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Error performance of optical wireless communication systems exercising BPSK subcarrier intensity modulation in non-Kolmogorov turbulent atmosphere
摘要： Subcarrier intensity modulation (SIM) scheme is preferred due to efficient bandwidth usage superiority over other modulation techniques such as on–off keying (OOK), pulse position modulation (PPM). In this paper, we investigate the bit error rate (BER) performance of optical wireless communication (OWC) system using binary phase shift keying (BPSK) SIM in non-Kolmogorov turbulent atmosphere. We pay attention to the weak turbulence conditions by using Rytov approximation and considering that the receiver is a PIN photodetector. Propagating beam type is Gaussian. It is seen that BER performance of the BPSK SIM OWC is significantly affected from non-Kolmogorov power law exponent, load resistor, responsivity of the PIN photodetector, bandwidth, beam source size, turbulence strength and noise factor.
关键词： Subcarrier intensity modulation,Optical wireless communication,Bit error rate,Atmospheric turbulence
更新于2025-09-23 15:23:52
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Optical orbital angular momentum under strong scintillation
摘要： The evolution of classical optical fields propagating through atmospheric turbulence is investigated under arbitrary conditions. We use the single-phase screen (SPS) method and the infinitesimal propagation equation (IPE), a multiphase screen (MPS) method, to compute the optical power fractions retained in an input Laguerre-Gauss (LG) mode or transferred to higher-order LG modes. Although they show the same trend while the scintillation is weak, the IPE and SPS predictions deviate when the strength of scintillation passes a certain threshold. These predictions are compared with numerical simulations of optical fields propagating through turbulence. The simulations are performed using an MPS model, based on the Kolmogorov theory of turbulence, for different turbulence conditions to allow comparison in both weak and strong scintillation. The numerical results agree well with the IPE results in all conditions, but they deviate from the SPS results for strong scintillation.
关键词： multiphase screen method,scintillation,infinitesimal propagation equation,atmospheric turbulence,Laguerre-Gauss modes,single-phase screen method,optical orbital angular momentum
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Information and Communication Technology Convergence (ICTC) - Jeju (2018.10.17-2018.10.19)] 2018 International Conference on Information and Communication Technology Convergence (ICTC) - Performance of SIM/S-QAM FSO Systems with Phase Errors in Gamma-Gamma Turbulence Channels
摘要： In this paper, we study the performance of subcarrier intensity modulation (SIM) squared quadrature-amplitude modulation (S-QAM) free-space optical (FSO) communication systems considering the atmospheric turbulence-induced phase error in fading channel. The atmospheric fading channel is modeled by Gamma-Gamma distribution while the Tikhonov model is used for the turbulence-induced phase error. The numerical results quantitatively show the impact of atmospheric turbulence parameters to the performance of FSO systems in terms of average symbol-error probability (ASEP) and the power penalty. Besides, the theoretical results are validated through Monte Carlo simulation to confirm our analysis.
关键词： Free-space optics (FSO),Phase error.,Atmospheric Turbulence,Fading Channel,Squared quadrature-amplitude modulation (QAM)
更新于2025-09-23 15:22:29
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[IEEE 2018 Second International Conference on Electronics, Communication and Aerospace Technology (ICECA) - Coimbatore (2018.3.29-2018.3.31)] 2018 Second International Conference on Electronics, Communication and Aerospace Technology (ICECA) - FSO Link Performance Analysis with Different Modulation Techniques under Atmospheric Turbulence
摘要： Free space optics (FSO) has achieved prominence in extremely large bandwidth, unlicensed spectrum and low power secure transmission in the field of wireless communication. Despite the advantages, it is deeply impacted due to atmospheric turbulence and fog weather conditions. This paper considers different modulation schemes under the presence of atmospheric turbulence and fog conditions. The desired expression of bit error rate (BER) is obtained by modeling the turbulence as gamma-gamma distributed channel and under this channel condition, 16-PPM has provided better performance than other schemes. BER is considered for the channel performance evaluation. This analysis can help to adopt a modulation technique according to the channel condition.
关键词： Bit error rate (BER),gamma-gamma distribution,atmospheric turbulence,Free space optics (FSO),Meijer’s G function
更新于2025-09-23 15:21:21
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Geometric distortion correction of long-range imaging containing moving objects
摘要： Video sequences of long-range imaging are inevitably affected by optical turbulence, which leads to non-uniform geometric distortion and object position shifts. Restoration of this turbulence-degraded data containing moving objects is a challenging task, which essentially involves in video stabilization and moving objects detection. In this work, a novel method for simultaneously realizing turbulence mitigation and moving objects detection is proposed in such scenarios. We firstly model the turbulent foreground with a specific mixture of Gaussian (MoG) distribution, which is regularized online by the low-rank subspace of background. Furthermore, to well preserve the low-rank property of dynamic background, we embed a transformation operator into the proposed model which makes it much more robust in practical camera jitters or rotation. Finally, a simple mask strategy is used to reconstruct stable frame containing moving objects. Extensive experiments using synthetic and real-life turbulence-degraded data show that the proposed method outperforms other compared approaches in terms of both geometric distortion correction and moving objects preservation.
关键词： Image detection systems.,Image reconstruction-restoration,Imaging through turbulent media,Atmospheric turbulence
更新于2025-09-23 15:21:01
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Transmission characteristics of 24.5??Gb/s atmospheric laser communication based on optical frequency comb
摘要： Through cascading Mach–Zehnder intensity modulator (MZIM) and phase modulator (PM), an optical frequency comb (OFC) with 7 flat comb teeth is produced. The frequency interval of the OFC is 25 GHz and the flatness is less than 1.5 dB. The 7 channels of the OFC are used as the carrier source of the one-to-many free-space optical (FSO) communication system, and the atmospheric turbulence simulation pool is used to simulate the turbulence intensity in the real atmosphere to verify its feasibility for FSO communication. In the experiment, the bit error rate (BER) and eye diagram are measured under the back-to-back (BTB) conditions, and the temperature difference of atmospheric turbulence simulation pool are 80 ?C, 150 ?C and 220 ?C. Each channel of the system can stably transmit the on–off keying (OOK) signal of 3.5 Gb/s, and the 7 channels can stably transmit the OOK signal of 24.5 Gb/s. Thereby, the OFC can be used in place of multiple lasers or laser arrays as a carrier source for a one-to-many FSO communication system.
关键词： Wavelength division multiplexing,Optical frequency comb,Atmospheric turbulence,Free-space optical communication
更新于2025-09-23 15:19:57
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4-aperture differential image motion monitor as a new approach for estimating atmospheric turbulence parameters
摘要： The present study aims to evaluate the possibility of simultaneous measurements of Fried parameter and atmospheric Zernike defocus by measuring defocus aberration with 4-aperture differential image motion monitor (DIMM) for a portable telescope. Based on the results, a relation was observed between the variances of the defocus aberration (4-aperture defocus) and Fried parameter for G-tilt and Z-tilt methods. In addition, the variance of the 4-aperture defocus was compared with those of the Zernike defocus and the conventional DIMM and the results indicated a linear relationship. Based on the telescope and 4-aperture specifications, the variance of the 4-aperture defocus was converted into the Zernike defocus or the DIMM variances. Finally, the ability of estimating atmospheric coherence time by measuring the variance of the Zernike defocus velocity or the sum of the variances of two astigmatisms velocities with 4-aperture DIMM was investigated.
关键词： atmospheric defocus aberration,atmospheric turbulence parameters,Optical turbulence
更新于2025-09-19 17:15:36
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Multi-aperture fiber coherent combining system in urban horizontal atmospheric laser link
摘要： Multi-aperture receiver with optical combining architecture is an effective approach to overcome the turbulent atmosphere effect on the performance of the free-space optical (FSO) communications. In this paper, we built a 1 km urban horizontal link, and adopted beam combining system with four apertures at receiver. By analogy with aperture smoothing factor, we proposed the concept of fluctuation suppression ratio to evaluate the mitigation ability of the system on atmospheric fading. The experimental results confirmed that the beam combining system can perform best when the aperture interval is larger than the coherent length, and the performance decreases with the increase of the coherent length. Moreover, we found that the change of phase differences between the input beams is more than 40 ??rad, which provides reference for future system design.
关键词： Scintillation index,Atmospheric turbulence,Multi-aperture,Optical coherent combining
更新于2025-09-19 17:13:59
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Capacity analysis of free space optical communication system under atmospheric turbulence
摘要： In this paper, the analytical channel capacity of the free space optical (FSO) system under weak, moderate and strong turbulence is derived. The FSO channel statistics follows the log-normal distribution under weak turbulence and follows the Gamma–Gamma distribution under moderate and strong turbulence. The three generally used adaptive transmission schemes in FSO communication system are as follows (1) optimal simultaneous power and rate adaptation, (2) optimal rate adaptation with constant transmit power, and (3) truncated channel inversion with a fixed rate. The closed-form approximations for the average ergodic channel capacity for these adaptive transmission schemes under different atmospheric turbulence without any pointing error are derived. Simulation results depict the excellent agreement of the proposed analytical models with the Monte Carlo simulation.
关键词： Channel capacity,Free space optical communication,Signal to noise ratio,Adaptive transmission,Atmospheric turbulence
更新于2025-09-19 17:13:59
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Non-Kolmogorov atmospheric turbulence and orbital angular momentum of entangled states for optical communication
摘要： We extend the theory of detection probabilities of single-photon communication in turbulent atmosphere to the entangled case and derive analytical expressions for detection probabilities. We show that the rotational ?eld correlation in the entangled case cannot be expressed as a straightforward extension from the disentangled case. By considering the orbital angular momentum (OAM) entangled Laguerre-Gaussian (LG) beams for illustration, we explore the e?ect of non-Kolmogorov atmospheric turbulence on the probabilities of both the biphoton detection and the single-photon detection. The entanglement of OAM LG beams contributes positively to the faithful detection probability. The change of maximal crosstalk probability in the detection process is also explored, which displays the non-linear dependence on the crosstalk quantum number.
关键词： Atmospheric turbulence,Orbital angular momentum,Entanglement,Optical communication
更新于2025-09-19 17:13:59