Submarine optical fiber communication provides an unrealized deep-sea observation network(Springer Science and Business Media LLC, 2023-09-18) Guo, Yujian; Marin, Juan M.; Ashry, Islam; Trichili, Abderrahmen; Havlik, Michelle-Nicole; Ng, Tien Khee; Duarte, Carlos M.; Ooi, Boon S.; Red Sea Research Center and Computational Biosciences Research Center, King Abdullah University of Science and Technology, Thuwal, Saudi Arabia.; Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division; Marine Science Program; Red Sea Research Center (RSRC); Biological and Environmental Science and Engineering (BESE) Division; Electrical and Computer Engineering Program; Computational Bioscience Research Center (CBRC)
Oceans are crucial to human survival, providing natural resources and most of the global oxygen supply, and are responsible for a large portion of worldwide economic development. Although it is widely considered a silent world, the sea is filled with natural sounds generated by marine life and geological processes. Man-made underwater sounds, such as active sonars, maritime traffic, and offshore oil and mineral exploration, have significantly affected underwater soundscapes and species. In this work, we report on a joint optical fiber-based communication and sensing technology aiming to reduce noise pollution in the sea while providing connectivity simultaneously with a variety of underwater applications. The designed multifunctional fiber-based system enables two-way data transfer, monitoring marine life and ship movement near the deployed fiber at the sea bottom and sensing temperature. The deployed fiber is equally harnessed to transfer energy that the internet of underwater things (IoUTs) devices can harvest. The reported approach significantly reduces the costs and effects of monitoring marine ecosystems while ensuring data transfer and ocean monitoring applications and providing continuous power for submerged IoUT devices.
Multifunctional difluoroboron β-diketonate-based luminescent receiver for a high-speed underwater wireless optical communication system(Optica Publishing Group, 2023-09-14) Wang, Yue; Wang, Jian-Xin; Alkhazragi, Omar; Gutierrez Arzaluz, Luis; Zhang, Huafan; Kang, Chun Hong; Ng, Tien Khee; Bakr, Osman; Mohammed, Omar F.; Ooi, Boon S.; Electrical and Computer Engineering Program; Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division; Physical Science and Engineering (PSE) Division; Material Science and Engineering Program; KAUST Catalysis Center (KCC); Chemical Science Program; Advanced Membranes and Porous Materials Research Center
The last decade has witnessed considerable progress in underwater wireless optical communication in complex environments, particularly in exploring the deep sea. However, it is difficult to maintain a precise point-to-point reception at all times due to severe turbulence in actual situations. To facilitate efficient data transmission, the color-conversion technique offers a paradigm shift in large-area and omnidirectional light detection, which can effectively alleviate the étendue limit by decoupling the field of view and optical gain. In this work, we investigated a series of difluoroboron β-diketonate fluorophores by measuring their photophysical properties and optical wireless communication performances. The emission colors were tuned from blue to green, and >0.5 Gb/s data transmission was achieved with individual color channel in free space by implementing an orthogonal frequency-division multiplexing (OFDM) modulation scheme. In the underwater experiment, the fluorophore with the highest transmission speed was fabricated into a 4×4 cm2 luminescent concentrator, with the concentrated emission from the edges coupled with an optical fiber array, for large-area photodetection and optical beam tracking. The net data rates of 130 Mb/s and 217 Mb/s were achieved based on nonreturn- to-zero on-off keying and OFDM modulation schemes, respectively. Further, the same device was used to demonstrate the linear light beam tracking function with high accuracy, which is beneficial for sustaining a reliable and stable connection in a dynamic, turbulent underwater environment.
Acousto-optic Cooperative Pointing, Acquisition and Tracking Method for Undersea Laser Communication(IEEE, 2023-06-05) Weng, Yang; Chun, Sehwa; Sekimori, Yuki; Alkhazragi, Omar; Matsuda, Takumi; Trichili, Abderrahmen; Ng, Tien Khee; Ooi, Boon S.; Maki, Toshihiro; Electrical and Computer Engineering Program; Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division; The University of Tokyo,Institute of Industrial Science,Tokyo,Japan; Meiji University,School of Science and Technology,Kanagawa,Japan
Underwater laser communication has shown good performance in terms of rate, bandwidth and delay, and is a promising communication method for establishing internet of underwater things. In the past, all-optical pointing, acquisition and tracking (PAT) methods were used to establish laser links between underwater platforms. We propose a combined acousto-optical PAT method for link establishment in underwater laser communication to reduce the time consumed in the acquisition process and thus improve efficiency. The proposed method was tested and analyzed in the designed environment.
Chaotic-cavity surface-emitting lasers for optical wireless communication and low-speckle illumination(AIP Publishing, 2023-08-14) Alkhazragi, Omar; Dong, Ming; Chen, Liang; Kong, Meiwei; Melinte, Georgian; Liang, Dong; Ng, Tien Khee; Zhang, Junping; Bagci, Hakan; Ooi, Boon S.; King Abdullah University of Science and Technology (KAUST); Photonics Laboratory, Division of Computer, Electrical, and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST) 1 , Thuwal 23955-6900, Saudi Arabia; Electrical and Computer Engineering (ECE) Program, Division of Computer, Electrical, and Mathematical Sciences and Engineering, King Abdullah University of Science and Technology (KAUST) 2 , Thuwal 23955-6900, Saudi Arabia; KAUST Core Labs, King Abdullah University of Science and Technology (KAUST) 3 , Thuwal 23955-6900, Saudi Arabia; Electrical and Computer Engineering Program; Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division; Biological and Environmental Science and Engineering (BESE) Division; Electron Microscopy; Huawei Technologies Co., Ltd. 4 , Shenzhen 518129, China
Though necessary and advantageous in many fields, the high coherence of lasers is detrimental to their performance in certain applications, including illumination, imaging, and projection. This is due to the formation of coherence artifacts, commonly known as speckles, resulting from the interference of randomly scattering spatially coherent photons. It is possible to resolve this issue by increasing the number of mutually incoherent modes emitted from the laser. In vertical-cavity surface-emitting lasers (VCSELs), this can be performed by designing them to have chaotic cavities. This paves the way toward their use in simultaneous illumination and communication scenarios. Herein, we show that chaotic-cavity broad-area VCSELs can achieve significantly broader modulation bandwidths (up to 5 GHz) and higher data rates (up to 12.6 GB/s) compared to other low-coherence light sources, with a lower speckle contrast. We further report a novel technique for lowering the speckle contrast by carefully designing the AC signal used for communication. We show that the apparent spatial coherence is dramatically decreased by inserting a short chirp signal between symbols. Using this method with a chaotic-cavity VCSEL, the number of apparent modes can be up to 450, compared to 88 modes measured from a conventional broad-area VCSEL (a fivefold increase). In light of the recent advances in visible-light VCSELs, this work shows the potential of low-coherence surface-emitting lasers (LCSELs) in simultaneous illumination and optical wireless communication systems since they combine the high speed of lasers with the excellent illumination properties of light-emitting diodes.
Beam wander prediction with recurrent neural networks(Optica Publishing Group, 2023-08-14) Briantcev, Dmitrii; Cox, Mitchell; Trichili, Abderrahmen; Ooi, Boon S.; Alouini, Mohamed-Slim; Computer, Electrical and Mathematical Sciences Division at King Abdullah University of Science and Technology (KAUST), Thuwal, Makkah Province, Saudi Arabia; Electrical and Computer Engineering Program; Computer, Electrical and Mathematical Science and Engineering (CEMSE) Division; School of Electrical and Information Engineering, University of the Witwatersrand, Johannesburg, South Africa
Among the problems that prevent free-space optical communication systems from becoming a truly mainstream technology is beam wander, which is especially important for structured light beams since beam misalignment introduces additional crosstalk at the receiver. The paper suggests a recurrent neural network-based (RNN) solution to predict beam wander in free space optics (FSO). The approach uses past beam center of mass positions to predict future movement, significantly outperforming various prediction types. The proposed approach is demonstrated using under-sampled experimental data over a 260 m link as a worst-case and over-sampled simulated data as a best-case scenario. In addition to conventional Gaussian beams, Hermite- and Laguerre-Gaussian beam wander is also investigated. With a 20 to 40% improvement in error over naive and linear predictions, while predicting multiple samples ahead in typical situations and overall matching or outperforming considered predictions across all studied scenarios, this method could help mitigate turbulence-induced fading and has potential applications in intelligent re-transmits, quality of service, optimized error correction, maximum likelihood-type algorithms, and predictive adaptive optics.