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Green Underwater Communication Systems
Published in Gurjit Kaur, Akanksha Srivastava, Green Communication Technologies for Future Networks, 2023
Dushyant Singh Chauhan, Gurjit Kaur, Dinesh Kumar
Optical wireless communication offers several significant benefits, including extremely high data transmission rates, small and light transceiver components, secure communication links, and low operational costs (Prasad et al. 2005). To perform communication for short, medium, or long-range, optical wireless technology utilized modulated optical beams. In the visible spectrum (i.e., 400–700nm), optical waves give an alternate method of providing high data rates in the water. That is why optical underwater wireless communication has attracted a lot of attention in recent years as a high-speed (10–100 Mbps), secure, and dependable alternative to conventional acoustic underwater communications systems (Darwiesh et al. 2018).
Atmospheric Transmission Limitations
Published in Roberto Ramirez-Iniguez, Sevia M. Idrus, Ziran Sun, Optical Wireless Communications, 2008
Roberto Ramirez-Iniguez, Sevia M. Idrus, Ziran Sun
Optical wireless communication systems are affected by a variety of atmospheric phenomena that limit their data transmission rate, range, and reliability. In the case of outdoor systems, atmospheric phenomena such as haze, fog, rain, and scintillation have a detrimental effect on their performance. From these, fog and haze constitute the most important atmospheric scatterers. Their attenuation, which can reach values of over 300 dB/km (corresponding to very thick fog), can affect the performance of a wireless IR link for distances as small as 100 m. A similar effect occurs when smoke is within the communication path.
Time jitter influence on the performance of gamma–gamma turbulence FSO links with various modulation schemes
Published in Journal of Modern Optics, 2020
G.D. Roumelas, H.E. Nistazakis, W. Gappmair, P.J. Gripeos, V. Christofilakis
Optical wireless communication systems attracted significant research interest over the last years, which is mainly due to the low installation and operational costs and the huge data rates they can achieve because of their very high bandwidth. Furthermore, the operation of such links is secure and not compromised by regulatory and license problems [1–5].
Multimode laser beam scintillations in weak atmospheric turbulence for vertical link laser communications
Published in Waves in Random and Complex Media, 2022
Ömer F. Sayan, Hamza Gerçekcioğlu, Yahya Baykal
Optical wireless communication links are advantageous over the alternative conventional communication links mainly because of the possibility of using very high data bit rates. However, optical wireless communication links also have some disadvantages due to the degrading effects of turbulence, haze, fog, rain and snow. Such atmospheric conditions will lower the performance of information transfer, and can even break the communication links [1–3]. There are intense studies that seek to reduce the effects of the stated atmospheric conditions. In this respect, the effects of turbulence, as well as the other effects, on the system performance, are carried out using various laser beam models [3–11]. The reflection of these beam patterns to the optical communication technologies and the ways and methods to mitigate the fluctuation of atmospheric effects are investigated under different atmospheric conditions [12–23]. In addition to the studies done for the horizontal link where the structure parameter is constant, the effect of atmospheric turbulence and beam models are extensively studied also for slant and vertical links [24–29]. Furthermore, system performances have been examined for many years in aeronautical and satellite links where one of the important events leading to degradation is the atmospheric turbulence [3, 30–37]. Type of multimode models was also analyzed in previous studies [38–40], which brings the inspiration to adapt these works in vertical bidirectional links. Examination of the on-axis scintillation indices in weak atmospheric turbulence, by using the Rytov method will give us the clue to understand how effective will the multimode excitation be in aerial vehicle laser communications, especially in unmanned aerial vehicle (UAV) and satellite optical communication systems in which the transmitter and the receiver are operating in between the ground to near earth and earth orbit satellite, and near earth and orbit satellite to ground. In this context, in vertical optical communications, the flat-topped beam is scrutinized for aeronautical laser communication systems, and annular beam model is examined for satellite communication systems, operating in vertical paths having weak atmospheric turbulence [31,32]. In these earlier works, bit error rate (BER) performances of such links are analyzed by using Rytov method.
Signal-to-noise ratio with adaptive optics compensation in non-Kolmogorov weak turbulent atmosphere
Published in Waves in Random and Complex Media, 2021
Yalçın Ata, Yahya Baykal, Muhsin Caner Gökçe
Atmospheric turbulence imposes a significant limitation on the propagation of optical waves and degrades the performance of the optical wireless communication (OWC) systems. Atmospheric turbulence draws the attention of researchers and many studies are being done to accurately define the turbulence characteristics. A large number of space, military, airborne and ground-based wireless large bandwidth and high capacity communication systems are reported recently. OWC systems suffer from both intensity and phase fluctuations originating from atmospheric turbulence causing distortion in the wavefront at the receiver. Other phenomena such as scattering and absorption also cause attenuation of the optical received power. The atmospheric turbulence is statistically modeled usually by Kolmogorov turbulence spectrum. Some research results revealed that the atmospheric turbulence presents a different spectrum of refractive index fluctuations in the inertial range than the one proposed by Kolmogorov. Many studies have been devoted to investigate the scintillation [1–5], intensity [6–8], transmittance [9–11], beam spreading [12–14] and beam wander [15–17] for different beam types propagating in both Kolmogorov and non-Kolmogorov turbulent atmosphere. Moreover, the influence of atmospheric turbulence on the performance of the OWC systems that is measured by the bit-error-rate (BER) [18–22] has been investigated in various studies. All results from these studies show that atmospheric turbulence, from weak to strong regime, gradually degrades the performance of OWC systems, and designers have to pay attention to the turbulence effects for the optimum design. Signal-to-noise ratio (SNR), impacting BER, is one of the most important metrics that show how the performance of an OWC system is affected by atmospheric conditions and internal circuit noise in receiver hardware. The SNR variation for the heterodyne lidar system [23] and the image spectrum SNR improvement [24] have been studied in terms of atmospheric turbulence conditions. Moreover, the SNR for an OWC system using plane wave in both weak and strong turbulent regimes has been assessed versus the link length and turbulence strength [25]. In Reference [26], the SNR variation for a Gaussian beam in anisotropic and isotropic turbulence has been examined but the results have been obtained without the calculation of SNR in the absence of the atmospheric turbulence where values were imposed externally. All the results show that turbulence deteriorates the SNR, hence impairs the performance of the OWC system. In Reference [27], the average optical transfer function and the SNR performance of an image measurement and postprocessing technique are reported.