Yuming Dong

Conventional demodulation methods for fiber-optic Fabry–Pérot (F-P) temperature sensors are limited either by the spectral resolution of wavelength-drift approaches or by spectral leakage in FFT-based phase demodulation. To address these issues, this study proposes a multi-taper FFT full-spectrum phase demodulation method (Multi-Taper FFT-FSPD) for high-precision GaAs F-P temperature sensors. In the proposed dual-band cooperative scheme, the absorption-edge shift of GaAs in the 880 nm band is used for coarse temperature localization and free spectral range (FSR) counting, while high-precision phase demodulation is performed in the 1550 nm band using multi-taper FFT for fine temperature compensation. By combining one Hamming window and two mutually orthogonal DPSS windows through coherent averaging in the complex spectrum domain, the proposed method effectively suppresses spectral leakage and improves dominant-frequency phase extraction. Experimental results show that the proposed sensor achieves a phase sensitivity of 0.235 rad/°C and a demodulation error of ±0.0984 °C. Compared with the traditional wavelength-drift method and the multi-peak average wavelength-drift method, the proposed method improves demodulation accuracy by 63.6% and 38.8%, respectively. These results demonstrate the strong potential of the proposed method for high-precision real-time temperature monitoring.

Accurate measurement of contact forces between medical instrument tips and tissues is a critical challenge in minimally invasive surgery (MIS), where the lack of tactile feedback can compromise surgical precision and safety. To address this, this article presents a novel miniature high-resolution 3-D force sensor based on fiber Bragg grating (FBG) technology. Compared to traditional methods that use multiple optical fibers and complex structures to decouple forces, this sensor employs a cantilever beam structure for biaxial lateral force sensing, while a hollow cylindrical structure is utilized for axial force sensing. This unique combination allows for the independent adjustment of sensitivity in each segment. Finite-element analysis is used to optimize the structure to approximate isotropy. Experiments demonstrate that the sensor achieves an axial force Z resolution of 3.36 mN and a dynamic measurement error of 2.97% within a range of 0–2 N. Meanwhile, lateral force resolutions for X- and Y-directions within a range of −0.5 to 0.5 N are 4.37 and 3.95 mN, respectively, with dynamic measurement errors of 3.79% and 5.12%. Additionally, porcine kidneys are adopted for ex vivo experiments to simulate tumors, validating the feasibility of the designed FBG force sensor in MIS palpation. The simulated vessel identification experiment further validated the ability to detect vessels at different depths within organs, highlighting the potential of the designed sensor for applications in MIS.

This work introduces a novel fiber Bragg grating (FBG)-based tactile sensor specifically developed for real-time force monitoring at the tips of flexible ureteroscopes. With a diameter of only 1.5 mm, the sensor features a dual-FBG configuration that effectively separates temperature effects from force signals, integrated with an innovative elastomer structure based on staggered parallelogram elements. Finite element analyses comparing traditional spiral and parallel groove designs indicate that the new configuration not only enhances axial sensitivity through optimized deformation characteristics but also significantly improves resistance to transverse forces via superior stress distribution and structural stability. In the sensor, a suspended lateral FBG is employed for thermal compensation, while an axially constrained FBG is dedicated to force detection. Calibration using a segmented approach yielded dual-range sensitivities of approximately 283.85 pm/N for the 0–0.5 N range and 258.57 pm/N for the 0.5–1 N range, with a maximum error of 0.07 N. Ex vivo ureteroscopy simulations further demonstrated the sensor’s capability to detect tissue–instrument interactions and to discriminate contact events effectively. This miniaturized solution offers a promising approach to achieving precise force feedback in endoscopic procedures while conforming to the dimensional constraints of standard ureteroscopes.

This paper presents a demodulation method for GaAs fiber optic temperature sensing utilizing reference filters. The method employs a long-pass filter (LPF) waveform as the baseline reference waveform in the wavelength demodulation algorithm, effectively mitigating crosstalk from environmental parameters through the use of passive devices, thereby achieving superior noise resistance in GaAs fiber temperature sensing demodulation. Within the temperature measurement range of -30 to 250 °C, the theoretical wavelength demodulation error of this method can attain the picometer level. The average temperature demodulation error using the cross-correlation algorithm with the LPF waveform as the reference baseline waveform is ±0.388 °C. Compared to existing normalized optical intensity demodulation methods, the refined demodulation algorithm achieves a noise performance enhancement of up to 6.22 times. Moreover, compared to cross-correlation operations without using LPF reference waveform, improvements of up to 2.76 times are achieved.

Magnetic continuum robots offer flexibility and controllability, making them promising for minimally invasive surgery (MIS). However, the clinical application of these robots is relatively limited due to the difficulty of integrating miniaturized triaxial force sensors and their single functionality. This paper proposes a multifunctional magnetic catheter robot with magnetic actuation steering and triaxial force-sensing capabilities. The robot features 3 channels at its tip that integrate multi-segmented magnets, a novel triaxial force sensor, and various functional instruments. The sensor is calibrated, demonstrating high sensitivity and accuracy. The steering characterization of the robot confirms that the catheter tip exhibits effective flexibility and force sensing. Palpation experiments involving various hard lumps are performed on porcine kidney, with results verifying that the robot can reliably detect abnormal hard lumps within tissues. Additionally, palpation experiments in bronchial phantom demonstrate the robot’s imaging and palpation capabilities for lung nodules with an integrated endoscope. Further, the robot, equipped with biopsy forceps, successfully performs palpation and biopsy functions on simulated stomach polyps, demonstrating its capability for effective tissue manipulation. By leveraging force-sensing capabilities and integrating multifunctional instruments, the robot shows potential for expanded applications in MIS, paving the way for important advancements in clinical procedures.

Fiber-based distributed acoustic sensing (DAS) technique has recently captured great attention of academia and industry. The fiber under test (FUT) gains extreme importance for DAS system. However, it is difficult for the commercially available telecom fibers to equip DAS system with long distance, high sensitivity and full distribution. In this work, we have proposed and demonstrated an air-ring microstructure optical fiber (AR-MOF) for fully distributed wideband acoustic sensing with high sensitivity for the first time, to our best knowledge. The cladding of the AR-MOF is constructed by an air-ring for enhancing acousto-optic coupling, and a large mode-area silica core is explored for enlarging the backscattering capture factor. By integrating a 2.2-km AR-MOF into a phase-sensitive optical time-domain reflectometry (Φ-OTDR) system, we have achieved high-sensitivity acoustic detection along the entire FUT within the frequency range from 50 Hz to 5000 Hz. The DAS system shows a maximum acoustic sensitivity of −92.5 dB re rad/μPa at 50 Hz, and an average acoustic sensitivity of −129.4 dB re rad/μPa at the flat area from 500 Hz to 5000 Hz. Compared with previous reports, our AR-MOF based DAS system shows the best sound pressure level sensitivity in such a wide bandwidth. Benefiting from the technical maturity of stack-drawing method and avoidance of nanoparticle doping, the AR-MOF allows for highly sensitive and long-distance DAS system with low attenuation, showing great potential in smart grid, protecting gas pipelines, monitoring of a railway tunnel, illuminating earth phenomenon, real-time intrusion threat detection, marine geophysics, and etc.

A novel fiber extrinsic Fabry-Pérot interferometric ultrasonic sensor for detecting high-frequency ultrasonic signals is proposed and fabricated. The diaphragm structure features an anti-outer-ring clover design. Finite element simulation is employed to determine optimal parameters before directly printing the sensor onto the fiber tip using two-photon 3D printing technique. Experimental results indicate that the sensor achieves a signal-to-noise ratio of 67 dB@300 kHz, a mechanical sensitivity of 1362 nm/kPa, and a noise equivalent acoustic signal level of 3.98 $\mu$Pa/Hz$^{1/2}$ @300 kHz. The proposed fiber sensor offers a new approach for sensing weak ultrasonic signals and is expected to be applied in various ultrasonic detection fields.

To address the optimization problem of expensive multi-modal multi-objective black-box functions, this paper proposes a systematic optimization method based on a back propagation neural network as a proxy model, combined with clustering algorithm to cluster and differentiate multiple modes within the model. The method utilizes normalization and weighted summation of numerical experimental data to optimize the hyperparameters of the optimization algorithm's decision-making process. This approach resolves the multiple constraints of traditional optimization methods. Finally, applied to the hollow-core anti-resonant fiber with gap angle constraints to ensure its topological properties remain unchanged, the model optimizes three categories totaling six modes, optimizing the objectives of birefringence and loss. The top five optimal models achieve a minimum loss of $\text {3.54} \times \text {10}^\text{-3}$ dB/m, maximum birefringence of $\text {1.25} \times \text {10}^\text{-4}$, higher order modulation enhanced receiver of 50, and bandwidth of 1.425 $\mu$m.

This paper develops a high-precision miniature three-dimensional Fiber Bragg Grating (FBG) force sensor designed for detecting and locating hard masses within tissues during Minimally Invasive Surgery (MIS) and robotic-assisted MIS palpation processes. The prototype consists of three FBG-etched optical fibers and an integrated elastomer. The fibers are suspended and parallel to each other within the elastomer, allowing each FBG to be directly compressed or stretched under stress. A novel model, combining segment-by-segment sensitivity and differential decoupling, is adopted for decoupling three-dimensional forces. This approach significantly reduces the crosstalk error caused by spatial forces, avoids the complexity of assembling multiple fibers in previous designs, and reduces the sensor's size, facilitating its integration into MIS procedures. Calibration experiments are conducted to determine the sensor's force sensitivity coefficients, achieving resolutions of 4.35 mN, 3.99 mN, and 3.30 mN in the X, Y, and Z directions, respectively. Through discrete and drag palpation tests on silicone with different types of hard inclusions, the results demonstrate that the proposed prototype has the ability to effectively identify the size, hardness, and depth of hard objects from the contact force information. Additionally, ex vivo porcine kidney palpation experiments are conducted to further verify the feasibility of locating hard masses during MIS palpation.