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[IEEE 2019 IEEE International Conference on Signal Processing, Communications and Computing (ICSPCC) - Dalian, China (2019.9.20-2019.9.22)] 2019 IEEE International Conference on Signal Processing, Communications and Computing (ICSPCC) - Enabling technologies for high-speed LED based underwater visible light communications
摘要： Underwater optical wireless communication (UWOC) is an interesting area need to be explored. In recent years, underwater visible light communication (UVLC) is expected to act as an alternative candidate in next-generation underwater wireless optical communications for the Internet of Underwater Things. The challenge is that the absorption, scattering, diffraction effect and turbulence of water medium, which can bring large attenuation and nonlinearity penalty. Therefore, it needs to apply lots of advanced modulation formats which including orthogonal frequency division multiplexing (OFDM), discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S OFDM) and carrier-less amplitude and phase modulation (CAP) in UVLC signal system. What’s more, advanced digital processing algorithm such as pre/post equalization, nonlinear compensation and other algorithms based on artificial intelligence are needed. In this paper, we introduce three advanced modulation formats including DFT-S OFDM, OFDM and CAP employing probabilistic shaping for high-speed LED based underwater visible light communication.
关键词： underwater visible light communication,probabilistic shaping,advanced modulation formats
更新于2025-09-16 10:30:52
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Micro-channel fabrication on NiTi shape memory alloy substrate using Nd <sup>3+</sup> : YAG laser
摘要： Microchannel has been fabricated on NiTi shape memory alloy (SMA) sheet employing nanosecond Nd3+: YAG laser in open-air and underwater processing conditions. Microchannels were fabricated using three different laser wavelengths (1064, 532 and 355 nm) and scanning speeds (4, 10, 14 μm/s). A comparison of the effect of processing condition (open-air and underwater) and scanning speed on the kerf dimension has been examined. The scanning electron micrographs revealed no debris formation and no recast layer formation in underwater conditions whereas the surface irregularities were predominant in the open-air environment. Further, the influence of machining on NiTi in open-air and underwater was studied using UV-Vis spectroscopy. The austenitic phase attributed to shape memory characteristics was evident in processed material in comparison to unmachined material using the X-ray diffraction technique. In addition, differential scanning calorimetry demonstrated the phase transformation temperatures. The samples processed in open-air and underwater environment showed a significant shift in phase transformation temperatures. These laser-based processing techniques are highly useful in preserving smart material characteristics and fabrication of microchannels used in controlled volume drug delivery, microfluidic and waste or body heat-based actuated devices.
关键词： underwater,Nd3+: YAG,UV,NiTi,SMA,micro channeling,transformations,Laser
更新于2025-09-16 10:30:52
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Experimental and Theoretical Evidences of Hysteresis in Passive Mode-Locked Quantum Dots Lasers
摘要： In this paper, closed-form expressions for the performance of the normalized matched ?lter (NMF) detector are developed speci?cally for the case of large time-bandwidth product, N . As a test case, the task of detecting underwater acoustic signals is considered. While the matched ?lter is the most common detector used, the NMF detector is used in cases where the ambient noise is fast time varying and is hard to estimate. While the performance of the NMF has been studied, no closed-form expressions are given for the detection and false alarm probabilities, and the accuracy of the available approximations greatly deteriorates with N . As a result, evaluating the detection threshold from the receiver operating characteristic requires signi?cant, and sometimes untraceable, numerical calculations. This is speci?cally important for underwater acoustic signals, where due to the low signal-to-noise ratio, N is very large. The analysis performed in this paper solves this problem. The analysis is based on the probability distribution of the NMF to give an exact closed-form (tabulized) expression for the false alarm probability, and a relatively accurate approximation for the probability of detection, both for the large N case. These approximations are found accurate in numerical simulations. Results from an experiment conducted in the Mediterranean sea at the depth of roughly 1000 m validate the analysis.
关键词： receiver operating characteristic,matched ?lter,detection probability,detection,Underwater acoustics,false alarm probability
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE International Conference on Image Processing (ICIP) - Taipei, Taiwan (2019.9.22-2019.9.25)] 2019 IEEE International Conference on Image Processing (ICIP) - Learning Lightweight Pedestrian Detector with Hierarchical Knowledge Distillation
摘要： In order to transfer 3000-MW capacity of electricity from the mine-mouth coal-fired power plants in South Sumatra to the load center in Java, PLN Indonesia intends to build the Java-Sumatra Power Interconnection System. The scopes of these works of the Power Interconnection System are including: high voltage alternating current (HVAC) 500 kV Transmission Line in Java, HVAC 500 kV Transmission Line in Sumatra, high voltage direct current (HVDC) 500 kV Transmission Line in Java, HVDC 500 kV Transmission Line in Sumatra, and HVDC 500 kV Java-Sumatra submarine cables. This paper will analyze the financial feasibility study to ensure whether the project has economic benefit, and the asset would be used effectively and efficiently along its benefit period using life cycle cost analysis (LCCA). In this paper, an LCCA will be simulated to analyze three alternatives and to decide which alternative is the most profitable. Monte Carlo simulations and a break-even chart for a period of 30 years' operation of the interconnection system are part of the LCCA models to achieve the objectives of this paper.
关键词： cost benefit analysis,underwater,decision making,Risk analysis,project engineering,power transmission,availability,maintenance,cables,reliability
更新于2025-09-16 10:30:52
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166 Gbps data rate for underwater wireless optical transmission with single laser diode achieved with discrete multi-tone and post nonlinear equalization
摘要： In this paper, we experimentally demonstrate a 450-nm laser underwater wireless optical transmission system by using adaptive bit-power loading discrete multi-tone (DMT) and Volterra series based post nonlinear equalization. Post nonlinear equalization mitigates the nonlinear impairment of the UWOC system. By incorporating post nonlinear equalization with a 3rd-order diagonal plane kernel, the received signal-to-noise ratio (SNR) can be improved by ~2 dB compared with a linear equalization method. The measured transmission capacity of the UWOC system is 16.6 Gbps over 5 m, 13.2 Gbps over 35 m, and 6.6 Gbps over 55 m tap water channel, with bit error rates (BERs) below the standard hard-decision forward error correction (HD-FEC) limit of 3.8 × 10?3. The used electrical signal bandwidth is 2.75 GHz, corresponding to electrical spectrum efficiency of ～6 bit/s/Hz. The distance-datarate product reaches 462 Gbps*m at 35 m tap water transmission. To the best of our knowledge, both the data rate and distance-data rate product are the largest reported for single laser diode.
关键词： Volterra series,discrete multi-tone,underwater wireless optical communication,high-speed transmission,post nonlinear equalization
更新于2025-09-16 10:30:52
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Underwater performance of thin-film photovoltaic module immersed in shallow and deep waters along with possible applications
摘要： This article presents the experimental results of the underwater performance of amorphous silicon (a-Si) thin-film photovoltaic (TFPV) module. Electrical performance characteristics (current, voltage, power input, power output, and power conversion efficiency) of a-Si TFPV are evaluated considering the two installation conditions of Submerged Photovoltaics (SPV): shallow and deep waters. Experimental results showed that the a-Si TFPV could convert sun energy into electricity even in underwater environments. It is observed that there is a little drop in power outputs in deep waters than to shallow waters due to the variation in incident sunlight on to the photovoltaic (PV) module. Based on the outcome, few possible applications for underwater PV system are explored. The article is concluded by highlighting few critical points for future research.
关键词： Photovoltaics,thin films,underwater PV applications,underwater photovoltaics,underwater PV performance,sub-merged PV,PV in deep waters,floating photovoltaics,power conversion efficiency,PV cells
更新于2025-09-12 10:27:22
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Femtosecond Laser-Produced Underwater “Superpolymphobic” Nanorippled Surfaces: Repelling Liquid Polymers in Water for Applications of Controlling Polymer Shape and Adhesion
摘要： A femtosecond (fs) laser-ablated surface that repels liquid polymer in water is reported in this paper. We define this phenomenon as the “superpolymphobicity”. Three-level microstructures (including microgrooves, micromountains/microholes between the microgrooves, and nanoripples on the whole surface) were directly created on the stainless steel surface via fs laser ablation. A liquid polydimethylsiloxane (PDMS) droplet on the textured surface had the contact angle of 156 ± 3° and contact angle hysteresis less than 4° in water, indicating excellent underwater superpolymphobicity of the fs laser-induced hierarchical microstructures. The contact between the resultant superhydrophilic hierarchical microstructures and the submerged liquid PDMS droplet is verified at the underwater Cassie state. The underwater superpolymphobicity enables to design the shape of cured PDMS and selectively avoid the adhesion at the PDMS/substrate interface, different from the previously reported superwettabilities. As the examples, microlens array and microfluidics system were prepared based on the laser-induced underwater superpolymphobic microstructures.
关键词： superhydrophilicity,polymer repellence,three-level microstructure,femtosecond laser,underwater superpolymphobicity
更新于2025-09-12 10:27:22
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[IEEE OCEANS 2019 - Marseille - Marseille, France (2019.6.17-2019.6.20)] OCEANS 2019 - Marseille - Multi-laser Transmissometer for Ocean Optical Classification and Biofouling Detection
摘要： This research and development effort designs and tests new multi-laser transmissometer algorithms and hardware for ocean optical classification and autonomous biofouling detection. The system expands the collection of inherent optical properties and enables in-situ wavelength optimization for future optical communication links. Undersea testing succeeded and was contingent on several accomplishments, including developing robust algorithms, integrating opto-electronics within a custom chassis, and engineering a handheld-sized pressure vessel suitable for diverse field experimentation. The project verifies the feasibility of key enablers—autonomy, environmental classification, biofouling detection, and laser propagation—for remote undersea platforms with low size, weight, and power.
关键词： sensing,propagation,lasers,autonomy,underwater,undersea,oceanography,optimization,free space optical communication
更新于2025-09-12 10:27:22
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Gb/s underwater wireless optical communications using series-connected GaN micro-LED arrays
摘要： High speed wireless communications are highly desirable for many industrial and scientific underwater applications. Acoustic communications suffer from high latency and limited data rates, while Radio Frequency communications are severely limited by attenuation in seawater. Optical communications are a promising alternative, offering high transmission rates (up to Gb/s), while water has relatively low attenuation at visible wavelengths. Here we demonstrate the use of series-connected micro-light-emitting-diode (μLED) arrays consisting of 6 μLED pixels either 60 μm or 80 μm in diameter and operating at 450 nm. These devices increase the output power whilst maintaining relatively high modulation bandwidth. Using orthogonal frequency division multiplexing (OFDM) we demonstrate underwater wireless data transmission at rates of up to 4.92 Gb/s, 3.22 Gb/s and 3.4 Gb/s over 1.5 m, 3 m and 4.5 m, respectively, with corresponding bit error ratios (BERs) of 1.5×10-3, 1.1×10-3 and 3.1×10-3, through clear tap water, and Mb/s rates through >5 attenuation lengths (ALs) in turbid waters.
关键词： Underwater wireless optical communications,GaN,micro-light-emitting-diode arrays,turbid waters
更新于2025-09-12 10:27:22
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Physical implementation of underwater optical wireless system using spatial mode laser sources with optimization of spatial matching components
摘要： This article numerically investigates the e?ect of absorption and scattering loss in the presence of underwater. Presenting optical wireless channel, system is considered for fundamental mode (LP01) and its higher order modes (LP11, LP21 & LP31). The system performance is examined in terms of bit error rate (BER) with the function of wavelength, distance, attenuation and beam divergence. This implementation also shows the optimized results with respect to spatial mode matching component using spatial aperture and collimating lens as well. The graded results producing the new sight and will have greater attention among the optical wireless technology. The overall analysis of system design promises for better performance even at the treaty of high attenuation loss 49.34 dB/m on the propagation of all spatial modes. Each results obtained in this paper reaches the stability at the greater attenuation with the wavelength range from 1000 nm to 1600 nm.
关键词： Absorption,Attenuation,Underwater,BER,Scattering loss
更新于2025-09-12 10:27:22