Monitoring dam-breaching experiments is challenging because imaging techniques like photogrammetry cannot penetrate turbid, aerated water to track bed elevation changes. This study presents a measurement campaign of small-scale dike breaching experiments using distributed optical fibre sensors (DOFS) to complement photogrammetric measurements. The fibre was placed transversally across the dike below the crest to monitor breach dynamics with minimal flow disturbance. Results show that optical fibre effectively tracks the breach bottom location and deepening process. However, careful post-treatment is necessary since optical fibres are sensitive to temperature gradients from infiltration. Strain and strain rate data distinguish between infiltration effects and mechanical processes such as erosion and block failure. Distributed optical fibre proves to be a promising tool that simultaneously generates valuable data on both infiltration and erosion, offering a powerful complement to traditional non-invasive imaging methods for experimental dam breach monitoring.

Advancement in fast measurement and processing techniques of distributed Brillouin optical time-domain analysis fiber sensors: Methods, challenges, and future directions

MXene-Based Optical Fiber Sensors for Chemical and Biosensing: Review and Perspectives.

Traditional firefighting clothing plays a crucial role in protecting firefighters from burn injuries through its passive heat insulation performance. However, current firefighting garments still face a challenge in dealing with complex and changeable rescue scenarios due to their insufficient risk warning capability for firefighter safety. Herein, we propose a wearable bimodal fiber sensor with a core-sheath structure, which incorporates an engineered mesoporous Ti3C2Tx and a Ti3C2Tx/SnSe heterojunction integrated into an aramid nanofiber substrate for monitoring exposed ammonia gas and temperature in firefighting clothing. The outer shell of sensing fiber is composed of mesoporous Ti3C2Tx, featuring active edge-Ti-O sites, while the MXene and SnSe in the core layer of the sensing fiber create nanoscale Schottky junctions that facilitate an energy filtering effect. The resulting chemical resistance-type gas sensing fiber sheath provides an ultrafast response time (9 s) and high sensitivity (41.76% @ 8 ppm) in detecting NH3. Additionally, due to the energy filtering effect of the nanoscale Schottky junction between Ti3C2Tx and SnSe, the sensing fiber core exhibits high thermoelectric sensitivity (S = 560 μV K-1 from 130 to 320 °C), super-resolution (1 °C), and a wide temperature monitoring range (-20 to 320 °C). To facilitate wearable applications, the sensing signals from the monitoring system are transmitted wirelessly via Bluetooth and displayed on a smartphone, enabling multidirectional dynamic warnings for NH3 and overheating alerts in firefighting clothing. This work significantly advances the implementation of wearable gas and temperature warning sensors in firefighting clothing for enhancing firefighter safety.

State-aware deformation sensing of compliant medical balloons is desirable for understanding their boundary-dependent working states, but remains challenging because large deformation, low stiffness, and local contact can produce mechanically coupled responses. Although stretchable fiber sensors are attractive because of their miniature size and mechanical compliance, conventional single-channel designs often merge axial strain, radial compression, and local contact into one electrical output, making deformation-mode discrimination difficult. Here, we report a highly stretchable liquid-metal coaxial fiber sensor (LM-CFS) for complex deformation-mode discrimination in balloon-like soft systems. The LM-CFS consists of a liquid-metal core, a thin silicone dielectric layer, and a carbon-nanotube/silicone composite shell. This coaxial structure provides two complementary electromechanical pathways: the core resistance Rcore is highly sensitive to localized constriction of the liquid-metal pathway, whereas the coaxial capacitance Ccoax primarily tracks distributed geometric reorganization and axial strain. By mapping the signal changes into a ΔRcore-ΔC phase space, uniaxial stretching, full-length radial compression, and local compression can be distinctly resolved. The internally confined coaxial capacitive geometry also reduces proximity-induced capacitance disturbance from nearby conductive or high-permittivity surroundings. When integrated onto a balloon model, a single fiber decodes free expansion, wrinkle formation, distributed confinement, and localized contact into interpretable phase-space branches. This work provides a compact and mechanism-interpretable sensing strategy for monitoring complex deformation states in balloon-like compliant biomedical interfaces.

Basalt fibers (BFs) are promising substrates for the fabrication of physical sensors owing to their excellent mechanical strength, thermal stability, and corrosion resistance. However, their inherent electrical insulation and inert surface chemistry severely hinder the development of high-performance fiber-based sensing devices. To address these limitations, we propose a synergistic surface modification strategy involving sequential KOH activation, fluorinated silane coupling agent (FAS-13) functionalization, and surface coating of a hybrid conductive layer of graphene oxide (GO) and carbon nanostructures (CNS). KOH etching increases basalt fiber surface roughness and exposes silanol (-Si-OH) groups to provide active sites for subsequent covalent grafting of FAS-13 to enhance interfacial adhesion. The GO/CNS hybrid leverages the functional groups of GO for improved dispersion of CNS and electrical conductivity to establish a robust three-dimensional conductive network. The resulting composite fiber (MFBFCG) exhibits outstanding electrical conductivity (∼230 S m-1), a high temperature coefficient of resistance (TCR) of 0.18% per °C and excellent signal linearity (R2 > 0.999) within 30-150 °C, as well as a rapid pressure response (response/recovery times of 78.0 ms and 62.8 ms). This work provides a novel and effective strategy to engineer multifunctional fiber sensors, showcasing their potential applications in smart textiles, aerospace thermal management, and industrial pressure monitoring systems.

ABSTRACT This study presents the development and optimization of a multi-D-shaped optical fiber sensor designed for enhanced refractive index (RI) and ethanol detection. The sensor probes were fabricated using a precise side-polishing technique on standard single-mode fiber (SMF-28) to maximize the evanescent field interaction with the surrounding medium. We systematically investigated the influence of the number of D-shaped sensing zones ( N = 1 to 5) on sensor performance using glycerin-water solutions (RI 1.357–1.428). The experimental results demonstrate a significant sensitivity enhancement as the number of sensing zones increases, achieving a peak sensitivity of 12.12 dB/RIU with a 4-point ( N = 4) configuration. A subsequent performance decline at N = 5 indicated a saturation limit dominated by fundamental mode field distortion and cumulative insertion loss. When applied to ethanol detection (RI 1.333–1.365), the optimized 4-point sensor exhibited a highly linear response (R2 = 0.9828) with a sensitivity of 3.866 dB/RIU. Notably, the sensor demonstrated high wavelength stability with negligible spectral shift across the tested range, confirming its operation as a robust, intensity-modulated device suitable for cost-effective biochemical sensing applications.

Fiber electronics have shown considerable potential in various applications, including electronic skin, human-machine interfaces, and intelligent sensing systems. However, stretchable fiber-based strain sensors confront fundamental challenges in concurrently achieving robust mechanical endurance, wide linear response range, and effective composite motions decoupling under complex deformation conditions. Here we present a highly stretchable tri-channel fiber featuring concentric and double-helical microchannels integrated with gallium-based liquid metal, constructing a dual-strain fiber sensor capable of decoupling composite motions involving both elongation and torsional deformations. The helical architecture promotes a three-dimensional orientation of polymer chains, thereby effectively enhancing both the stretchability and cyclic durability of the sensor. Owing to the specific configuration within the fiber, the sensor exhibits a highly linear response to tensile strain, along with bidirectional torsional strain sensing across a wide operational range. Furthermore, by synergistically integrating geometric deformation with hybrid resistive-capacitive sensing mechanisms, the sensor demonstrates the ability to simultaneously monitor and decouple stretching and twisting composite motion behaviors. This strategy enables the precise characterization of object motion and deformation states, offering valuable prospects for real-time health monitoring and motion tracking applications.

This work presents an intrinsic optical fiber sensor based on plasmonic phenomena in modified plastic optical fibers (POFs). The sensing area is achieved by replacing the polymethyl methacrylate (PMMA) core with a molecularly imprinted polymer (MIP) containing gold nanorods (GNRs). Thus, in the sensing area, the MIP acts as both a selective recognition element and an optically sensitive guiding medium where plasmonic phenomena occur. This optical–chemical configuration has been developed as a proof-of-concept for the detection of furfural in aqueous solution. The proposed sensor achieves a limit of detection (LOD) of 27 pM, demonstrates high selectivity for the analyte of interest, and is applicable even in real-world scenarios, as demonstrated by experimental results (a commercially available infant milk). The proposed sensor presents a significant enhancement of the sensor response, of about six orders of magnitude, compared to a conventional configuration where the same (or a similar) mixture of MIP/GNRs is spun over the exposed PMMA of a D-shaped POF area for comparison. Notably, even if this study has been carried out via a proof-of-concept in furfural detection, this substantial improvement is achieved while preserving a simple, portable, and cost-effective optical setup, highlighting the potential of this sensing strategy for the development of highly selective sensors by changing the MIP template.

β-Galactosidase (β-Gal), a key senescence biomarker, is crucial for early diagnosis and treatment. In this work, a portable fluorescent fiber optic sensor, based on hydrogel technology, has been designed to monitor β-Gal activity. A tapered optical fiber probe was functionalized with green-emitting silicon quantum dots (SiQDs) via in situ hydrogel polymerization. The sensor ingeniously exploits a β-Gal-initiated cascade reaction: the hydrolysis of the substrate by β-Gal releases a reductant, which promotes the conversion of the Cu(II) chelate into its chromogenic Cu(I) counterpart; the resultant Cu(I) species, in turn, quench the fluorescence of SiQDs via an inner-filter effect. This sensor showed a linear response for β-Gal between 2.0 and 15.0 U L-1, achieving an analytical sensitivity threshold of 1.60 U L-1. It exhibited a combination of high sensitivity, excellent selectivity, strong anti-interference capability, facile fabrication and portability. The sensor accurately quantified β-Gal in real serum and urine samples, with reliability confirmed through standard-addition recovery tests. This represents a mobile, highly effective approach for online, ultratrace β-Gal activity detection in biological specimens and opens new avenues for portable biosensor development.

Balloon-Shaped Mach-Zehnder fiber sensor functionalized with CS-PMAA for trace Cr(VI) detection in water

Optical fiber sensing offers inherent advantages in long-distance and interference-free transmission. However, it faces a major challenge in achieving self-decoupling and multimodal detection. Here, inspired by the firefly's bioluminescent mechanism, we propose a flexible, distributed, multimodal electrical-sensing-optical-transmission fiber sensor (ESOT FiSensor) that can convert diverse electrical sensing signals into optical signals through on-fiber hybrid circuits. The ESOT FiSensor realizes distributed and simultaneous monitoring of four physical parameters, including vibration, pressure, temperature, and strain, through only a single optical fiber, and it can maintain long-distance transmission and strong electromagnetic interference immunity within 0-1000Hz, far superior to purely electrical sensors. The on-fiber electro-optical circuits were fabricated by combining conformal additive printing and flexible hybrid electronics integration, and the printing technique achieves a resolution of 260nm directly on submillimeter fibers as fine as human hair (∼60μm). The performance of the ESOT FiSensor has been validated in three representative scenarios: multimodal sensing under complex environmental conditions, distributed sensing on aircraft skins, and wearable sensing for human-machine interaction. The ESOT FiSensor establishes a powerful and scalable platform for long-distance, multimodal signal perception in complex and dynamic environments. It provides a pathway toward transforming optical fibers from passive communication media into active multimodal distributed sensing networks in the near future.

Testing and evaluating long-term prestress loss of steel strand in LNG storage tank using optical fiber sensor and explainable machine learning

A lab-in-a-fiber sensor platform is demonstrated, enabling simultaneous optical analysis and controlled microfluidic transport in a single monolithic device. It consists of a high-aspect-ratio flat fiber (HARFF) that integrates a mechanically compliant elliptical fused silica capillary and a Ge-doped single-mode waveguide. The waveguide, partially exposed to the capillary, provides evanescent field interaction with analytes introduced into the central microfluidic channel. The high-aspect-ratio microfluidic channel confines side wall effects, producing a flattened laminar flow that supports stable real-time imaging. Alongside particle-flow monitoring, the device exhibits a tunable refractive-index sensitivity. Through in-plane flexure, a more than three-fold sensitivity enhancement was demonstrated at a 50 mm bending radius over a straight fiber. This hybrid fiber sensor design represents cost-effective production of a compact and versatile platform for lab-in-fiber applications, combining optical interrogation and microfluidic functionality.

Optical fiber sensors reveal in-situ thermo-mechanical behaviors inside silicon-based lithium-ion batteries

All-inorganic perovskite CsPbBr₃-assisted Mach-Zehnder Interferometer (MZI) optical fiber sensor for highly sensitive ultraviolet and blue light detection

In situ plasmonic optical fiber sensor for dynamic reaction process and intermediate behavior analysis

Phase-specific detection of CO2 at sequestration pressure using mid-infrared fluoride fiber sensors

Operando monitoring of health and overcharge warning in lithium-ion battery with high-sensitivity, small-diameter optical fiber sensor

Fibre optic sensors are widely used to monitor structural deformation. In conventional systems, the optical sensing signals are first converted into electrical signals for subsequent processing by integrated circuits, and the results are then displayed on external devices. As a result, traditional fibre optic sensors generally only have sensing capabilities and lack the ability to directly convey information about the detected deformation. This paper presents a fibre optic sensing strategy that integrates both sensing and expression, using a pair of dissipative optical fibre sensors embedded in a deformable, translucent soft material. Through the structural design of optical fibres, the optical fibres generate directionally related light leakage when bending the fibres. The spatial information associated with the bending is encoded in colour by the sensor pair and shown on the soft material, thereby expressing its spatial information to the outside world. This allows real-time, visual expression of spatial status-related information. This strategy extends the functional boundaries of fibre optic sensors, from passive sensing to sensing and colour expression. This integrated sensing-expression approach could offer rapid-response interaction for some applications in systems such as soft robots and wearable devices. • A fibre optic sensor pair embedded in soft material enables simultaneous deformation sensing and direct colour expression. • Directionally controllable light leakage encodes bending-related spatial information into visible colours without electronic processing. • The integrated sensing–expression strategy provides real-time visualisation for soft robots, wearable devices, and other interactive systems.