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Optical wireless video transmission technology combines the advantages of high data rates, enhanced security, large bandwidth capacity, and strong anti-interference capabilities inherent in optical communication, establishing it as a pivotal technology in contemporary data transmission networks. However, video data comprises a large volume of image information, resulting in substantial data flow with significant redundant bits. To address this, we propose an adaptive block sampling compressive sensing algorithm that overcomes the limitations of sampling inflexibility in traditional compressive sensing, which often leads to either redundant or insufficient local sampling. This method significantly reduces the presence of redundant bits in video images. First, the sampling mechanism of the block-based compressive sensing algorithm was optimized. Subsequently, a wireless optical video transmission experimental system was developed using a Field-Programmable Gate Array chip. Finally, experiments were conducted to evaluate the transmission of video optical signals. The results demonstrate that the proposed algorithm improves the peak signal-to-noise ratio by over 3 dB compared to other algorithms, with an enhancement exceeding 1.5 dB even in field tests, thereby significantly optimizing video transmission quality. This research contributes essential technical insights for the enhancement of wireless optical video transmission performance. [ABSTRACT FROM AUTHOR]

Optical wireless video transmission technology combines the advantages of high data rates, enhanced security, large bandwidth capacity, and strong anti-interference capabilities inherent in optical communication, establishing it as a pivotal technology in contemporary data transmission networks. However, video data comprises a large volume of image information, resulting in substantial data flow with significant redundant bits. To address this, we propose an adaptive block sampling compressive sensing algorithm that overcomes the limitations of sampling inflexibility in traditional compressive sensing, which often leads to either redundant or insufficient local sampling. This method significantly reduces the presence of redundant bits in video images. First, the sampling mechanism of the block-based compressive sensing algorithm was optimized. Subsequently, a wireless optical video transmission experimental system was developed using a Field-Programmable Gate Array chip. Finally, experiments were conducted to evaluate the transmission of video optical signals. The results demonstrate that the proposed algorithm improves the peak signal-to-noise ratio by over 3 dB compared to other algorithms, with an enhancement exceeding 1.5 dB even in field tests, thereby significantly optimizing video transmission quality. This research contributes essential technical insights for the enhancement of wireless optical video transmission performance.

The technology of coherent tracking based on signal beam nutation is presented in the paper. The working principle and advantage of the technology are analyzed. We provided the optical axis error detection algorithm and the selection method of nutation parameter. A simulation model of coherent tracking system was built, and the simulation results show that when half of the nutation angle is between 0.463 and 2 µrad, the degradation of the receiving sensitivity is less than 1 dB and the noise equivalent angle (NEA) is less than 0.02 μrad. When the nutation frequency is better than 10 kHz, the coherent tracking system can compensate vibration influence of some common satellite platform. The technology provides a new thought for free-space optical communication system design. [ABSTRACT FROM AUTHOR]

In dual-wavelength free-space optical communication systems, the wavefront distortion differences caused by the wavelength difference of the signal and beacon lights cannot be completely corrected. In this study, according to the method of geometric optics, the relationship between the wavefront phases of the signal and beacon lights is analyzed by establishing a mathematical model of the cross-correlation ratio of the arrival-angle fluctuation and phase relationship of different Gaussian-beam wavelengths under weak turbulence near the surface. The numerical results show that after Gaussian beams of different wavelengths propagate through the same atmospheric channel, the cross-correlation number of the arrival-angle fluctuation decreases with an increase in the wavelength difference, waist radius, and turbulence intensity, and increases with an increase in propagation distance. The beam-wavefront phase difference increases with an increasing wavelength difference. Finally, a wavefront distortion correction experiment of a dual-wavelength adaptive optical system verified the correctness of the wavefront phase-difference relationship between the signal light and beacon light established in this study. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of Nanjing University of Aeronautics & Astronautics is the property of Editorial Department of Journal of Nanjing University of Aeronautics & Astronautics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the laser inter-satellite communication link to realize information transmission between diff erent satellite nodes in satellite constellation, it can solve the problems of slow data rate and limited frequency resources in traditional satellite communication technology.Firstly, the main components of space laser communication technology and the research status at home and abroad were introduced.Then, the technical difficulties and main solutions of high-performance tracking, fast acquisition and high-throughput communication of the terminal were described respectively.Finally, the development trend of space laser communication miniaturization, lightweight and low power consumption technology were described, and the new technology was discussed, which provided relevant reference for the development of space laser communication technology.

In the Pulse Position Modulation (PPM) space optical communication channel estimation based on photon detection, two schemes for the estimation of signal photon average and background photon average are proposed. Scheme 1 is based on the characteristic of M order PPM, where only one of the M soots has a sggnal optical slot. The sggnal photon average and the back-ground photon average are roughly estimated by comparing the number of photons rn each soot rn each symbol counted by the photon detector and by counting the total number of photons in each soot in the error correction frame. The proposed method rn scheme 2 js based on that n scheme 1. The sggnal optical soot poston js re-determined by dedsion feedback n the Serially Con-catenated Pulse Poston Modu!ation (SCPPM) system. Since the exsstence of SCPPM accumulator leads to error propagation, the soft information output by decoding ss irst nntereeaved, and then mapped from btt to PPM symbol after hard deiion and accumu!ation. Frnally, the poston of sggnal optical soot is re-determined to obtarn more accurate sggnal photon average and background photon average. [ABSTRACT FROM AUTHOR]

Deep-space free-space optical (FSO) communication utilized the light wave as carriers for information transfer which has the major benefit of small size, lightweight, and low consumption compared with microwave communication loaded with the same data rate. The M-ary pulse-position modulation (M-PPM) format is a favorable choice for deep-space FSO communication by means of its high sensitivity. The preamplified thresholded M-PPM technique has been confirmed, and a corresponding demonstration has been accomplished with data rates of 1.25 Gbps and 2.00 Gbps separately. The receiving sensitivities (BER@1 × 10−3) of 1.25 Gbps and 2.00 Gbps 16-PPM have been detected as -57.51 dBm (11.04 photons/bit) and -55.03 dBm (12.25 photons/bit), respectively. Simultaneously, the high extinction ratio of M-PPM has been achieved, for example, the extinction ratio of 16-PPM has been detected as 39.51 and 38.27 dB for 1.25 Gbps and 2.00 Gbps, which are 17.60 and 17.44 dB higher than that of on–off keying (OOK) modulation, respectively. The results imply that our communication scheme possessed high sensitivity and eliminated the requirements of single-photon detectors (SPDs) and high-speed analog-to-digital converters (ADCs) which finds an alternative solution for deep-space FSO communication.

In the Pulse Position Modulation (PPM) space optical communication channel estimation based on photon detection, two schemes for the estimation of signal photon average and background photon average are proposed. Scheme 1 is based on the characteristic of M-order PPM, where only one of the M slots has a signal optical slot. The signal photon average and the background photon average are roughly estimated by comparing the number of photons in each slot in each symbol counted by the photon detector and by counting the total number of photons in each slot in the error correction frame. The proposed method in scheme 2 is based on that in scheme 1. The signal optical slot position is re-determined by decision feedback in the Serially Concatenated Pulse Position Modulation (SCPPM) system. Since the existence of SCPPM accumulator leads to error propagation, the soft information output by decoding is first interleaved, and then mapped from bit to PPM symbols after hard decision and accumulation. Finally, the position of signal optical slot is re-determined to obtain more accurate signal photon average and background photon average.

The performance of fi ber-based FSO with multiple apertures receiver system was studied for pulse position modulation (PPM) .Expressions of PPM modulated signal-to-noise ratio (SNR) and bit-error rate (BER) for fi ber-based FSO multiple apertures receiver system were presented based on the probability density function of Gamma-Gamma intencity distribution and non–central chisquare fi ber coupling effi ciency distribution under atmospheric infl uence.Selection combining (SC), equal gain combining (EGC) and maximum ratio combining (MRC) were considered to be three signal combining methods for multiple apertures receiver system.The BER performance of 4PPM modulted SC, EGC and MRC fi ber-based multiple apertures receiver system and single aperture receiver system with the same total aperture area were comparative analyzed by Monte Carlo simulation.The BER performance of fi ber-based multiple apertures receiver systems in 4PPM and 8PPM modulation modes were directly compared for diff erent combining methods.

In dual-wavelength free-space optical communication systems, the wavefront distortion differences caused by the wavelength difference of the signal and beacon lights cannot be completely corrected. In this study, according to the method of geometric optics, the relationship between the wavefront phases of the signal and beacon lights is analyzed by establishing a mathematical model of the cross-correlation ratio of the arrival-angle fluctuation and phase relationship of different Gaussian-beam wavelengths under weak turbulence near the surface. The numerical results show that after Gaussian beams of different wavelengths propagate through the same atmospheric channel, the cross-correlation number of the arrival-angle fluctuation decreases with an increase in the wavelength difference, waist radius, and turbulence intensity, and increases with an increase in propagation distance. The beam-wavefront phase difference increases with an increasing wavelength difference. Finally, a wavefront distortion correction experiment of a dual-wavelength adaptive optical system verified the correctness of the wavefront phase-difference relationship between the signal light and beacon light established in this study.

Copyright of Space-Integrated-Ground Information Networks is the property of Beijing Xintong Media Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A review of photonic integrated optical phased array (OPA) for space optical communication is presented. We review and summarize the typical works of the photonic integrated OPAs with one-dimensional and two-dimensional optical antenna array in recent years. The basic components of the photonic integrated OPA are introduced separately, including optical coupler, optical power division network, phase shifter, and optical antenna. In addition, the configuration of the optical antenna array and the control circuit are introduced for OPA beam steering. The basic principle and experiment setup for testing the radiation properties of the OPA are presented. A proof-of-concept nonuniform silicon integrated OPA with 64 antennas is designed and a one-dimensional beam steering range of 28° is achieved with beam width of about 0.25°. The challenges and development trends of large-scale integrated OPA chip applied in space optical communication are also discussed.

The Costas loop is an important technology for synchronous demodulation in space coherent communication. However, due to the limitation of the loop device and processing technology, it is difficult to achieve high-precision locking, which results in the Costas loop phase deviation and further affects the quality of the demodulation signal. In this paper, a closed-form bit error rate (BER) model is derived to evaluate the Costas loop phase deviation effect on BER performance in the space differential phase shift keying (DPSK) modulation and heterodyne detection communication system, considering laser phase noise, atmospheric turbulence, and detector noise. Based on the BER model, analytical solution simulation is conducted. The results show that the BER performance deteriorates varying with the increase of the Costas loop phase deviation. In addition, we research how to better balance the laser linewidth and Costas loop accuracy in the system design to ensure good communication status. We find that the wider the laser linewidth, the more stringent the Costas loop accuracy. Furthermore, the BER performance versus the Costas loop phase deviation under different satellite-to-ground communication system parameter settings including divergence angle, receiving aperture, signal laser power, and data rate are analyzed. This work provides valuable references for space optical coherent communication systems design. [ABSTRACT FROM AUTHOR]

Taking the deep space laser communication as the application background, based on multi-pulse position modulation and differential pulse position modulation, a new differential multi-pulse position modulation (DMPPM) mode is proposed. The DMPPM theory model is set up, and a comparative study and analysis of four modulation schemes of PPM, DPPM, MPPM and DMPPM has been developed. The simulation results show that the repetition rate of the pulse laser has a great influence on the four modulation modes. DMPPM has the characteristics of the smallest average symbol length, the largest average transmitting power, the maximum peak transmitting power, the maximum unit transmission rate, the smallest bandwidth demand and a higher transmission efficiency. The analysis shows that DMPPM is greatly influenced by the repetition frequency of the laser. It is very necessary to improve the repetition rate of the laser under the premise of ensuring the peak power of the pulse laser. DMPPM can become one of the excellent modulation schemes for deep space laser communication. [ABSTRACT FROM AUTHOR]

To evaluate the effect of crosstalk caused by wavelength deviation of reconstruction-equivalent-chirp (REC) integrated multi-wavelength laser arrays (MWLAs) on an optical free-space communication system in which wavelength division multiplexing (WDM) is applied, we derive the model of power penalty caused by the wavelength deviation of REC-MWLAs and the bit error rate (BER) of the system under atmospheric turbulence and conduct a numerical simulation. The two adjacent channels in arranged REC laser arrays are defined as the analysis scope. We find that the power penalty is more sensitive to the deviation of the channel itself than the adjacent channel as the frequency shift increases from 0 to 50 GHz. The numerical relationship between the BER and power penalty is drawn to further investigate the tolerance for wavelength deviation under the requirements of BER < 10 − 6 and BER < 10 − 9. In addition, for a smaller deviation of 5 GHz of the analyzed channel, the linewidth compression of the REC laser can decrease the power penalty from 1.3 to 0.7 dB, improving the system performance and moderating the demands for deviation of REC-MWLAs, and the gemination of channel spacing does not evidently reduce the requirement for deviation. The results of this work demonstrate the feasibility of REC-MWLAs as the light source of WDM free-space communication systems under atmospheric turbulence and provide an effective reference for the allowable deviation in the design and testing of MWLAs. [ABSTRACT FROM AUTHOR]

Abstract The coupling of space light to optical fiber is the key problem in free space optical communication. The diameter of fiber core is very small, which brings great difficulty to coupling. We first analyze the coupling model, and propose the conical fiber array as a new receiver to improve the efficiency. After that, the sample of conical fiber array is produced in the laboratory, and the testing experiment in micro vibration environment is carried out. In this experiment, two methods are used to measure the received optical power. In the first method, the light from nine fibers is merged into one with the optical splitter. In the second method, a large target avalanche photodiode (APD) is used to receive the light from nine fibers. Compared with our previous work, both measurement methods show the coupling efficiency of the conical fiber array is higher. Highlights • It is proposed to use the conical fiber array to receive the spatial light. • The mathematical coupling model of space light to the conical fiber array is set up. • The sample was produced and the experiment was done. • The experimental result shows the new receiver meets the desired receiving requirements. [ABSTRACT FROM AUTHOR]

Abstract: The coupling of space light to optical fiber is the key problem in free space optical communication. The diameter of fiber core is very small, which brings great difficulty to coupling. We first analyze the coupling model, and propose the conical fiber array as a new receiver to improve the efficiency. After that, the sample of conical fiber array is produced in the laboratory, and the testing experiment in micro vibration environment is carried out, in which two methods are used to measure the received optical power. In the first method, a large target avalanche photodiode (APD) is used to receive the light from nine fibers. In the second method, the light from nine fibers is merged into one with the optical splitter. Both measurement methods show the sample meet the desired receiving requirements. [ABSTRACT FROM AUTHOR]

In space optical communication system, the beam received by the Cassegrain receiving antenna needs to be coupled into the single-mode fiber before being detected. In this paper, a concave lens and a set of positive–negative angular cone lenses structure are designed to change the hollow beam generated by the Cassegrain receiving antenna into a solid beam. The coupling efficiencies for the hollow beam and solid beam are analyzed and numerically simulated. The simulation results show that the coupling efficiency can be improved and reaches the optimum value 0.808 after the hollow beam is changed into solid beam. Moreover, when the coupling lens and the fiber are not perfectly aligned, the coupling efficiency of the solid beam is larger than the hollow beam. The research results provide a way to improve the coupling efficiency of the Cassegrain receiving system and have practical application in the space optical communication system. • Analysis and numerical simulation for the coupling efficiency of the hollow beam. • Positive-negative angular cone lens to change the hollow beam into a solid beam. • Coupling efficiency is improved after the hollow beam is changed into a solid beam. [ABSTRACT FROM AUTHOR]