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Underwater turbulence presents a myriad of challenges for underwater optical systems through wavefront distortion and beam deflection. In this work, an underwater turbulence emulator is developed and thoroughly characterized to experimentally test the proposed underwater turbulence mitigation technique. This technique applies a modified HOBBIT system introduced in atmospheric turbulence to the relatively unknown underwater turbulence domain. By varying a beam's spatial position and relative phase gradient, a volume of turbulence is rapidly probed to determine the beam state for optimal propagation. This probe and control method is applied in multiple facets, including improved optical power transmission as well as supporting a 25-Gbps communication link through a dynamic environment.
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http://dx.doi.org/10.1364/OE.499467 | DOI Listing |
Bioinspir Biomim
September 2025
Mechanical Engineering, University of California Berkeley, 6177 Etcheverry Hall, Berkeley, California, 94720, UNITED STATES.
Riblets inspired by natural shark skin denticles are widely recognized for their drag-reducing performance. Although previous research has predominantly focused on two-dimensional riblet geometries, three-dimensional topographies remain underexplored due to the complex architecture of denticle-inspired surfaces. Natural riblet arrays, comprising thousands of interconnected denticles, pose challenges in terms of parameterization, simulation, and fabrication.
View Article and Find Full Text PDFBiomimetics (Basel)
August 2025
The Laboratory of Cognitive and Decision Intelligence for Complex System, Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China.
Fault-tolerant control for bionic robotic fish presents significant challenges due to the complex dynamics and asymmetric propulsion introduced by joint failures. To address this issue, this paper proposes a fault-tolerant following control framework for multi-joint bionic robotic fish by combining fuzzy control methodologies and dynamic model correction. Firstly, offline fault analysis is conducted based on the dynamic model under multi-variable parameter conditions, quantitatively deriving influence factor functions that characterize the effects of different joint faults on velocity and yaw performance of the robotic fish.
View Article and Find Full Text PDFOff-axis Bessel-Gauss (BG) beams are used as a generation basis within an optical system that rapidly probes an underwater turbulent environment. Due to the rapidity of the scan, implemented using a modified Higher Order Bessel Beams Integrated with Time (HOBBIT) system, instantaneous realizations of the turbulence can be probed allowing optimal transmission paths in which the beams propagate, with minimal perturbations, through the complex turbulent environment. The results show a marked reduction in the effects of the turbulence, including over a 91% decrease in scintillation index, experienced by the beams propagated through these paths when compared to a centered on-axis BG beam.
View Article and Find Full Text PDFTo establish a secure and high-bandwidth communication link between the gateway node and the central node in the internet of underwater things (IoUwT), it is meaningful to introduce quantum key distribution (QKD) protocols into underwater wireless optical communication (UWOC) systems. However, the line-of-sight (LOS) requirement for photon transmission will pose an inevitable challenge to the QKD-based UWOC system. In this work, an optical intelligent reflecting surface (OIRS) array mounted on an autonomous underwater vehicle (AUV) is utilized for the first time to alleviate the LOS blockage and enable more reliable underwater wireless optical quantum link for both discrete-variable quantum key distribution (DV-QKD) and continuous-variable quantum key distribution (CV-QKD).
View Article and Find Full Text PDFIn this paper, we investigate the outage probability performance of underwater wireless optical communication for a vertical link. Due to temperature and salinity variations, turbulence in the vertical link ranges from strong to weak. The vertical link turbulence is modeled using a cascade of the gamma-gamma and hyperbolic tangent log-normal distributions.
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