- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Scintillation experiments with non-uniformly and uniformly correlated spatially partially coherent laser beams propagating underwater
摘要： We report on experiments where non-uniformly correlated (NUC), Gaussian Schell (GSM) and Multi-Gaussian Schell (MGSM) model spatially partially coherent laser beams were propagated underwater. Two scenarios were explored: still water and mechanically agitated water. The main objective of our study was the experimental comparison of the scintillation performance among beams with different correlation functions. The results show generally increased absolute values of scintillation index for NUC beams as compared with GSM and MGSM beams. We hypothesized that this effect is related to the method of NUC beams generation. It should be noted, that the presented results document only the given experimental scenarios and show the relative comparison between GSM, MGSM and NUC beams with Gaussian used as a turbulence level benchmark. Further investigation is necessary to broaden the scope of our explorations of the propagation of uniformly correlated spatially partially coherent as well as non-uniformly correlated beam classes.
关键词： multi-Gaussian Schell model beam,Non-uniformly correlated,partial spatial coherence,scintillation,experimental validation,underwater laser propagation
更新于2025-09-12 10:27:22
-
Experimental study of the effects of thermally induced optical turbulence on underwater wireless optical communication link parameters
摘要： In this experimental research, the effects of refractive index fluctuations resulting from temperature fluctuations on some of the most important underwater communication link parameters such as the average received power, Signal to Noise Ratio (SNR) and normalized power variance (aperture averaged scintillation) has been experimentally investigated. Moreover, by introducing a new probability density function which is fitted more appropriately to the experimental data obtained from our simulator tank, the Bit Error Rate (BER) behavior of an Underwater Wireless Optical Communication (UWOC) link is also studied. These investigations are essential due to the optical turbulence limiting effects on the performance of UWOC systems. The experimental results indicate that reduction of the aperture averaged scintillation effects by using of optical components in the transmitter and receiver of UWOC links can enhance their performance. In general, increasing the strength of the optical turbulence (by increasing the temperature gradient induced by the rod heater) or the distance of the localized turbulence screen generated by temperature gradient from the transmitter plane, the aperture averaged scintillation decreases and consequently the SNR raises whilst the BER declines. Also, expanding the aperture diameter of the receiver optics reduces the normalized power variance which leads to decrease and increase in the BER and the SNR amounts respectively. The results are presented as experimental simulation graphs.
关键词： Laser beam propagation through turbulence,aperture averaged scintillation,Probability density function,BER,SNR,Underwater optical communication link
更新于2025-09-12 10:27:22
-
Tapping underwater wireless optical communication in pure water and natural Dead-Sea ultra-high-salinity water by diffraction grating
摘要： Although underwater wireless optical communication (UWOC) receives much interest lately, security issues associated with it get little attention. In this paper, we show how a message communicated using UWOC can be eavesdropped without a sender's or addressee's awareness, by employing a diffraction grating. We also analyze the propagation of multiple diffracted Gaussian beams in water, and show for the first time that UWOC is feasible even in natural ultra-salty water taken from the Dead-Sea. We evaluate how far from the addressee the message could be eavesdropped, and discuss different possibilities of tapping the channel – one from the air and one underwater.
关键词： diffraction grating,eavesdropping,underwater wireless optical communication,ultra-salty water,UWOC,Dead-Sea
更新于2025-09-12 10:27:22
-
[IEEE 2019 IEEE International Ultrasonics Symposium (IUS) - Glasgow, United Kingdom (2019.10.6-2019.10.9)] 2019 IEEE International Ultrasonics Symposium (IUS) - PMUT-Enabled Underwater Acoustic Source Localization System
摘要： The present work presents the novel application of Piezoelectric Micromachined Ultrasonic Transducer (PMUT) arrays in an Underwater Acoustic Source Localization System. Based on the difference in the time of arrival of ultrasonic bursts originating from an acoustic beacon, the system is capable of determining the direction to the source with no theoretical limitation on the angular range. A cross correlation technique is used to estimate the time of arrival difference between the received signals. Experiments are performed with the prototype submerged in liquid in a tank for arbitrary positions of a beacon, showing large potential for application of the system in a miniaturized, integrated platform for underwater source localization.
关键词： underwater,Direction of Arrival,PMUT,ultrasonic,AVS
更新于2025-09-12 10:27:22
-
Mineral carbonate dissolution with increasing CO2 pressure measured by underwater laser induced breakdown spectroscopy and its application in carbon sequestration
摘要： In this study, the ability of laser-induced breakdown spectroscopy (LIBS) to measure the in situ aqueous dissolution of various mineral carbonates with increasing CO2 pressure was examined. Dissolution experiments included four geologically common mineral carbonates (CaCO3, MgCO3, MnCO3, SrCO3) and the CO2 pressure ranged from ambient to 250 bar. The ensuing plasma emission was spectrally analyzed, and the intensities of Ca, Mg, Mn, and Sr emission lines were used to monitor the respective metal cations released to the aqueous solution. The strong emission lines of Ca (Ca II 393.36, Ca II 396.84, Ca I 422.67 nm), Mg (unresolved magnesium doublet: Mg I 383.230, Mg I 383.829 nm), Mn (unresolved manganese triplet: Mn I 403.076, Mn I 403.307, Mn I 403.449 nm), and Sr (Sr II 407.77, Sr II 421.55, Sr I 460.73 nm) were identified in the spectra. The amounts of metals released from their respective carbonates were estimated at different time intervals following the CO2 injection (5 m, 1, 2, 3, 4, 24 h) and at different pressures (50, 100, 150, 200, 250 bar) using calibration models developed at corresponding pressure settings. The results demonstrated that the pressure-induced dissolution of all carbonates was consistent with their expected and selective pH-dependent solubility. The dissolution rate of CaCO3, MgCO3, and SrCO3 was found to be higher than that of MnCO3. The dissolution of constituents in a Mt. Simon sandstone associated with a deep saline reservoir at elevated CO2 pressure was also studied and Ca release was quantified. The results demonstrated that real-time monitoring of carbonate dissolution by LIBS may provide a useful indirect detection system indicative of CO2 leakage from geologic carbon storage sites.
关键词： Monitoring of carbonate dissolution by LIBS,Underwater LIBS for CO2 leakage detection,Carbonate dissolution
更新于2025-09-12 10:27:22
-
Underwater Characterization and Monitoring of Amorphous and Monocrystalline Solar Cells in Diverse Water Settings
摘要： Most of Solar Photovoltaic (PV) cells are limited to space, dryland and rooftop applications leading to huge scope in exploring the performance of PV cells in an underwater environment. Such underwater Solar energy has tremendous potential to be used in many commercial and defense applications like sensors, underwater vehicles, autonomous power systems, etc. Nowadays, another major constraint in Solar PV systems is the cooling and cleaning of PV cells, which can also be overcome by placing PV cells underwater. Although the Solar spectrum itself changes underwater and becomes narrower with increasing the water depth, yet one of the possible solutions is using a suitable type of Solar cells for maximum power conversion underwater. In this work, an experimental setup has been designed and implemented to create an underwater environment. Further, Solar cells have been encapsulated with polydimethylsiloxane (PDMS) and diverse characterizations have been accomplished to sense the behavior of amorphous and monocrystalline cells with different water types. This study gives a better understanding to monitor the performance characteristics of Solar PV cells underwater with various factors such as the water depth, type of Solar cell, salinity, total dissolved salts and other impurities which will immensely affect the performance of Solar cells underwater.
关键词： Water-salinity,Monocrystalline solar cell,Underwater Solar power,PDMS (Polydimethylsiloxane),Photovoltaic (PV) technology,Amorphous solar cell
更新于2025-09-12 10:27:22
-
Microfluidic Channels Fabrication Based on Underwater Superpolymphobic Microgrooves Produced by Femtosecond Laser Direct Writing
摘要： A strategy is proposed here to fabricate microfluidic channels based on underwater superpolymphobic microgrooves with nanoscale rough surface structure on glass surface produced by femtosecond (fs) laser processing. The fs laser-induced micro/nanostructure on glass surface is able to repel liquid polydimethylsiloxane (PDMS) underwater, with the contact angle (CA) of 155.5 ± 2.5° and CA hysteresis of 2.7 ± 1.5° to a liquid PDMS droplet. Such phenomenon is defined as the underwater “superpolymphobicity”. Microchannels as well as microfluidic systems are easily prepared and formed between the underwater superpolymphobic microgrooves-textured glass substrate and the cured PDMS layer. Because the tracks of the laser scanning lines are programmable, arbitrary-shaped microchannels and complex microfluidic systems can be potentially designed and prepared through fs laser direct writing technology. The concept of “underwater superpolymphobicity” presented here offers us a new strategy for selectively avoiding the adhesion at the polymer/substrate interface and controlling the shape of cured polymers, none of these applications can find analogs in previously reported superwetting materials.
关键词： femtosecond laser,microfluidic channels,underwater superpolymphobicity,microfluidic systems,PDMS
更新于2025-09-12 10:27:22
-
Hearing the Sounds of Aquatic Life Using Optical Fiber Micro-tip based Hydrophone
摘要： For marine bioacoustics applications, the sounds by aquatic animals must be recorded with high precision and minimal noise in order to extract valuable information. For such marine applications, we propose and demonstrate an optical fiber micro-tip based hydrophone. The hydrophone design consists of an extrinsic Fabry-Perot interferometer which utilizes fiber micro-tip and processed aluminium foil as two partially reflecting mirrors. The packaged optical fiber hydrophone of dimensions 1.4 cm x 1.4 cm x 2 cm, with a microtip diameter of 31.23 μm and natural rubber diaphragm of 6 mm diameter shows a high sensitivity of 8.94 nm/mPa or -41.42 dB re 1 nm/μPa at 1 KHz. The hydrophone shows an excellent signal to noise ratio and the noise-limited minimum detectable pressure is as low as 0.388 μPa/√Hz at 1 KHz. The linear working range of the hydrophone is 0-3950 Hz. The experimental results show that the proposed optical fiber hydrophone can very accurately detect the click trains produced by dolphins for echolocation. Further, depending on the applications, the performance parameters of the proposed hydrophone can be tailored by changing the diaphragm thickness and diameter, thus opening a new platform to study marine environment.
关键词： Optical fibers,Acoustic signal detection,Underwater Optical equipment,Underwater acoustics,fiber sensors
更新于2025-09-11 14:15:04
-
[IEEE 2018 IEEE International Workshop on Metrology for the Sea; Learning to Measure Sea Health Parameters (MetroSea) - Bari, Italy (2018.10.8-2018.10.10)] 2018 IEEE International Workshop on Metrology for the Sea; Learning to Measure Sea Health Parameters (MetroSea) - Preliminary assessment of Photogrammetric Approach for detailed dimensional and colorimetric reconstruction of Corals in underwater environment
摘要： The use of 3D scan technologies to provide 3D color models of some bio-constructor organisms without removing them from the sea represents a valuable contribution for the preservation of current marine flora and fauna. The necessity to perform accurate measurements of volume, surface area and other morphometric characteristics is to increase the knowledge about the habitat-forming species. In this way, it is possible to describe the modification they made to the seabed topography, to monitor their shape modification according to local environmental conditions and evaluate 3D structure and color of some species sensitive to climate changes. The necessity of working in an environment characterized by different light conditions and particulate concentrations, the need of having high-performance sealing and, last but not least, the portability guarantee have limited the range of possible measurement techniques among those available for 3D shape reconstruction. Within this context, the idea underlying this research activity is to adopt photogrammetric technique for underwater surveys. In particular, a comprehensive and detailed analysis of a small object in and outside-water is performed in lab-scale tests by means of two different camera lenses, to pinpoint the effectiveness and the weakness of the solution identified. Another contribution of this paper is the uses of a color correction algorithm in order to correct the scene illumination, improving the 3D reconstruction of the detected objects. It is shown the capability of the algorithm to solve the color mismatch problem in multi-view color images. Results show the 3D models with details very well reconstructed both in and outside-water. The image pre-processing step drastically improve the matching points recognition and the reconstruction of the whole object independently to environmental illumination changes.
关键词： underwater 3D reconstruction,detailed scan,image processing,photogrammetry,color correction
更新于2025-09-11 14:15:04
-
Photon-Counting Underwater Wireless Optical Communication by Recovering Clock and Data From Discrete Single Photon Pulses
摘要： To realize a long-distance underwater communication by using low-cost light emitting diode (LED) and single photon avalanche diode (SPAD), we proposed a method for recovering clock and data directly from discrete random pulse sequences output by SPAD. On this basis, a new communication model is established, taking into account not only ?uctuations in photon ?ux and quantum ef?ciency of photon detection in a time-slot, but also the phase difference of the recovered clock caused by it. A photon-counting underwater optical wireless communication (UOWC) system was built. The effects of the system setting parameters such as the number of gating signals, synchronous character length and baud rate on the average bit error rate (BER) were veri?ed by experiments. The experimental results show that under condition of only average 10 photons in one time-slot, photon-counting UOWC with a BER of 3.51 × 10?4 and a baud rate of 1 Mbps can be achieved.
关键词： clock synchronization,Underwater optical wireless communication (UOWC),photon-counting,data recovery
更新于2025-09-11 14:15:04