improve the required aperture radius up to 10% and the overall system performance up to 57%.

Research progress of reliability of MEMS fast steering mirror for satellite laser communication

Research progress of reliability of MEMS fast steering mirror for satellite laser communication

A New Composite Control Strategy of Space Laser Pointing Mechanism Based on Active Disturbance Rejection Controller

The satellite laser communication pointing system driven by a permanent magnet synchronous motor (PMSM) should have high-precision fixed-point pointing and tracking performance. However, the system motor parameter perturbation and friction disturbances affect the performance of the system. A composite control strategy for the space laser pointing mechanism based on an active disturbance rejection controller (ADRC) is proposed to solve these problems. In order to mitigate the adverse effects of current loop parameter perturbation and speed loop friction disturbance on control performance, the improved current controller and speed controller based on ADRC are designed. On these bases, an improved feedforward position controller is designed. The proposed control strategy can effectively suppress the parameter perturbation of the current loop and the friction disturbance of the speed loop, thus improving the position tracking accuracy of the pointing mechanism for the laser communication system. Experiments are carried out based on the laser pointing mechanism platform to demonstrate the correctness and effectiveness of the proposed strategy.

Silicon photonic receiver for satellite laser communication terminals.

We report the optical performance of a photonic receiver for laser communication applications. The receiver is composed of 14 × 12 grating coupler arrays. The received optical signal power will be combined electrically via germanium photodiodes. The photonic receiver is designed for 20-µm to 30-µm mode field diameter (MFD) input sources. To maximize the fill factor of the 200 µm × 200 µm light-receiving area, a design strategy has been proposed. (1) Grating couplers are customized for compactness. (2) Periods of grating couplers are designed to work as end-fire and back-fire grating couplers for the same incident angle of the input laser source. (3) Different widths of waveguides are routed to minimize cross talk. The photonic receiver is evaluated with a 10-µm MFD source. As a result of the evaluation, the receiving area considering the minimum efficiency of -10.5 dB is 95% of the designed area when illuminating 20-µm to 300-µm MFD laser sources.

Performance analysis of weather‐dependent satellite–terrestrial network with rate adaptation hybrid free‐space optical and radio frequency link

SummaryDue to the rapid development of satellite laser communication technology, free‐space optical (FSO) links present a promising alternative to traditional radio frequency (RF) links. In this paper, taking the influence of weather factors into consideration, we investigate the performance of the hybrid FSO/RF links where the feeder link operates in the FSO band and the user link operates in the hybrid FSO/RF band. Specifically, the FSO feeder link is modeled by the gamma–gamma distribution in the presence of beam wander and pointing error, and the detection method adopts either the intensity modulation with direct intensity (IM/DD) or heterodyne detection. The RF user link is assumed to follow the shadowed Rician model. In addition, in order to improve the transmission rate of the link under the time‐varying satellite–terrestrial channel, a rate adaptation scheme is proposed. The performance of the system under study is evaluated in terms of the outage probability, average bit error rate (BER), and average transmission rate. Our results provide some important insights, for example, (1) due to the constraints of the feeder link and weather factors, there is an upper limit on the outage performance and bit error rate of the hybrid link; (2) the adaptive transmission strategy can significantly improve the transmission rate of the link compared with traditional design.

Modulator-Free Variable Multi-Rate FSO Communication 1 km Outfield Demonstration Based on Chirp-Managed Laser

Due to the high energy efficiency per bit and high sensitivity, Return-to-zero differential-phase-shift-keying (RZ-DPSK) is perfectly suitable for free-space laser communications. However, the conventional generation method of RZ-DPSK optical signal requires two modulators, which is costly, bulky, and heavy, significantly hindering the application of RZ-DPSK in size, weight, and power (SWaP)-constrained satellite platforms. In this paper, we propose and experimentally demonstrate a modulator-free variable multi-rate RZ-DPSK free-space optical (FSO) communication system based on chirp-managed laser (CML). Based on the proposed scheme, an FSO outfield experiment over 1 km has been successfully undertaken, achieving receiving sensitivities of −48.9 dBm and −45.6 dBm at 2.5 Gbps and 5 Gbps, with bit error rate (BER) of 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> without forward error correction (FEC), respectively. The performance of the proposed system is also investigated by studying the eye diagrams under two different test conditions of back-to-back transmission and 1-km free space transmission. In addition to the small size, lightweight and low cost, the proposed scheme shows great potential for a variety of FSO communication applications ranging from Cube-Star to larger satellite laser communication platforms.