- 标题
- 摘要
- 关键词
- 实验方案
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Transmit laser selection for two hop decode and forward FSO communication with pointing errors
摘要： In this letter, two systems have been proposed for efficient unidirectional free space optical (FSO) cooperative communication-one with only transmit laser selection (TLS) and the other using optical spatial modulation (OSM) along with TLS. Performance analysis of such systems for Gamma-Gamma (G-G) fading channels both with and without Pointing errors have been carried out in terms of outage probability and average symbol error probability (ASEP). Our proposed TLS system over G-G channel (with pointing error) yields a signal to noise ratio (SNR) gain of at least 10 dBm over the conventional FSO system.
关键词： cooperative communication,Free space optical communication,transmit laser selection,pointing errors,Gamma-Gamma fading,optical spatial modulation
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM) - Hong Kong, China (2019.7.8-2019.7.12)] 2019 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM) - Closed loop controlled optical tracking module for free-space optical communications
摘要： In this paper, a closed loop controlled optical tracking module for free-space optical communication is presented. The motion of the optical tracking module is achieved using a pan-tilt mechanical platform driven by two servomotors. The optical tracking module consists of optical elements including beam splitters and quadrant photodiodes to extract the angular parameters of the incident wave. Optical as well as dynamic modeling is performed to confirm the tracking functionality of the system. Furthermore, to validate the concept, experimentation has been carried out by placing a laser emission module in front of a fixed optical tracking module. The laser was moved in free-space with the help of a mechanical structure and the successful tracking of the optical tracking module has been observed.
关键词： pan-tilt mechanical platform,servomotors,quadrant photodiodes,beam splitters,optical tracking module,free-space optical communication
更新于2025-09-12 10:27:22
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Novel OCDMA Schemes in Free Space Optical Communication Networks: Performance Evaluation and Comparative Analysis
摘要： Free space optical (FSO) communication based networks are constrained due to the atmospheric turbulence, which limits the achievable data rates. Employing code-division multiple-access (CDMA) with FSO system can provide a feasible solution for seamlessly multiplexing a large number of users. The CDMA data can be with negative polarity, and thus for intensity modulation over optical links, usually a suitable DC bias is added to the CDMA data. We refer to this scheme as DC biased Optical CDMA (DC-OCDMA). It, however, also requires a higher bit energy. We propose two novel OCDMA (OCDMA) schemes, viz., dual wavelength OCDMA (DW-OCDMA) and wavelength diversity OCDMA (WD-OCDMA) to improve the Eb/No penalty incurred due to DC-OCDMA scheme. The first scheme utilizes two wavelengths for separating positive and negative data of the CDMA, and the second scheme exploits diversity. We compare the performance of the proposed schemes with the DC-OCDMA technique in different turbulence regimes and show that the WD-OCDMA scheme outperforms the DC-OCDMA scheme in all turbulence regimes whereas DW-OCDMA scheme outperforms DC-OCDMA scheme in moderate and low turbulence regimes. Moreover, out of the two proposed techniques, the WD-OCDMA gives higher Eb/No gain than the DW-OCDMA scheme in moderate and high turbulence regimes whereas DW-OCDMA scheme outperforms the WD-OCDMA scheme in low turbulence regime.
关键词： bit error rate,optical code division multiple access,free space optical communication
更新于2025-09-12 10:27:22
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Exact distributions for bit error rate and channel capacity in free-space optical communication
摘要： Bit error rate (BER) and channel capacity are two important metrics to assess the performance of free-space optical communication (FSOC) systems. Due to the fading of the optical signal owing to the atmospheric effects, these two quantities behave as random variables. Most of the studies in this direction have focused on the calculation of only the average of these quantities. However, since the complete information about a random variable is encoded in its distribution, it is more informative to examine the latter itself. In this work, the authors derive exact probability density function (PDF) expressions for the BER and the channel capacity for an arbitrary irradiance model. In particular, they investigate these exact results for log-normal, gamma-gamma, and K distributions. For the BER analysis, they focus on the binary phase shift keying and quadrature phase shift keying modulation schemes. The authors' analytical reults are found to be in conformity with Monte Carlo simulations. The exact PDFs of the BER and the channel capacity reveal that there are several instances when the average is unable to capture the actual behaviour of these quantities, and therefore one must be careful in drawing conclusions based on the first moment only.
关键词： binary phase shift keying,bit error rate,quadrature phase shift keying,gamma-gamma distribution,channel capacity,log-normal distribution,K distribution,probability density function,free-space optical communication
更新于2025-09-12 10:27:22
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A UAV-Mounted Free Space Optical Communication: Trajectory Optimization for Flight Time
摘要： In this work, we address the trajectory optimization of a fixed-wing unmanned aerial vehicle (UAV) using free space optical communication (FSOC). Here, we focus on maximizing the flight time of the UAV by considering practical constraints for wireless UAV communication, including limited propulsion energy and required data rates. We find optimized trajectories in various atmospheric environments (e.g., moderate-fog and heavy-fog conditions), while also considering the channel characteristics of FSOC. In addition to maximizing the flight time, we consider the energy efficiency maximization and operation-time minimization problem to find the suboptimal solutions required to meet those constraints. Furthermore, we introduce a low-complexity approach to the proposed framework. In order to address the optimization problem, we conduct a bisection method and sequential programming and introduce a new feasibility check algorithm. Although our design considers suboptimal solutions owing to the nonconvexity of the problems, our simulations indicate that the proposed scheme exhibits a gain of approximately 44.12% in terms of service time when compared to the conventional scheme.
关键词： trajectory design,Free space optical communication (FSOC),wireless communications with an unmanned aerial vehicle (UAV),flight time maximization,UAV-mounted FSOC
更新于2025-09-12 10:27:22
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[IEEE OCEANS 2019 - Marseille - Marseille, France (2019.6.17-2019.6.20)] OCEANS 2019 - Marseille - Multi-laser Transmissometer for Ocean Optical Classification and Biofouling Detection
摘要： This research and development effort designs and tests new multi-laser transmissometer algorithms and hardware for ocean optical classification and autonomous biofouling detection. The system expands the collection of inherent optical properties and enables in-situ wavelength optimization for future optical communication links. Undersea testing succeeded and was contingent on several accomplishments, including developing robust algorithms, integrating opto-electronics within a custom chassis, and engineering a handheld-sized pressure vessel suitable for diverse field experimentation. The project verifies the feasibility of key enablers—autonomy, environmental classification, biofouling detection, and laser propagation—for remote undersea platforms with low size, weight, and power.
关键词： sensing,propagation,lasers,autonomy,underwater,undersea,oceanography,optimization,free space optical communication
更新于2025-09-12 10:27:22
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Free Space Optical Communication (System Design, Modeling, Characterization and Dealing with Turbulence) || 2. Real-time measurement of meteorological parameters for estimating low altitude atmospheric turbulence strength (C2 n)
摘要： The major factor that limits the performance of Free Space Optical Communication (FSOC) is atmospheric turbulence which fluctuates over time in accordance with the variations in local meteorological parameters. Estimating the atmospheric turbulence strength (C2n) from measurement data is significant for finding the data rate the system is capable of operating at under different outdoor local environmental conditions. Hence, a low cost customized system for continuously measuring local meteorological data is developed and presented in this chapter. A field test scintillometer setup is established for a link range of 0.5 km at an altitude of 15.25 m. Specialized sensors are interfaced to the digital architectures to acquire the real-time data corresponding to atmospheric changes. The accuracy and performance of the measurement system are tested against standard instruments and the maximum correlation coefficients of 99.92 %, 99.63 %, 99.73 %, and 99.88 % are achieved for wind speed, temperature, relative humidity and pressure respectively. Atmospheric turbulence strength is estimated for the diurnal period using measured meteorological data. The validations of the estimated results with the scintillometer measurement are also analyzed. The weather profile and corresponding C2n variations at our test field for different seasons over a one year period are presented and the results are analyzed.
关键词： atmospheric turbulence,meteorological parameters,scintillometer,PAMELA model,Free Space Optical Communication (FSOC)
更新于2025-09-12 10:27:22
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Free Space Optical Communication (System Design, Modeling, Characterization and Dealing with Turbulence) || 6. Quality metrics and reliability analysis of ground-to-ground free space laser communication in different weather conditions together with beam steering system
摘要： Over the past two decades Free Space Optical Communication (FSOC) has become more and more interesting as an adjunct or alternative to Radio Frequency (RF) communication. Optical wave propagation in an FSOC channel is severely affected by turbulent atmospheric parameters and they lead to the degradation of the data transmission quality and reliability. Among the various atmospheric effects, beam wandering is the main cause for major power loss and cannot be solved without incorporation of a Beam Wandering Compensation (BWC) control system. Therefore, a closed form treatment describing beam wandering effect mitigation is required. Simplex FSOC data transmission (data rate is 155 Mbps) transmitter-receiver experimental setups are established for the data link range of 0.5 km at an altitude of 15.25 m at the college campus. A near IR 850 nm optical source is used for data transmission. The more accurate values of atmospheric attenuation (Atten) and turbulence strength (C2n) are obtained using the new models developed according to local weather data. The transmittance of the FSOC channel is calculated using the estimated atmospheric attenuation. The methods of measuring the Q-factor and Bit Error Rate (BER) by postprocessing the received signal are described and used to validate the performance of the FSOC system. The improvements on received signal strength and centroid stability by incorporating the BWC control system are analyzed with various communication key parameters in the very weak to very strong atmospheric turbulence conditions. The average BER at a value of 9.82 ? 10?9 is maintained with the Q-factor value of ≈ 6 in almost all atmospheric turbulence conditions with compensating beam wandering effects, i.e. pointing error losses. Evidence of the suitability and effectiveness of the developed controller in terms of received power (Pr), transmittance (T), eye diagram, Q-factor, Signal to Noise Ratio (SNR), BER, link margin and decoding decision threshold values are comprehensively analyzed through experimental results and reported in this chapter.
关键词： atmospheric turbulence,Beam Wandering Compensation (BWC),Q-factor,Signal to Noise Ratio (SNR),Bit Error Rate (BER),Free Space Optical Communication (FSOC)
更新于2025-09-12 10:27:22
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Performance analysis of 349-element adaptive optics unit for a coherent free space optical communication system
摘要： As a continuation of our previous work [Optics Express.25, 15229(2017)] in which we have verified the performance of a coherent free space optical communication (FSOC) system with a 97-element adaptive optics (AO) system, in this paper, we evaluated the performance improvement of the coherent FSOC system using a large-scale high-speed AO system with a 349-element continuous surface deformable mirror. The mixing efficiency (ME) and bit-error-rate (BER) under different Greenwood frequency (GF) were calculated as the performance metric of coherent FSOC system. The performance of FSOC system using such a large-scale AO system was quantitatively verified for the first time. The obtained results showed that the performance was obviously improved when a larger-scale high-speed AO system is employed in coherent FSOC system. This analysis result provides a performance verification for large-scale high-speed AO systems used in FSOC system which is beneficial for coherent FSOC system parameters design.
关键词： bit-error-rate,adaptive optics,free space optical communication,coherent detection,mixing efficiency
更新于2025-09-11 14:15:04
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Use of Same WDM Channels in Fiber Network for Bidirectional Free Space Optical Communication With Rayleigh Backscattering Interference Alleviation
摘要： In the paper, we present and demonstrate experimentally a 10 Gbit/s on-off keying (OOK) bidirectional wavelength-division-multiplexing (WDM) free space optical (FSO) communication architecture integrated in fiber network together with 5 m free space transmission length and 25 km fiber link, respectively. To achieve bidirectional FSO link, the all WDM wavelengths can be used simultaneously to serve as the downstream and upstream traffics in the proposed FSO-WDM system. Here, four pairs of line terminations (LTs) and optical wireless units (OWUs) are integrated arbitrarily in fiber access network for confidential and bidirectional FSO connection based on the requirement of practical environment. In the measurement, the relationship of FSO signal performance and detected tolerance are also discussed and analyzed. Moreover, the WDM-FSO transmission can also avoid the Rayleigh backscattering (RB) beat noise in fiber connection.
关键词： Free space optical communication,wavelength-division-multiplexing (WDM),Rayleigh backscattering (RB)
更新于2025-09-11 14:15:04