- 标题
- 摘要
- 关键词
- 实验方案
- 产品
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[IEEE 2019 IEEE 2nd British and Irish Conference on Optics and Photonics (BICOP) - London, United Kingdom (2019.12.11-2019.12.13)] 2019 IEEE 2nd British and Irish Conference on Optics and Photonics (BICOP) - Temperature Stability of Elastomeric Colloidal Quantum Dot Colour Converter
摘要： Underwater wireless optical communications are an emerging solution to the expanding demand for broadband links in oceans and seas. In this paper, a cellular underwater wireless optical code division multiple-access network is proposed to provide broadband links for commercial and military applications. The optical orthogonal codes are employed as signature codes of underwater mobile users. Fundamental key aspects of the network, such as its backhaul architecture, its potential applications, and its design challenges, are presented. In particular, a promising underwater localization and positioning scheme based on this cellular network is presented. Furthermore, the proposed network is used as infrastructure of centralized, decentralized and relay-assisted underwater sensor networks for high-speed real-time monitoring. Finally, probable design challenges, such as cell edge coverage, blockage avoidance, power control, and network capacity, are addressed.
关键词： power control,optical CDMA networks,undersea localization and positioning,underwater sensor networks,Underwater wireless optical communications,relay-assisted transmission
更新于2025-09-19 17:13:59
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[IEEE 2019 International Conference on Recent Advances in Energy-efficient Computing and Communication (ICRAECC) - Nagercoil, India (2019.3.7-2019.3.8)] 2019 International Conference on Recent Advances in Energy-efficient Computing and Communication (ICRAECC) - Free Space Optical Communication and Laser Beam Propagation through Turbulent Atmosphere: A Brief Survey
摘要： A particle ?lter (PF)-based robust navigation with fault diagnosis (FD) is designed for an underwater robot, where 10 failure modes of sensors and thrusters are considered. The nominal underwater robot and its anomaly are described by a switching-mode hidden Markov model. By extensively running a PF on the model, the FD and robust navigation are achieved. Closed-loop full-scale experimental results show that the proposed method is robust, can diagnose faults effectively, and can provide good state estimation even in cases where multiple faults occur. Comparing with other methods, the proposed method can diagnose all faults within a single structure, diagnose simultaneous faults, and it is easily implemented.
关键词： fault tolerance,Fault diagnosis (FD),switch-mode hidden Markov model (HMM),remotely operated underwater vehicle (ROV),particle ?lter (PF),underwater navigation
更新于2025-09-19 17:13:59
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Clock and Data Recovery-Free Data Communications Enabled by Multi-core Fiber with Low Thermal Sensitivity of Skew
摘要： Underwater wireless optical communications are an emerging solution to the expanding demand for broadband links in oceans and seas. In this paper, a cellular underwater wireless optical code division multiple-access network is proposed to provide broadband links for commercial and military applications. The optical orthogonal codes are employed as signature codes of underwater mobile users. Fundamental key aspects of the network, such as its backhaul architecture, its potential applications, and its design challenges, are presented. In particular, a promising underwater localization and positioning scheme based on this cellular network is presented. Furthermore, the proposed network is used as infrastructure of centralized, decentralized and relay-assisted underwater sensor networks for high-speed real-time monitoring. Finally, probable design challenges, such as cell edge coverage, blockage avoidance, power control, and network capacity, are addressed.
关键词： power control,relay-assisted transmission,Underwater wireless optical communications,undersea localization and positioning,underwater sensor networks,optical CDMA networks
更新于2025-09-19 17:13:59
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Historical perspective of free space optical communications: from the early dates to today's developments
摘要： This survey article discusses the revolutions of wireless communication technologies right from the prehistoric man's fire signals to today's space optical communications. A brief description of evaluations of communication technologies from the ancient Greece to today's mature telecommunication fields is discussed in this review paper. Principle, significance, demonstration and development of free space optical (FSO) communication technology over different decades are discussed. Major FSO channel limitations, temporal and spatial challenges of FSO communication system and their state-of-art mitigation techniques are presented. Classical quantitative analysis of reliability of FSO communication, developments on radio over FSO (RoFSO) and hybrid FSO/RF systems are also explained. Advanced developments of FSO communication techniques such as optical free space wavelength division multiplexing (WDM), sub-carrier multiplexing (SCM), worldwide interoperability for microwave access (WiMAX), visible light communications (VLC) and vehicular visible light communications (VVLC) are reported. Deep space optical communication systems and next generation FSO wireless terrestrial/global network architecture are summarised. Research challenges of FSO systems for internet of things/everything (IoT/IoE), 5G communication, mobile-network, terahertz spectrum, quantum communication and underwater optical applications are presented. Based on the review, we outlined the challenges that need to be addressed in near-future researches to realize full potential FSO communication systems.
关键词： quantum communication,RoFSO,SCM,FSO,IoT/IoE,5G,WDM,underwater optical applications,VVLC,free space optical communications,VLC,WiMAX
更新于2025-09-19 17:13:59
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Design of a Multi-wavelength Fiber Laser Based on Tm:Er:Yb:Ho Co-doped Germanate Glass
摘要： Time reversal (TR) exploits spatial diversity to achieve spatial and temporal focusing in complex environments. Over the last decade, the TR concept has been applied successfully to phase-coherent acoustic communications in time-varying multipath ocean environments, as an alternative to conventional adaptive multichannel equalization. Temporal focusing (pulse compression) mitigates the intersymbol interference (ISI) and subsequent single-channel equalization removes the residual ISI, thus providing nearly optimal performance in theory. The spatial focusing capability facilitates multiuser or multiple-input–multiple-output (MIMO) communications without explicit use of time, frequency, or code division multiplexing, while an adaptive TR approach can reduce further the crosstalk among users or multiple transmitters. TR communications can be extended easily to time-varying channels using a block-based approach with channel updates. This paper provides an overview of TR communications in both shallow and deep water and recent advances including bidirectional equalization, multiuser communications with mobile users, and communication with a glider serving as a mobile gateway.
关键词： crosstalk,underwater acoustic (UWA) communication,Adaptive multichannel equalization,time reversal (TR),MIMO/multiuser communication
更新于2025-09-19 17:13:59
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[IEEE 2019 2nd International Conference on Intelligent Computing, Instrumentation and Control Technologies (ICICICT) - Kannur,Kerala, India (2019.7.5-2019.7.6)] 2019 2nd International Conference on Intelligent Computing, Instrumentation and Control Technologies (ICICICT) - Calibration of an optical sensor for in vivo blood glucose maeasurenaent
摘要： Underwater acoustic (UWA) channels are characterized by a severe spread in time and frequency, and are usually labeled as “doubly spread channels.” In this paper, we propose Doppler-resilient orthogonal signal-division multiplexing (D–OSDM), to provide a highly reliable communication environment in doubly spread channels for UWA communication. D–OSDM multiplexes several data vectors in addition to a pilot vector, and preserves orthogonality among them even after propagation through doubly spread channels, under the assumption that the channel can be modeled by a basis expansion model (BEM). We describe the signal processing steps at the transmitter and the receiver for D–OSDM, and evaluate its performance by both simulations and experiments. To generate a doubly spread channel, a test tank with a wave generator is employed. The obtained results suggest that D–OSDM can provide low-power and high-quality UWA communications in channels with large delay and Doppler spreads; for example, D–OSDM succeeds to achieve a block error rate (BLER) of 10 while BEM-based orthogonal frequency-division multiplexing (OFDM) has a BLER ?oor of in the experiments. Equivalently, D–OSDM can reduce the 10 signal power required for communications to achieve the same BER signi?cantly. Overall, it was found that D–OSDM can become a powerful communication tool for underwater operations.
关键词： multipath channels,Doppler,underwater acoustic (UWA) communication
更新于2025-09-19 17:13:59
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Investigation of 3 dB Optical Intensity Spot Radius of Laser Beam under Scattering Underwater Channel
摘要： An important step in the design of receiver aperture and optimal spacing of the diversity scheme for an underwater laser communication system is to accurately characterize the two-dimensional (2D) spatial distribution of laser beam intensity. In this paper, the 2D optical intensity distribution and 3 dB optical intensity spot radius (OISR) are investigated due to the dominating optical intensity of laser beam being within the 3 dB OISR. By utilizing the Henyey–Greenstein function to compute the scattering angles of photons, the effects of the scattering underwater optical channel and optical system parameters on 3 dB OISR are examined based on the Monte Carlo simulation method. We have shown for the ?rst time that in the channel with a high density of scattering particles, the divergence angle of the laser source plays a negligible role in 3 dB OISR. This is an interesting phenomenon and important for optical communication as this clearly shows that the geometric loss is no longer important for the design of receiver aperture and optimal spacing of the diversity scheme for the underwater laser communication system in the highly scattering channel.
关键词： 3 dB optical intensity spot radius,scattering underwater channel,Monte Carlo simulation method
更新于2025-09-19 17:13:59
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Heterostructured PPy/ZnO layer assembled PAN nanofibrous membrane with robust visible-light-induced self-cleaning for high efficient water purification with fast separation flux
摘要： Developing superhydrophilic/underwater superoleophobic surface to restrict oil pollution from oil/water separation process has been an effective method. However, inevitable adsorption and aggregation of organic contaminants onto membrane surface from complex oily sewage usually caused irreversibly decrease of flux, injurie of anti-oilfouling and shorten lifespan for separation membrane. Thus, a neoteric antifouling and renewable membrane is high desired. Herein, based on stabilized PAN nanofibers and followed assembled heterostructured PPy/ZnO layer with hierarchical structures onto the nanofibers surface, we reported a robust visible-light-induced self-repairable oil/water separation membrane. The SPAN-PPy/ZnO membrane displays superhydrophilicity (≈0°) and underwater superoleophobicity (>150°) for different oils, robust mechanical strength (≈408 MPa of Young’s modulus) and underwater high oil intrusion pressure (>120 kPa). Importantly, the as-prepared membrane not exhibits ultrafast permeation flux and high separation efficiency for oil/dyes/water emulsion, but also displays robust recovery ability (96%) after organic-polluted after 20 min light irradiation. We anticipate this composite membrane with outstanding separation capablity and robust flux recovery capable can provide a novel method for treation the large volume of wastewater purification.
关键词： heterostructured PPy/ZnO,visible-light-induced self-cleaning,superhydrophilic,underwater superoleophobic,oil/water separation
更新于2025-09-19 17:13:59
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[IEEE 2019 1st International Conference on Electrical, Control and Instrumentation Engineering (ICECIE) - Kuala Lumpur, Malaysia (2019.11.25-2019.11.25)] 2019 1st International Conference on Electrical, Control and Instrumentation Engineering (ICECIE) - Development of RGB LED Based Compact Multipurpose Colorimeter for Hemoglobin Estimation of Blood
摘要： Time reversal (TR) exploits spatial diversity to achieve spatial and temporal focusing in complex environments. Over the last decade, the TR concept has been applied successfully to phase-coherent acoustic communications in time-varying multipath ocean environments, as an alternative to conventional adaptive multichannel equalization. Temporal focusing (pulse compression) mitigates the intersymbol interference (ISI) and subsequent single-channel equalization removes the residual ISI, thus providing nearly optimal performance in theory. The spatial focusing capability facilitates multiuser or multiple-input–multiple-output (MIMO) communications without explicit use of time, frequency, or code division multiplexing, while an adaptive TR approach can reduce further the crosstalk among users or multiple transmitters. TR communications can be extended easily to time-varying channels using a block-based approach with channel updates. This paper provides an overview of TR communications in both shallow and deep water and recent advances including bidirectional equalization, multiuser communications with mobile users, and communication with a glider serving as a mobile gateway.
关键词： time reversal (TR),underwater acoustic (UWA) communication,Adaptive multichannel equalization,MIMO/multiuser communication,crosstalk
更新于2025-09-19 17:13:59
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Underwater laser micro-milling of fine-grained aluminium and the process modelling by machine learning
摘要： Nanosecond-pulsed laser ablation is often accompanied by adverse thermal effects such as oxidation, debris recast and burr formation. To reduce these effects, in this paper, the authors present the underwater laser milling process using RSA-905 fine-grained aluminium as the target material for the first time. The results show that channels up to 200 μm in width, 700 μm depth and bottom roughness around 1 μm Ra could be fabricated with reduced thermal effects. By conducting multi- and single-factor experiments, empirical models relating the laser processing parameters to the key dimensions of channels were derived using artificial neural network (ANN) algorithm and polynomial regression (PR), and the models’ accuracies were evaluated. Based on the models, the cross-section profile of a channel subject to a given set of processing parameters can be predicted. The process can serve as a pre-treatment technique of mechanical milling such that the tool life will be extended and the profile of a desired feature can be precisely defined.
关键词： Regression analysis,Channel fabrication,Machine learning,Underwater laser machining,Burr-free
更新于2025-09-19 17:13:59