Current Issue : July-September Volume : 2025 Issue Number : 3 Articles : 5 Articles
Optical fiber radioluminescence (RL) dosimetry has gained prominence in modern radiation therapy, offering real-time measurement and high spatial resolution. Our research group has developed a system utilizing a polymethyl methacrylate (PMMA) transmission fiber coupled with a photodetector and various scintillators, including doped silica fibers. A critical challenge in RL dosimetry lies in distinguishing the stem signal, generated by the transmission optical fiber, from the primary light signal produced by the RL sensor. To address this issue, we employed the Geant4 simulation tool, allowing for the simultaneous tracking of ionizing radiation and optical photons. In this study, the Geant4-based code, TOPAS, was utilized to conduct Monte Carlo simulations, aiming to gain insights into the radioluminescence signal in an optical fiber RL dosimeter and specifically characterize the stem signal for enhanced measurement accuracy. The simulations encompassed interactions of a medical photon beam from an Elekta linac within a solid water phantom, subsequent energy deposition within the RL sensor, and the generation and transmission of light signals within the optical fiber. Our emphasis was placed on detailed characterization of the light signals originating from both the Ge-doped silica fiber andPMMAtransmission fiber. The primary focus was not only to discern the stem signal from the main signal but also to differentiate between the fluorescence and Cerenkov signals. Importantly, our study showcases how Monte Carlo simulations can be used to spectrally distinguish the stem signal from the scintillation signal of the sensor. This provides valuable information, especially in scenarios where spectrometry is unavailable, contributing to the understanding and refinement of optical fiber RL dosimetry systems....
The dual-fiber optical tweezers have become widespread in trapping, assembling, and sensing due to their simple fabrication process and flexible operation. However, the miniaturization and integration of their displacement measurement optical paths remain challenging. Here, we propose and experimentally demonstrate an integration of structured-light displacement (SLD) measurement method tailored for dual-fiber optical tweezers. A key component split-waveplate is integrated onto the fiber end via coating and etching in the SLD method. The etched fiber and another single mode fiber form optical tweezers, which enables to trap particle and measure its position simultaneously without additional optics. More importantly, it demonstrates a superior signal-to-noise ratio after filtering out the trapping field by the etched fiber. Our results demonstrate a displacement sensitivity reaching the 0.1 pm/Hz1/2 level, which surpasses the performance of most results using the quadrant photodiode method. Ultimately, we discussed the possibilities of using two etched fibers to detect displacements in different directions, or integrating this method into a single optical fiber. This method has significant potential applications in precision sensing, contributes to the integration of optical tweezers and fosters the development of lab-on-fiber applications....
Laser wireless power transfer (LWPT) offers a transformative approach to wireless energy transmission, addressing critical limitations in unmanned aerial vehicles (UAVs) such as battery energy limitation. However, challenges like beam divergence, non-uniform irradiation, and alignment instability limit its practical application. Here, we present a lightweight air-floating metalens platform to overcome these barriers. This innovative lens focuses laser beams near the photovoltaic receiver with an energy distribution uniformity across a single spot at the focal plane that is 50 times greater than that of a conventional Gaussian beam spot, achieving a multi-spot energy distribution uniformity of up to 99% theoretically. Experimentally, we achieved 75% uniformity using a metalens sample. Simultaneously, our system maintains superior beam quality within a dynamic range of 4 m and enhances charging efficiency by 1.5 times. Our research provides a robust technical solution to improve UAV endurance, enabling efficient, long-range wireless power transfer and opening broader technological implications....
Accurately identifying optical fiber vibration signals is crucial for ensuring the proper operation of optical fiber perimeter security warning systems. To enhance the recognition accuracy of intrusion events detected by the distributed acoustic sensing system (DAS) based on phase-sensitive optical time-domain reflectometer (ϕ-OTDR) technology, we propose an identification method that combines empirical mode decomposition (EMD) with convolutional neural networks (CNNs) and long short-term memory (LSTM) networks. First, the EMD algorithm decomposes the collected original optical fiber vibration signal into several intrinsic mode functions (IMFs), and the correlation coefficient between each IMF and the original signal is calculated. The signal is then reconstructed by selecting effective IMF components based on a suitable threshold. This reconstructed signal serves as the input for the network. CNN is used to extract time-series features from the vibration signal and LSTM is employed to classify the reconstructed signal. Experimental results demonstrate that this method effectively identifies three different types of vibration signals collected from a real-world environment, achieving a recognition accuracy of 97.3% for intrusion signals. This method successfully addresses the challenge of ϕ- OTDR pattern recognition and provides valuable insights for the development of practical engineering products....
The three-component accelerometer array has garnered significant attention in seismic wave detection. In this paper, we designed a three-dimensional optical fiber accelerometer based on a circular cross-section cantilever beam and distributed optical fiber strain interrogator. An externally modulated optical frequency domian reflectometry (OFDR) system with centimeter-level spatial resolution is developed to demodulate the dynamic strain on fiber. An algorithm to reconstruct the three-component acceleration from the strain of the optical fiber was derived, and the factors affecting the errors in reconstruction were also investigated. The developed accelerometer exhibits comparable performance to an electrical accelerometer in the experiment. The correlation coefficient between the reconstructed signal waveforms from the two accelerometers exceeded 0.9, and the angular error was less than 8°. The proposed accelerometer is highly compatible with distributed optical fiber sensing technology, presenting significant potential for longdistance array deployment of three-component seismic wave monitoring....
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