Qi Zhang

This article proposes and experimentally demonstrates a corrugated-tube-based fiber-optic sensor capable of measuring pressure, vibration, or both simultaneously. To address the limited sensitivity of conventional diaphragm-based designs, the sensor incorporates an optimized corrugated tube that balances the conflicting stiffness requirements for pressure and vibration measurements. The corrugated tube, acting as a mechanical transducer, is integrated with an extrinsic fiber-optic Fabry–Perot interferometer (EFPI). The EFPI cavity is formed between a reflective surface at the sealed end of the corrugated tube and the cleaved end face of an optical fiber fixed within a mounting assembly. In this configuration, displacement of the corrugated tube induced by pressure and/or vibration directly leads to variations in the EFPI cavity length, which are quantified through interference signal analysis. A series of experiments was conducted using a hydraulic test pump and vibration testing equipment to simulate pressure changes and vibrational disturbances, respectively. The pressure calibration results show a linear relationship between cavity length variation and applied water pressure over a range up to 1 MPa, achieving a sensitivity of −236.75 μm/MPa with a resolution as fine as 10 Pa. Vibration tests demonstrate stable sensor responses over frequencies ranging from 5 to 200 Hz, with an average acceleration sensitivity of approximately 62.49 nm/g. Furthermore, experimental validation confirms the sensor’s capability for simultaneous measurement of pressure and vibration acceleration. With its simple structure, wide measurement range, high sensitivity, excellent mechanical robustness, and minimal temperature sensitivity, the proposed sensor is well suited for practical deployment in demanding industrial environments.

Total Hip Arthroplasty (THA) has been widely adopted as a key orthopedic procedure for restoring hip joint function, where quantitative pressure sensing is critical for optimizing prosthetic alignment and reducing localized stress. However, current clinical practices depend on surgeons' subjective evaluations, lacking objective metrics for biomechanical assessment. Here, a single-fiber embedded acetabular trail is introduced for pressure sensing using multimode fiber (MMF) speckle patterns and CMCNN deep learning network. The MMF-embedded acetabular trail integrates a finite-element-optimized helical fiber path in a 3D-printed acetabular trail, where mechanical deformation under external force induces speckle variations encoding force magnitude and location information. By employing an enhanced convolutional neural network (CMCNN), speckle patterns acquired from discrete pressure applications across 17 spatial regions can be decoded with respect to force loading probe with different configurations and external force locations. Experimental results demonstrate that force between 1–5 N can be accurately quantified, achieving 95.77% recognition accuracy with force and positional variances of 0.235 N and 2.61 mm, respectively. Additionally, new force patterns that are not in the training dataset can be identified with accuracy up to 92.27%, demonstrating CMCNN’s decent generalizability. With compact sensor structure, high sensitivity for force magnitude and position monitoring, the proposed single-MMF embedded acetabular trail not only enables high-fidelity, highly stable pressure sensing for optimizing total hip arthroplasty， but also can be extended to intelligent medical applications.

We demonstrate a double-clad anti-resonant hollow-core fiber (DC-ARF) with an offset inner cladding structure for effective mode tailoring. The DC-ARF consists of six thin-walled, azimuthally offset inner tubes enclosed within a thicker outer cladding tube, which is further connected to silica jacket through a single node. Asymmetric offset arrangement of inner cladding tubes generates two enlarged gaps based on mode field distribution of LP₁₁-like mode, ensuring high-order mode (HOM) suppression. Numerical simulations show that light guidance is achieved through leakage from the larger gaps followed by anti-resonant reflection back into the core. And wavelength disparity between fundamental mode and HOMs provides inherent mechanism for preferential HOM suppression. Through structural optimization, significantly improved mode purity is achieved. The fabricated DC-ARF features two large azimuthal gaps of 70° and operates at a wavelength of 1.06 μm. Experimental results confirm that only the fundamental mode remains when the fiber length exceeds 0.5 m. Furthermore, a 1-m-long DC-ARF improves the input beam quality by approximately 40%, demonstrating its mode tailoring capability. Our work offers valuable guidance for mode tailoring, and the proposed DC-ARF has great potential in single-mode laser transmission, biomedical systems, and optical communications.

We report a compact, single-element long-period fiber grating (LPFG) sensor capable of simultaneously measuring temperature and strain without resorting to cascaded gratings or complex multiplexing schemes. A 4 cm LPFG was fabricated in standard single-mode fiber using CO2-laser exposure and subsequently mounted inside a heat-resistant glass sleeve with a gauge length of 50 mm. Two independent observables-the cladding mode resonance wavelength and the transmission-dip depth-are monitored to decouple the two measurands. Over the temperature range of 22 °C-800 °C, the resonance wavelength exhibits a linear relationship with temperature (sensitivity 0.161 nm/°C, R² > 0.998) with negligible bending crosstalk effects. At a fixed temperature, the transmission-dip depth increases linearly with gauge shortening (-87.7 dB/mm, R² > 0.994) and remains insensitive to thermal loading. By fitting these responses to analytic surfaces and employing a simplified planar model, real-time inversion of temperature and strain is achieved with sub-nanometer and sub-decibel accuracy. Validation experiments conducted on Q235 steel determined its thermal expansion coefficient up to 700 °C, while fire tests on a simply supported steel beam demonstrated reliable curvature sensing capabilities up to 805 °C. This robust, single-element approach offers new avenues for dual-parameter sensing in harsh environments.

In this paper, a novel and cost-effective all-glass microphone with enhanced sensitivity and robustness is introduced, enabled by dual diaphragm structure including pressure amplification diaphragm and acoustic sensing diaphragm. Pressure amplification diaphragm is applied to enhance external acoustic wave, with its focal plane located exactly on the plane of sensing diaphragm, thereby introducing enhanced deflection. Then acoustic introduced deflection is further interrogated interferometrically through the light transmitted by optical fiber. Multi-laser processing method is developed for all-glass microphone fabrication, where picosecond laser is applied for precise diaphragm micromachining and welding, and CO₂ laser is employed for fixing of optical fiber and fiber housing structure. Experimental results demonstrate that the proposed microphone with dual diaphragm achieves a 2.24-fold enhancement in sensitivity at resonant frequency, that is, 206.314 mV/Pa, with signal-to-noise ratio increased from 66.31 dB to 75.68 dB. With advantages of compact size, high sensitivity and enhanced robustness, the proposed all-glass microphone shows strong potential for harsh environment applications.