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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 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - Singapore, Singapore (2019.8.28-2019.8.30)] 2019 IEEE 16th International Conference on Group IV Photonics (GFP) - A Compact Circuit Model for Si-Ge Avalanche Photodiodes over a Wide Range of Gain
摘要： A Si-Ge avalanche photodiode circuit model is demonstrated, which includes carrier transit time, avalanche buildup time, and electrical parasitics. Electrical and optical dynamics are accurately captured over a wide range of gain. Excellent matching between simulated and measured 50 Gb/s PAM4 eye diagrams is achieved.
关键词： Avalanche photodiodes (APDs),Optical communication,Modeling
更新于2025-09-12 10:27:22
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Fiber Optic and Atmospheric Optical Communication || Fading in Optical Communication Channels
摘要： As was mentioned in [1, 2], in most optical wired and wireless systems operated in the atmosphere [3, 4], there occur multiple diffraction, multiple reflection, and multiple scattering effects, due to artificial features inside fibers and dispersion of the inner material, or due to natural obstructions (aerosols, hydrometeors, such as rain, snow and clouds, etc.) filled in the atmosphere. All these effects, which cause not only addition losses (with respect to those obtained in line-of-sight [LOS] above-the-terrain conditions) but also addition fading of the signal strength observed at the detector, can be separated into two independent effects, the slow and the fast fading [5–10]. In real situations occurring in the atmospheric communication links, the various optical signals arriving at the moving or stationary detector via their respective paths have individual phases, which change continuously and randomly. Therefore, both the resultant signal envelope and its phase will also be random variables. Moreover, the Doppler effect can also be explained by random frequency modulation [11–14] due to different Doppler shifts of each of the received signals as multi-ray components. Therefore, to describe slow and fast signal fading, we need to introduce the corresponding mathematical description of the statistical effects that accompany real signal fading in multipath communication channels.
关键词： statistical description,optical communication,Doppler effect,multipath,fading
更新于2025-09-12 10:27:22
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Fiber Optic and Atmospheric Optical Communication || Atmospheric Communication Channels
摘要： The atmosphere is a gaseous envelope that surrounds the Earth from the ground surface up to several hundred kilometers. The atmosphere consists of different kinds of gaseous, liquid, and crystal structures, including effects of gas molecules (atoms), aerosol, cloud, fog, rain, hail, dew, rime, glaze, and snow. Except for the first two, the others are usually called hydrometeors in the literature. Furthermore, due to irregular and sporadic air streams and motions, that is, irregular wind motions, chaotic structures defined as atmospheric turbulence are also present in the atmosphere.
关键词： Hydrometeors,Atmosphere,Aerosol,Turbulence,Optical Communication
更新于2025-09-12 10:27:22
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Optical Fiber and Wireless Communications || OFDM Systems for Optical Communication with Intensity Modulation and Direct Detection
摘要： Intensity modulation and direct detection (IM/DD) is a cost-effective optical communication strategy which finds wide applications in fiber communication, free-space optical communication, and indoor visible light communication. In IM/DD, orthogonal frequency division multiplexing (OFDM), originally employed in radio frequency communication, is considered as a strong candidate solution to combat with channel distortions. In this research, we investigate various potential OFDM forms that are suitable for IM/DD channel. We will elaborate the design principles of different OFDM transmitters and investigate different types of receivers including the proposed iterative receiver. In addition, we will analyze the spectral efficiency and decoding complexities of different OFDM systems to give a whole picture of their performance. Finally, simulation results are given to assess the detection performance of different receivers.
关键词： modulation,detection,OFDM,optical communication,IM/DD
更新于2025-09-12 10:27:22
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Ultracompact and Unidirectional On-Chip Light Source Based on Epsilon-Near-Zero Materials in an Optical Communication Range
摘要： An on-chip light source is one of the essential components for integrated photonic circuits and quantum-information processing chips. To date, it has been a great challenge to construct an on-chip light source with high directionality, high collection efficiency, and ultrasmall feature size simultaneously in the optical communication range. Here, an on-chip light source, consisting of a circular paraboloid etched in an aluminum-doped zinc-oxide film, which is an epsilon-near-zero material, is experimentally realized at 1550 nm. Photons emitted from the a PbS quantum-dot cluster placed near the focal point of this paraboloid are reflected into a directional parallel beam due to the large impedance mismatch between aluminum-doped zinc oxide and ambient medium. An ultrasmall emission divergence angle of only ±3°, and an ultrahigh directional emission contrast ratio of 44 dB are achieved from the ultracompact device with a feature size of only 1.5 μm. Also, an ultrahigh collection efficiency of up to 92% is predicted by simulation. This work not only opens an alternative way for the realization of integrated photonic devices based on epsilon-near-zero materials, but also provides another method for the precise assembling of composite functional nanostructures.
关键词： nanomanipulation,on-chip light source,optical communication,epsilon-near-zero materials,quantum dots
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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Adaptive Equalization for Dispersion Mitigation in Multi-Channel Optical Communication Networks
摘要： Optical communication networks (OCNs) provide promising and cost-effective support for the ultra-fast broadband solutions, thus enabling them to address the ever growing demands of telecommunication industry such as high capacity and end users’ data rate. OCNs are used in both wired and wireless access networks as they offer many advantages over conventional copper wire transmission such as low power consumption, low cost, ultra-high bandwidth, and high transmission rates. Channel effects caused by light propagation through the fiber limits the performance, hence the data rate of the overall transmission. To achieve the maximum performance gain in terms of transmission rate through the OCN, an optical downlink system is investigated in this paper using feed forward equalizer (FFE) along with decision feedback equalizer (DFE). The simulation results show that the proposed technique plays a key role in dispersion mitigation in multi-channel optical transmission to uphold multi-Gb/s transmission. Moreover, bit error rate (BER) and quality factor (Q-factor) below 10?5 and above 5, respectively, are achieved with electrical domain equalizers for the OCN in the presence of multiple distortion effects showing the effectiveness of the proposed adaptive equalization techniques.
关键词： decision feedback equalizer,polarization mode dispersion,chromatic dispersion,feed forward equalizer,optical communication networks
更新于2025-09-12 10:27:22