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Distributed Sensor Arrays
Published in Prabhakar S. Naidu, Distributed Sensor Arrays Localization, 2017
Free-space optical communication provides an attractive alternative to wireless communication. Laser diodes and mirrors can be made very small, of the order –0.03 µm3. Another advantage of optical communication is low power decay, of the order ∝ 1/distance2. There are many other benefits accruing from the use of optical communication. The only disadvantage is the need for line-of-sight communication. There are two approaches to free-space optical communication: the passive reflective system and the active-steered laser system.
Insensitivity of partially coherent Gaussian -Schell model beams to the impact of dynamic Kolmogorov type turbulence
Published in Journal of Modern Optics, 2023
Lekshmi S.R., Dinesh N. Naik, C.S. Narayanamurthy
With the invention of the laser, free-space optical communication underwent a paradigm shift. The extreme directionality of laser beams enhanced the range and quality of data transmission. However, since the beam must pass through several kilometres of atmosphere, the quality of communication is still compromised [1] due to the atmosphere-induced turbid or turbulence effects on propagating beams. The result of these impacts is manifested as intensity fluctuations (scintillations), beam wandering, and beam spreading which in turn hinders the quality of data transmission [2–4]. These atmosphere-induced distortions can be corrected using adaptive optics systems. An adaptive optics system uses the phase conjugation technique to reconstruct a wavefront devoid of aberrations [5]. However, a real adaptive optics system demands highly sophisticated equipment with moving mechanical parts and high-end computational power. Due to these issues, real-time sensing and wavefront corrections in a closed-loop are nearly impossible to achieve for stronger turbulence. An altogether different approach to looking at the problem would be the optimization of optical beams at the transmitter end. Different methods have been employed to fine-tune the transmitting beam characteristics, such as altering its degree of coherence and degree of polarization or using different classes of beam shapes [6,7].
A method for calculating the aperture averaging function of an arbitrary shape optical receiver by mapping it to a one-dimensional array
Published in Waves in Random and Complex Media, 2022
Both theoretically and experimentally, free-space optical communication has been studied for a long time [1]. Historically, there are two types of receiving telescopes most often used in free-space optical communication: the circular lens and the Cassegrain optical telescope. Hundreds of years ago, during the European Renaissance, hand-ground lenses were used to make telescopes. Galileo, Kepler, Scheiner, Huygens, and Newton all studied optical telescopes. At that time, the aperture of an optical telescope was very small, so it was appropriate to use a glass lens. With the increasing size of the optical aperture used, the optical aberration of different lens combinations is becoming more and more difficult to correct. Therefore, the Cassegrain optical telescopes and the Gregory optical telescopes appear. Their main optical surface is an aspherical mirror.
Anomalous beam spreading of Airy vortex beam arrays propagating in a moderate turbulent atmosphere
Published in Journal of Modern Optics, 2022
Xifu Yue, Yu Shang, Wenxuan Wang, Rui Zhao, Benyi Wang, Kezhen Han, Liping Zhang, Chengxin Lei, Zhongsheng Man, Xiaolu Ge
In this paper, the relative beam width is adopted to describe the BS caused by turbulent atmosphere. The effects of the transverse displacement parameter d and the topological charge m on the BSs of AVBA and AGVBA propagating in a moderate turbulent atmosphere are numerically studied and the differences between them are analysed and compared. With the increase of propagation distance or transverse displacement parameter d, the BSs of two vortex beam arrays become more and more seriously. Due to the Gaussian function truncation and optical vortex modulation, the anomalous BSs of AVBA and AGVBA with different transverse displacement parameter and topological charge in the turbulent atmosphere are shown. The results will provide helpful reference for selecting suitable parameters of AVBA as information carrier in free-space optical communication.