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Performance Limits of FSO Based SAC-OCDMA System Under Weather Conditions
摘要： In this paper, the Spectral Amplitude Coding Optical Code Division Multiple Access (SAC-OCDMA) is investigated in Free Space Optics (FSO) using Zero Cross Correlation (ZCC) codes to evaluate its performance limits in terms of link range. The system is analyzed under clear, haze, moderate fog and dense fog weather conditions. This system has been evaluated numerically and by simulation analysis by maintaining the transmitted power at 10 dBm, for safety reason, according to International Telecommunication Union (ITU) and minimum acceptable BER of 10–9. The simulation results shown that the present system can transmit 622 Mbps/1 Gbps up to maximum link range of 1450 m/1100 m and 61 m/54 m under clear and dense fog conditions, respectively.
关键词： fog,haze,free space optic (FSO),spectral amplitude coding optical code division multiple access (SAC-OCDMA),zero cross-correlation (ZCC)
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Current Trends towards Converging Technologies (ICCTCT) - Coimbatore, India (2018.3.1-2018.3.3)] 2018 International Conference on Current Trends towards Converging Technologies (ICCTCT) - Impact of Modulation Techniques for Hybrid-WDM Based FSO
摘要： Free space optical communication (FSO) provides high data rate by allowing light passed through the atmosphere. It is very effective and efficient technology for wireless communication. This emerging field basically uses invisible beams of light such as ultraviolet, infrared, etc. This work exclusively deals with the designing of hybrid WDM based FSO system using the simulation software Opti-System 7.0 with Minimum-Shift Keying and Differential-phase-shift keying. Further their study has been made as to which modulation techniques provides better means of communication. The normal rain weakening from rain power information which are gathered for a period for six months. The concert of the future system is evaluated in terms of Bit Error Rate, Q-factor, and Receiver Sensitivity are examined with respect to link distance for using rain attenuation 20.5dBm. The transmission wavelength and data rate is 1550nm and 2.5Gbps considered for investigation.
关键词： Receiver Sensitivity,Hybrid WDM,BER,Free space optical communication,DPSK,MSK
更新于2025-09-23 15:23:52
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An 82-m 9 Gb/s PAM4 FSO-POF-UWOC Convergent System
摘要： With the increasing demands in free-space/underwater environmental monitoring, disaster precaution, and manufacturing industry applications, free-space optical (FSO)-plastic optical fiber (POF)-underwater wireless optical communication (UWOC) convergence is designed to be a promising framework for providing long-haul free-space with underwater links. An 82-m 9 Gb/s four-level pulse amplitude modulation (PAM4) system employing a 405-nm blue-light injection-locked laser diode (LD) is thereby offered and practically demonstrated. Results reveal that a 1.8-GHz 405-nm blue-light injection-locked LD can be effectively applied for a 9 Gb/s PAM4 signal transmission over 50 m FSO link, 30 m graded-index (GI)-POF transportation, and 2 m clear ocean underwater channel. To the authors’ understanding, this study is the first to practically build an 82-m 9 Gb/s PAM4 FSO-POF-UWOC convergent system that effectively constructs a long-haul optical wireless-wired-wireless link using doublet lenses, GI-POF, and optical beam reducer. The performances of the proposed convergent systems are analyzed by bit error rate and non-return-to-zero eye diagram in real-time over an 82-m transport. This framework is the leading one to establish a long-haul FSO-POF-UWOC convergent system with qualified transmission performances. It guides a promising way to facilitate wide applications in the convergence of FSO, POF and UWOC.
关键词： Graded-index plastic optical fiber,Underwater wireless optical communication,Four-level pulse amplitude modulation,Free-space optical
更新于2025-09-23 15:23:52
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Performance Evaluation of Hybrid FSO-SACOCDMA System under Different Weather Conditions
摘要： Spectral amplitude coding optical code division multiple access (SACOCDMA) is a multiplexing technique, which provides faster speed, efficiency, security and unlimited bandwidth. It is widely preferred because of its ability to eliminate multiple access interference (MAI). Free space optics (FSO) provides a wireless link to transmit data securely at higher rates for last mile access. In this work, a 100 Gb/s hybrid FSO-SACOCDMA is designed using direct detection. The performance of FSO using SACOCDMA utilizing NZCC (New Zero Cross Correlation) code is evaluated under different weather conditions (clear weather, haze and fog) for ten users where each user carries 10 Gb/s. The results indicate that in clear weather FSO distance can be extended up to 13 km. Moreover, after using pre-amplifier in clear weather, FSO enhances the maximum distance to 35 km with acceptable signal to noise ratio and bit error rate. Using an amplifier in the link not only makes the quality of the signal better but it also increases the communication range.
关键词： spectral amplitude coding optical code division multiple access (SACOCDMA),free space optics (FSO),direct detection (DD),new zero cross correlation (NZCC)
更新于2025-09-23 15:23:52
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Aberrated Microlenses to Reduce Crosstalk in Free Space Optical Interconnects Systems
摘要： A free space optical interconnects system that uses Gaussian beams and focusing microlenses with spherical aberration has been considered. Numerical results show that the use of microlenses with negative spherical improves the signal-to-crosstalk ratio of the interconnects system at some optimum positions of the detector array. An expression for output field at the detectors plane is derived and used to evaluate the signal-to-crosstalk ratio.
关键词： lens spherical aberration,optical crosstalk,free space optical interconnects
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Intelligent and Innovative Computing Applications (ICONIC) - Mon Tresor, Plaine Magnien, Mauritius (2018.12.6-2018.12.7)] 2018 International Conference on Intelligent and Innovative Computing Applications (ICONIC) - Climatic Effects on Free Space Optics Link: South African Climate
摘要： The growth in demand of high data rate, reliable quality of service, low cost technology and secured connectivity have been telecommunication users' concerns. Free Space Optics (FSO) is the best choice for meeting these demands as it offers data rates in Gbps with the most secure communication because light beam is prone to eavesdropping. However, usage of FSO as a communication link relies upon local weather condition. Atmospheric attenuation of fog, rain and snow are the most limitation of free space optic availability, as they lead to the diminution of limited available bandwidth. This paper investigated the link performance under climatic conditions such as fog, rain and snow by at various wavelengths of 650nm, 750nm, 850nm, 950nm and 1550nm. It is further deals with FSO performance targeting to acquire minimal Bit Error Rate (BER), suitable transmitting power, optimum link margin and reliable data transmission rate at maximum link distance of 1km. The studies observed that received power signal and the link distance have an inverse correlation because once the signal reaches to an extended distance; it faces greater climatic attenuation due to scattering and absorption lessening.
关键词： communication link,Free space optics,atmospheric attenuation,light beam,bit error rate
更新于2025-09-23 15:22:29
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[IEEE 2018 International Conference on Intelligent and Innovative Computing Applications (ICONIC) - Mon Tresor, Plaine Magnien, Mauritius (2018.12.6-2018.12.7)] 2018 International Conference on Intelligent and Innovative Computing Applications (ICONIC) - Atmospheric Effects on Free Space Optics Wireless Communication: Applications and Challenges
摘要： Demand for data and multi-media services in recent times has really grown and it is expected to grow more in the next decade with application ranges from high speed real-time/live streaming to live video-conferencing, and so the demand for new and richer data services to meet up with the new and more advanced applications. In other to meet up with these great users’ expectations, there is a need to explore other viable access network technologies that can offer services beyond what is already in the offering. Free space optical (FSO) communication system is the predominant choice to replace existing wireless technology with great availability of link capacity and huge bandwidth to meet the user’s expectation of the 21st century. This system is reliant on optics signal transmitted in a free space channel, hence termed FSO. This type of communication does not require any licenses for its operation and offers many features being the low-start up and operational cost, rapid development and high fiber-like bandwidth. FSO uses line-of-sight path for the communication between two points and beam of light to provide optical connection that can send and receive video, voice and data information. This technology provides a massive and unregulated bandwidth where a data rate in excess of 100Gbit/s is achievable over a distance of 1-4km. However, it suffers from degradation in the signal quality due to its susceptibility to atmospheric channel impairments which limits its wide deployment and quality of services. This paper explores the FSO system, atmospheric effects of implementing this system and mitigating techniques.
关键词： free space optical fiber-like,atmospheric channel,real-time,multi-media
更新于2025-09-23 15:22:29
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Physical Layer Security of Hybrid Satellite-FSO Cooperative Systems
摘要： In this paper, we study the physical layer secrecy performance of a hybrid satellite and free-space optical (FSO) cooperative system. The satellite links are assumed to follow the Shadowed-Rician fading distribution; and the channel of the terrestrial link between the relay and destination is assumed to experience the Gamma-Gamma fading. For the FSO communications, the effects of different types of detection techniques (i.e., heterodyne detection and intensity modulation with direct detection) as well as the pointing error are considered. We derive exact analytical expressions for the average secrecy capacity (ASC) and secrecy outage probability (SOP) for both cases of Amplify-and-Forward (AF) and Decode-and-Forward (DF) relaying. The asymptotic analysis for the SOP is also conducted to provide more insights on the impact of FSO and satellite channels on secrecy performance. It is found that with the AF with fixed gain scheme, the secrecy diversity order of the investigated system is only dependent on the channel characteristics of the FSO link and the FSO detection type, whereas the secrecy diversity is zero when the relay node employs DF or AF with variable-gain schemes.
关键词： land mobile satellite (LMS) channel,secrecy outage probability,hybrid satellite free-space optical (FSO) cooperative system,Physical layer security,average secrecy capacity
更新于2025-09-23 15:22:29
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Modeling of Short-Range Ultraviolet Communication Channel Based on Spherical Coordinate System
摘要： The study on short-range ultraviolet (UV) communication (UVC) channel modeling is often based on prolate-spheroidal coordinate system in previous studies. In this letter, we propose a single scattering coplanar model based on spherical coordinate system, where the transmitter beam and receiver field of view (FOV) can point arbitrarily under the limitation that the sum of transceiver elevation angles and half of their own FOV is less than 180°, and the transmitter beam and receiver FOV are above ground. We utilize the number of intersections between a special ray on the transmitter cone and the receiver conical surface to distinguish the UVC scenarios, which makes the analysis of UVC channel modeling comprehensible. Meanwhile, we validate the proposed model in comparison with the single scattering model and the Monte Carlo simulation model through numerical calculations. The results show that the proposed model agrees well with the both models. This work presents a new method to estimate the path loss of short-range UVC and provides guidelines for the experimental system design.
关键词： ultraviolet communications,Atmospheric propagation,free-space optical communication
更新于2025-09-23 15:22:29
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-Distribution Dual-Hop RF/FSO Systems
摘要： In this correspondence, we investigate the physical-layer security of a mixed radio frequency/free space optical (RF/FSO) dual-hop communication system for both fixed- and variable-gain relaying schemes. More specifically, we only assume that the eavesdropping happens at the RF link because the optical link has high security. We assume that all RF channels suffer from η–μ fading, while the FSO link experiences M-distributed fading. Then, we derive some analytical results for the average secrecy rate and the secrecy outage probability.
关键词： secrecy outage probability,Average secrecy rate,radio frequency-free space optical,M-distributed fading,η-μ fading,physical-layer security
更新于2025-09-23 15:22:29