This study presents a high-sensitivity magnetic field sensing and magnetic particle collective transport strategy based on a microcavity cascade optical tweezer (MCOT) structure. Dual-wavelength laser excitation at 980 nm and 1550 nm enables stable trapping and collective transport of particles (similar to 5 mu m diameter). The captured particle and the fiber tip within the MCOT structure jointly form a Fabry-Perot (F-P) interferometric cavity that responds to external magnetic fields through axial displacement, enabling high-resolution sensing. Under 980 nm laser illumination, capillary microflow force surpasses optical forces, stably guiding particles into the microcavity for trapping. At 1550 nm, thermophoresis induced by strong absorption significantly enhances the propulsion force, successfully transporting particles out of the MCOT structure and enabling efficient collective transport. Combining the reconstruction analysis of axial particle displacement, the system achieves a sensitivity of 2.242 mu m/mT within the 100-280 mT magnetic field range, with a minimum detectable magnetic field strength of 2.16 nT/root Hz. Experimental results closely match simulations. The experimental results align well with numerical simulations, validating the feasibility and reliability of the MCOT structure integrating wavelength-division multiplexing and F-P interference for particle collective transport and magnetic field sensing applications. This approach shows promising potential in biomedical applications, such as studying biological magnetoreception mechanisms or developing magnetically responsive micro actuation systems.

We present a fiber-integrated approach for generating optical-bottle beams based on a microcavity-cascade optical tweezers (MCOT) probe. A 650 nm laser excites the LP21 mode in a single-mode fiber through controlled core offset, and the resulting quadrupolar field undergoes multipath interference inside a thermally tapered microcavity. Internal reflections introduce phase shifts that form closed three-dimensional dark regions surrounded by high-intensity fringes, enabling stable optical-bottle beams. Finite-element simulations and experiments confirm the repeatable trapping and release of low-refractive-index particles in an aqueous environment, demonstrating robust three-dimensional confinement. The fabrication process of the composite fiber probe is straightforward and compatible with fiber-optic integration, providing a compact and tunable platform for particle manipulation. Owing to its simplicity, stability, and scalability, the proposed method offers potential for applications in optical trapping, microfluidics, and bioengineering.

Conventional optical fiber tweezers are constrained by their limited functionality and inability to achieve sequential trapping and cumulative storage of multiple cells. To overcome these limitations, we propose a cascaded microcavity optical tweezer (CMOT) system, which leverages optical-field-dominated multiphysics interactions to enable flexible three-dimensional manipulation of multiple cells within the microcavity and demonstrates three core functionalities with additional extended manipulation capabilities. The CMOT incorporates a tapered microcavity waveguide to establish a stable environment for controlled cell manipulation. It utilizes a continuously focused light field to enable precise orbital guidance of cells. Leveraging the microcavity channel geometry and surface tension, the CMOT induces piconewton-scale capillary forces that autonomously guide cells into the probe, eliminating the need for external equipment for fluid actuation. By harnessing the synergy of tunable optical fields and capillary microfluidic forces, the CMOT enables stable simultaneous trapping of multiple cells at a low power ( P <10 mW ), achieving an order-of-magnitude increase in multi-cell trapping capacity compared to conventional all-fiber optical tweezers. In addition, the CMOT supports selective sorting of cells with different refractive indices and targeted delivery of cells to specific sites. Under additional optical control conditions, the structure also shows preliminary capabilities for array-like reorganization and rotational manipulation. This advancement provides a versatile platform for studying multi-cell heterogeneity, performing quantitative analyses in drug development, and investigating cell dynamics.

Passive mechanoluminescent (ML) fiber pressure sensing enables electrically decoupled pressure measurement, but its performance is limited by the tradeoff between mechanical durability and photon collection efficiency. This work presents a passive ML fiber pressure measurement system (PMPS) by integrating an Archimedean spiral microfiber with a pyramid-structured ZnS:Cu@Al2O3/PDMS ML film. The spiral geometry constructs a two-dimensionally distributed photon collection path within a limited sensing area, improving the spatial matching between localized ML emission and the fiber trajectory, reducing the average emission-to-fiber distance, and mitigating stress localization. Under identical material, excitation, and detection conditions, the spiral configuration achieves a 30.2 % higher photon count than the straight fiber configuration. A length-matched trajectory-driven model predicts a 29.46 % enhancement, indicating that the improvement mainly originates from spatial photon collection path optimization, with curvature-assisted coupling treated as a possible auxiliary contribution. The PMPS exhibits an exponential response over 0-60 N, a linear range of 0-6 N, response/recovery times of 130/90 ms, and stable operation over 10 000 cycles. Handwritten digit recognition demonstrates its capability for trajectory-dependent ML signal encoding.

This paper presents a method for distinguishing particles by converting their refractive-index differences into macroscopic spatial displacements in a cascaded optical tweezers system. Here, the test particle is stably trapped at the fiber tip, acting as an upstream microlens that focuses the incident light and generates a photonic nanojet(PNJ). This jet greatly enhances the axial light-scattering force transferred to the downstream polystyrene microsphere probe, driving its axial displacement. Experiments show that the refractive index of the upstream particle directly determines its effect on the downstream probe: a higher refractive index shifts the probe to a more distant equilibrium position. Using this mechanism, we distinguished yeast cells, silica (SiO₂) microspheres, and polystyrene (PS) microspheres (9–24 μm) by analyzing displacement differences. This method translates microscopic refractive-index differences into intuitive displacements without exogenous labeling or expensive equipment. Its simple design and high visibility present a novel approach to affordable point-of-care testing (POCT) in biomedical and environmental monitoring.

To address the challenge of limited training samples in natural gas pipeline leakage detection, a novel transfer learning framework is proposed, which requires only a small amount of leakage data from a specific leak aperture as the source domain training set. Additionally, a new residual structure, named Dual-Pieces Net, is designed. This structure combines the cross-layer fusion of residual networks with a convolutional fragmenting mechanism. By processing feature maps in various ways through fragmentation, it enhances the model's ability to refine and diversify signal processing. Unlike traditional detection models that rely on large amounts of diverse leakage data, the proposed transfer learning (TL) framework deepens the model's extraction of invariant leakage features from the signal through stacked Dual-Pieces Net modules. This improves the TL performance and provides a solid technical foundation for more diverse TL scenarios. All transfer experiments were conducted on an experimental transport pipeline with a length of 169 m. The experimental results demonstrate that the proposed method offers significant advantages compared to other methods, proving its effectiveness and practical relevance in real-world applications.

We propose a novel single-fiber optical tweezers technology based on mode-division multiplexing (MDM) using LP01, LP11, and LP21 modes. This method enables effective coupling between multimode fibers (MMFs) and single-mode fibers (SMFs) through precise coaxial splicing. By exciting multiple modes in the MMF and employing the SMF for mode filtering, we selectively retain the LP01, LP11, and LP21 modes while effectively suppressing higher order modes. Additionally, we have designed and fabricated an abruptly tapered fiber (ATF) probe to converge the beams of different modes, generating distinct focused light fields at the probe's tip and sides. The simulation and experimental results indicate that this technology can establish multiple stable optical traps, allowing for the effective trapping of several cells. This approach provides precise manipulation tools for studying interactions, such as collective sensing and metabolic cooperation among cells, demonstrating significant application potential, particularly in single-cell analysis, multicellular assembly, and biological micromanipulation.

This study presents an innovative method for the three-dimensional manipulation of cell arrays. The optical tweezers are formed by a combination of nested capillary microcavities and mode-mismatched optical fibers, allowing the LP01, LP11and LP21 mode beams to propagate simultaneously within the microcavity. This configuration enables the formation of two-column and four-column independent cell arrays in both two-dimensional and three-dimensional spaces. Due to variations in their propagation constants, different beam modes generate distinct focal light fields, with higher-order modes creating multiple, well-separated regions. Coupled with the refractive effect of the capillary microcavity on light, this setup generates multiple focal points across several columns within the microcavity. Under the synergistic effect of optical forces and fluid dynamics provided by the microcavity, multiple stable trapping points are generated, allowing cells to achieve stable capture in three-dimensional space. These cascaded optical tweezers with higher-order beams address the miniaturization and three-dimensional manipulation limitations of conventional optical and bottle tweezers, significantly expanding the spatial range for cell capture. It possesses broad application potential, particularly in the medical field for studying collective sensing and metabolic synergistic interactions. Additionally, optical trap arrays hold potential for applications in laser cooling and atomic capture experiments.

This study presents a compact and high-sensitivity sensor based on a reflective optical microfiber coupler (OMC) for temperature and vibration measurements. Embedding the OMC into a polydimethylsiloxane (PDMS) substrate film improves the structural stability of the sensor. The sensor leverages the strong evanescent field characteristics surrounding the OMC, the pronounced reflection effect of the Sagnac loop as the reflector, and the elevated thermo-optical coefficient of PDMS, which collectively improve its sensitivity. We theoretically analyze the optical microfiber coupler Sagnac loop (OMCSL) interference principle and the underlying mechanisms of temperature and vibration sensing. Findings from the experiments indicate that the sensor demonstrates a sensitivity of 2.43 nm/°C within the temperature interval of 35°C-41°C; moreover, it can detect vibration from 30 Hz to 4 kHz. The sensor features compactness, high sensitivity, and low cost.

Conventional electroacoustic sensors face critical limitations in extreme electromagnetic interference (EMI) scenarios such as ultra-high-voltage transmission and particle accelerators, manifesting as sensitivity constraints (SNR < 40 dB for MEMS microphones) and mechanical coupling failures. This study presents a counterpropagating dual-beam fiber-optic acoustic sensing architecture, where two precisely aligned single-mode fiber cores establish an interference field. A nebulizer delivers microparticles to the beam overlap zone, enabling stable optical-axis confinement to form a miniaturized Fabry-Perot resonant cavity. External acoustic perturbations induce particle displacement, which is transduced into optical phase modulation for contactless sensing. Experimental results demonstrate a operational bandwidth spanning 10 Hz-12 kHz with near-unity linearity (R2 = 0.991) and maximum SNR of 57 dB @500 Hz, representing a 17 dB enhancement over conventional piezoelectric counterparts. The system also has high sensitivity, a sensitivity of 334.9 mV/Pa at 500 Hz, and a noise-equivalent pressure of 91.7 mu Pa/root Hz@500 Hz. Rigorous repeatability testing confirms tightly controlled SNR amplitude fluctuations, validating system stability. The compact geometry, inherent EMI immunity, and broadband detection capabilities position this device as a transformative solution for nonlinear single-particle acoustics and industrial monitoring under conditions.

This study presents a microcavity cascade optical tweezer (MCOT) system incorporating wavelength-division multiplexing for collective transport of particles and cells in biomedical applications. The MCOT system traps and transports yeast cells (5 mu m) and silica microspheres using 980 nm and 1550 nm lasers, with a maximum capacity of six particles. Under 980 nm laser illumination, capillary microflow force surpasses optical forces, stably trapping particles and cells in the microcavity. At 1550 nm, significant heat absorption excites thermophoretic forces, which, combined with optical forces, enhance particle transport. Experimental results closely match simulations, confirming the system's potential for efficient particle and cell transport, especially for drug and cell delivery applications. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.

This study proposes an ultra-compact magnetic field sensor based on a single-mode-tapered multimode-singlemode (STMS) structure using a gradient-tapered multimode fiber (TMMF). The sensor employs an axially graded tapering process to finely tune the microstructure of the multimode fiber, which not only enhances modal phase accumulation but also effectively extends the penetration depth of the evanescent field. This leads to a high degree of spatial overlap between the interference phase modulation region and the external magnetic field interaction zone, significantly improving the optical field's sensitivity to magnetic fluid perturbations and its nonlinear response efficiency. Theoretical modeling and simulation analysis further reveal the critical role of the tapered structure in high-order mode excitation, interference phase evolution, and optical field energy distribution. With a compact length of just 2.843 mm, the sensor exhibits a peak sensitivity of 2.16 nm/mT in the 10-16 mT magnetic field range. The repeatability error is as low as +/- 0.0136 %, demonstrating outstanding stability and sensing performance.

This study proposes a self-powered optical sensor based on SrAl2O4: Eu2+, Dy3+ fluorescent particles for simultaneous temperature and pressure detection. The sensor is fabricated by embedding conical optical fibers into a polydimethylsiloxane (PDMS) matrix doped with SrAl2O4: Eu2+, Dy3+ luminescent material. Compared to planar optical fibers, the tapered optical fiber increases the effective area for fluorescence collection, improving light coupling efficiency by 34%. Experimental validation results show an average temperature sensitivity of -0.553 ms degrees C-1 and a pressure sensitivity of 111 pm/Pa. The sensor has a maximum temperature resolution of 0.11 degrees C and a maximum pressure resolution of 11 PA. The sensor demonstrates excellent pressure sensing capability with a loading response time as fast as 137 ms. Additionally, the sensor operates on a cross-sensitivity matrix to simultaneously demodulate temperature and pressure sensing. It addresses the cross-sensitivity challenges in passive multiparameter sensing while eliminating the need for an external power source, offering superior linear response, stability, and repeatability. In the future, this sensor is expected to find widespread application in biochemistry, industrial production, and environmental science and technology.

By tuning cascaded microcavity length and orifice dimensions, this study reveals a light-field modulation mechanism in microcavity optical tweezers, where parameter-optimized configurations (include Field Uniformity and Energy Transfer Efficiency) generate tunable optical gradients at the orifice. Results demonstrate that choosing a microcavity of an appropriate size can enable the light force to dominate at the aperture, supplemented by fluidic force, and generate a more uniform light field. Under these conditions, size-matched particles overcome the optical trapping constraints at the aperture and are captured within the microcavity under the influence of fluidic forces from surrounding weak optical force regions, while other particles are repelled. This achieves particle size sorting. The work clarifies microcavity parameter-dependent optical-hydrodynamic coupling and establishes a synergistic multi-physics manipulation strategy, advancing applications in single-cell sorting and nanodrug screening.

This paper proposes a well-spacing measurement method that integrates magnetic ranging with artificial intelligence, aiming to enhance the detection range and accuracy of magnetic guidance technology for relief wells. Finite element software is used to build models of the active drilling well and the adjacent well. Electrodes and sensors are deployed in the active well during drilling to inject low-frequency alternating current into the formation, magnetizing the casing of the adjacent well. The magnetic field intensity generated by the casing is measured by the sensors, and a novel well-spacing calculation method is developed based on electromagnetic field theory, tailored to the sensor module used in this study. Numerical simulation is carried out using finite element software. The results show that when the well spacing is within 50 m, the calculation error is less than 7%, but the error increases significantly beyond 50 meters. To address this, a multi-layer perceptron (MLP) algorithm is introduced to predict well spacing. The model is trained using data from well H69-3 in Jilin Oilfield to predict spacing in the 50～70 m range, effectively reducing long-distance measurement error. Experimental validation shows that the MLP achieves a root mean square error as low as 0.114～0.161 and a coefficient of determination as high as 0.999 in both randomly partitioned and single-well test scenarios, significantly outperforming traditional methods. The proposed method accurately measures well spacing within 50 m and reduces error in the 50～70 m range using the MLP algorithm, thereby improving measurement precision and expanding the detection range. This presents an innovative solution for magnetic guidance technology with significant engineering application value.

This article presents a control method for radial cell-pair rotations using a single-fiber manipulation technique that combines microcavity cascade optical tweezers with optical fiber mode coupling technology. It explores the mechanisms of cell manipulation under the influence of mode coupling and capillary fluid forces. By controlling the angle of fiber twisting and utilizing the birefringence effect along with the principle of beam mode coupling, it is possible to achieve precise and regular variations in the energy of the LP21 mode beam spot, thereby altering the magnitude and direction of the forces acting on the cell-pair, which induces a tendency for rotational motion. The microcavity cascade optical tweezers provide a small capillary fluid force and serve to isolate the cell-pair from the external environment, allowing it to respond to changes in beam spot energy within a stable microcavity space, thus enabling controllable rotations in both direction and angle. The combination of microcavity cascade optical tweezers with beam mode coupling technology achieves, for the first time, radial cell-pair rotations driven by a single fiber, which holds significant implications for the study of polarized cell migration as well as the investigation of tissue fluidity and connectivity dynamics in cancer prediction.

Low-light image enhancement (LLIE) is mainly used to restore image degradation caused by environmental noise, lighting effects, and other factors. Despite many relevant works combating environmental interference, LLIE currently still faces multiple limitations, such as noise, unnatural color recovery, and severe loss of details, etc. To effectively overcome these limitations, we propose a DICNet based on the Retinex theory. DICNet consists of three components: image decomposition, illumination enhancement, and color restoration. To avoid the influence of noise during the enhancement process, we use feature maps after the image high-frequency component denoising process to guide image decomposition and suppress noise interference. For illumination enhancement, we propose a feature separation method that considering the influence of different lighting intensities and preserves details. In addition, to address the insufficient high-low-level feature fusion of the U-Net used in color restoration, we design a Feature Cross-Fusion Module and propose a feature fusion connection plug-in to ensure natural and realistic color restoration. Based on a large number of experiments on publicly available datasets, our method outperforms existing state-of-the-art methods in both performance and visual quality.

In this study, we propose a novel adjustable rotational half-dome mode conversion for a single-mode fiber (SMF) to generate linearly polarized first-order mode (LP11 mode) and orbital angular momentum (OAM) mode from linearly polarized fundamental mode (LP01 mode). The mode conversion system consists of two modules: the fiber rotation traction (FRT) module, which achieves LP01-LP11 mode conversion by adjusting the rotational angles of theta=45 degrees/135 degrees/225 degrees/270 degrees. Then, elongate it and cut off the optical fiber terminal to form a flat port; and the fiber half-dome lens (FHDL) module, which converts the OAM mode from LP11 mode by fabricating a half-dome lens at the terminal of the FRT module output, introducing two light spots of the LP11 mode with corresponding rotational orthogonal angles. Theoretical and experimental results demonstrate that LP01-LP11 mode conversion can be obtained through our FRT module, and LP11-OAM mode conversion can be generated through our FHDL module. The precise control of the equipment and the model conversion experiment can be made with good robustness and experimental repeatability. Compared with the existing conversion, this mode conversion technique enables the conversion of a single SMF into multiple modes, highlighting its simplicity of operation, which eliminates the necessity for fiber coupling or modulation with optical components. Furthermore, the potential applications of this method extend to optical tweezers particle manipulation experiments. In our future work, we plan to apply this method to enhance the efficiency of particle capture in optical tweezers experiments, leveraging its simplicity and effectiveness.

We propose a new flexible optical fiber magnetic field sensor (FOMS) based on the combination of Michelson interferometer and the PDMS polymer-based optical fiber. The flexible optical fiber magnetic field sensor is made of stretchable elastomer. It uses a stepped refractive index core-cladding structure to achieve effective light confinement, thus enabling stable transmission of light in the waveguide. When the magnitude of the external magnetic field is changed, the micro bending of the sensing region of the optical fiber causes its equivalent refractive index to change, which leads to a drift in the interference spectrum. It is shown that the magnetic field sensitivity of this optical fiber magnetic field sensor reaches -62.8 pm/mT for wavelength detection in the measurement range of 0-200 mT. The FOMS has the characteristics of high sensitivity, good linearity, good temperature response capability, sensitive response, and resistance to electromagnetic interference. In the future, the sensor will have a broad application prospect in medical, geography, aerospace and other fields.

Compound fault signals interfere with one another, resulting in an inconspicuous feature extraction that requires sophisticated signal processing techniques and expert experience. However, good online diagnostic methods are not available to carry out this process. This paper proposes a method based on Residual Connection and Squeeze-and-Excitation Unet (RSEUnet) and one-dimensional convolutional neural network (1DCNN). The process includes fault separation and diagnosis. First, the feature extraction module of the RSEUnet network introduces an attention mechanism and a residual connection that adaptively assigns various weights to different channels. This model is used to train the maps of the fault signal after time-frequency transformation. Ideal binary masks with excellent performance are the training targets to complete the intelligent separation of compound faults. Second, the 1DCNN is used as a feature learning model to efficiently learn the features of single faults from time-domain signals. An embedded system consisting of a Jetson Nano and a signal acquisition circuit is then built to perform online diagnosis. The test is carried out on the fault experimental platform. Results show that the method has an accuracy of 99.71%, making it highly suitable for the diagnosis of bearing compound faults.