Fiber Axis Research Articles

Absorption of hybrid fibre modes by Cs atoms in quadrupole transitions

We evaluate the rate of the absorption of an optical nanofibre mode by a Cs atom in an electric quadrupole transition. With the Cs atom localised near the outer surface of the optical nano-fibre, an interaction occurs between the atomic quadrupole tensor components and the gradients of the vector components of the electric field of a hybrid fibre mode. The absorption rate is evaluated as a function of the radial position of the atom from the fibre axis, assuming a specific value of the laser power and we use experimentally accessible parameters. We find that the absorption of the hybrid modes by the Cs atom decreases as the atom recedes away from the fibre axis and it formally vanishes at sufficiently large radial distances. Close to the fibre, however, the absorption rate for the input power chosen can be two orders of magnitude larger than the quadrupole de-excitation rate despite the moderate power used.

X-ray study on crystalline morphology in iPP/MMT nanocomposite fibers

Nanocomposite fibers based on isotactic polypropylene (iPP) and an organically modified montmorillonite (MMT), Cloisite 15A, were formed from the melt at different take-up velocity. The studies were performed for pure iPP fibers and fibers containing three different concentrations of MMT. The supermolecular structures of the fibers at the crystallographic and lamellar levels were examined by means of X-ray scattering methods (WAXS and SAXS). It was found that the dominant crystal form of iPP is α modification. The increase of take-up velocity induces the orientation of iPP crystals parallel to the fiber axis. The cross-hatching crystallization of iPP was also observed in the tested fibers. Only for the gravity spun fibers containing MMT, the β modification of iPP was observed. Assuming that nucleation does not occur on the surfaces of clay platelets but rather in the interlayers of MMT particles, a probable β-phase nucleation mechanism has been suggested. This mechanism was confirmed by the isothermal crystallization experiment. During heating, the β crystalline form transformed into α-form. The degree of transformation depended on the annealing temperature. The studies also revealed that lamellar stacks of iPP are perpendicular to the MMT layers surfaces.

Effect of Forearm Postures and Elbow Joint Angles on Elbow Flexion Torque and Mechanomyography in Neuromuscular Electrical Stimulation of the Biceps Brachii.

Neuromuscular electrical stimulation plays a pivotal role in rehabilitating muscle function among individuals with neurological impairment. However, there remains uncertainty regarding whether the muscle's response to electrical excitation is affected by forearm posture, joint angle, or a combination of both factors. This study aimed to investigate the effects of forearm postures and elbow joint angles on the muscle torque and MMG signals. Measurements of the torque around the elbow and MMG of the biceps brachii (BB) muscle were conducted in 36 healthy subjects (age, 22.24 ± 2.94 years; height, 172 ± 0.5 cm; and weight, 67.01 ± 7.22 kg) using an in-house elbow flexion testbed and neuromuscular electrical stimulation (NMES) of the BB muscle. The BB muscle was stimulated while the forearm was positioned in the neutral, pronation, or supination positions. The elbow was flexed at angles of 10°, 30°, 60°, and 90°. The study analyzed the impact of the forearm posture(s) and elbow joint angle(s) on the root-mean-square value of the torque (TQRMS). Subsequently, various MMG parameters, such as the root-mean-square value (MMGRMS), the mean power frequency (MMGMPF), and the median frequency (MMGMDF), were analyzed along the longitudinal, lateral, and transverse axes of the BB muscle fibers. The test-retest interclass correlation coefficient (ICC21) for the torque and MMG ranged from 0.522 to 0.828. Repeated-measure ANOVAs showed that the forearm posture and elbow flexion angle significantly influenced the TQRMS (p < 0.05). Similarly, the MMGRMS, MMGMPF, and MMGMDF showed significant differences among all the postures and angles (p < 0.05). However, the combined main effect of the forearm posture and elbow joint angle was insignificant along the longitudinal axis (p > 0.05). The study also found that the MMGRMS and TQRMS increased with increases in the joint angle from 10° to 60° and decreased at greater angles. However, during this investigation, the MMGMPF and MMGMDF exhibited a consistent decrease in response to increases in the joint angle for the lateral and transverse axes of the BB muscle. These findings suggest that the muscle contraction evoked by NMES may be influenced by the interplay between actin and myosin filaments, which are responsible for muscle contraction and are, in turn, influenced by the muscle length. Because restoring the function of limbs is a common goal in rehabilitation services, the use of MMG in the development of methods that may enable the real-time tracking of exact muscle dimensional changes and activation levels is imperative.

Vector pure-quartic soliton molecule fiber laser

Pure-quartic solitons (PQSs) balanced by the fourth-order dispersion (FOD) and nonlinearity in weakly birefringent optical fibers exhibit unique characteristics that differ from those of traditional solitons. Owing to the long oscillating tail of the PQS, soliton trapping can be easily promoted either between the sub pulses inside the molecule or along the two polarization axes of the birefringent fiber. Thus, observing the interaction and motion dynamics of vector PQS molecules promotes great opportunities for unveiling new mechanisms of soliton molecular complexity. In this work, we numerically explore the transient dynamics of vector PQS molecules by solving the coupled Ginzburg-Landau equations which are contributed by the FOD. Diverse real-time dynamics of vector PQS molecules are demonstrated for the first time, including stationary and pulsating, which originate from the multi-scale energy exchange inside the molecule and between the orthogonal axes depending on the nonlinear effect. In addition, we reveal that the buildup process of vector PQS molecules includes splitting, pulsating, and synchronization. The related dynamics of the pulse separation and phase difference that constitute the relevant internal degrees of freedom of the molecule are also mapped. These efforts may shed new insights into understanding the internal dynamics of soliton molecular complexes and decomposing the dynamics of complex nonlinear systems.

Reconstructed Hierarchically-Structured Keratin Fibers with Shape-Memory Features Based on Reversible Secondary Structure Transformation.

Biocompatible and biodegradable shape-memory polymers have gained popularity as smart materials, offering a wide range of applications and environmental benefits. Herein, we investigate the possibility of fabricating regenerated water-triggered shape-memory keratin fibers from wool and cellulose in a more effective and environmentally friendly manner. The regenerated keratin fibers exhibit comparable shape-memory performance to other hydration-responsive materials, with a shape fixity ratio of 94.8 ± 2.15% and a shape recovery rate of 81.4 ± 3.84%. Owing to their well-preserved secondary structure and crosslinking network, keratin fibers exhibit outstanding water-stability and wet stretchability, with a maximum tensile strain of 362 ± 15.9%. In this system, we investigate the reconfiguration of the protein secondary structure between α-helix and β-sheet as the fundamental actuation mechanism in response to hydration. This responsiveness is studied under force loading and unloading along the fiber axis. Hydrogen bonds act as the "switches" clicked by water molecules to trigger the shape-memory effect, while disulfide bonds and cellulose nanocrystals play the role of "net-points" to maintain the permanent shape of the material. Water-triggered shape-memory keratin fibers are manipulable and exhibit potential in the fabrication of textile actuators, which may be applied in smart apparel and programmable biomedical devices. This article is protected by copyright. All rights reserved.

In-line temperature-compensated vector magnetic field sensor with side-polished fiber.

A novel, to the best of our knowledge, vector magnetic field sensor with temperature compensation is proposed and investigated. The proposed sensor is realized by side polishing a multi-mode optical fiber and adopting the surface plasmon resonance (SPR) effect. The side-polished surface is coated with a magnetic fluid (MF) and polydimethylsiloxane (PDMS) successively along the fiber axis. The as-fabricated sensor can be used not only for magnetic field strength and direction sensing, but also for temperature detection. The achieved magnetic field intensity sensitivities are 1720 pm/mT (90° direction) and -710 pm/mT (0° direction), and the temperature sensitivity is -2070 pm/°C. On top of its temperature compensation ability, the easy fabrication and very high sensitivity of the proposed sensor are attractive features for vector magnetic field sensing applications.

Spider dragline silk fibres maintain rectangular columnar liquid crystalline phase

ABSTRACT The liquid crystalline phase of spider silk is thought to enable for the silk protein to be stored at high concentration in the gland without gelation, facilitating the instant fibre formation at the spinning duct. Nevertheless, it has never been revealed whether the liquid crystalline state of the silk protein maintains after the fibre formation. In this study, we conducted the X-ray liquid crystal structure analysis to reveal the details of molecular assemblies of the native spider silk proteins. Based on the wide- and small angle X-ray scattering data using the uniaxial bundle of spider draglines, the spider dragline silk fibres maintain a rectangular columnar liquid crystalline phase with a P21/a (p2gg) symmetry. The liquid crystalline state of the spider silk fibre is not nematic, cholesteric, nor hexagonal columnar, as previously proposed, but rectangularly packed columnar liquid crystal. The movable silk molecular chains along the long fibre axis in the rectangular columnar liquid crystalline structure help to explain the mechanical strength of the native spider dragline silk fibres. The results obtained in this study will contribute to understanding the biological basis underlying the silk fibre formation and will be useful to the biomimicry of spider silk fibres.

Comparison study on bending properties and failure of 3D5d and 3D6d carbon/phenolic braided composites at room and elevated temperatures

Three-dimensional five-directional and six-directional braided composites (3D5dBCs and 3D6dBCs) are widely used in aerospace industry for their excellent axial and transverse properties. This work successfully fabricated 3D5dBCs and 3D6dBCs with carbon/phenolic, and compared their bending properties and failure mechanisms at room and high temperatures (RT and HT). The influences of braiding structure and temperature on bending properties and failure mechanisms of 3D5dBCs and 3D6dBCs were analyzed. The load/deflection curves are linear elastic at RT, showing prominent plastic characteristics at HT. From RT to HT, the bending properties decrease, but 3D5dBCs always have higher bending properties than 3D6dBCs. The 3D5dBCs and 3D6dBCs are primarily damaged near the surface at RT; fiber shearing fracture feature becomes apparent and the interior damage worsens at HT. 3D5dBCs exhibit obvious shear failure mode, where the fracture is bent and rough, and the damage patterns are braiding and axial fibers shearing fracture, matrix softening, and interface debonding. 3D6dBCs show transverse sawtooth fracture cracks, and the damage mechanisms are braiding fiber shearing fracture, fifth fiber tearing, sixth fiber shedding and pulling-off, matrix plasticization, and interface debonding.

Spider Silk Protein Forms Amyloid-Like Nanofibrils through a Non-Nucleation-Dependent Polymerization Mechanism.

Amyloid fibrils-nanoscale fibrillar aggregates with high levels of order-are pathogenic in some today incurable human diseases; however, there are also many physiologically functioning amyloids in nature. The process of amyloid formation is typically nucleation-elongation-dependent, as exemplified by the pathogenic amyloid-β peptide (Aβ) that is associated with Alzheimer's disease. Spider silk, one of the toughest biomaterials, shares characteristics with amyloid. In this study, it is shown that forming amyloid-like nanofibrils is an inherent property preserved by various spider silk proteins (spidroins). Both spidroins and Aβ capped by spidroin N- and C-terminal domains, can assemble into macroscopic spider silk-like fibers that consist of straight nanofibrils parallel to the fiber axis as observed in native spider silk. While Aβ forms amyloid nanofibrils through a nucleation-dependent pathway and exhibits strong cytotoxicity and seeding effects, spidroins spontaneously and rapidly form amyloid-like nanofibrils via a non-nucleation-dependent polymerization pathway that involves lateral packing of fibrils. Spidroin nanofibrils share amyloid-like properties but lack strong cytotoxicity and the ability to self-seed or cross-seed human amyloidogenic peptides. These results suggest that spidroins´ unique primary structures have evolved to allow functional properties of amyloid, and at the same time direct their fibrillization pathways to avoid formation of cytotoxic intermediates.

A time-based double-sided readout concept of 100 mm LYSO:Ce,Ca fibres for future axial TOF-PET

BackgroundPositron emission tomography (PET) requires a high signal-to-noise ratio (SNR) to improve image quality, with time-of-flight (TOF) being an effective way to boost the SNR. However, the scanner sensitivity and resolution must be maintained. The use of axially aligned 100-mm LYSO:Ce,Ca scintillation crystals with double-sided readout has the potential of ground-breaking TOF and sensitivity, while reducing parallax errors through depth-of-interaction (DOI) estimation, and also allowing a reduction in the number of readout channels required, resulting in cost benefits. Due to orientation, these fibres may also facilitate the integration of TOF-PET with magnetic resonance imaging (MRI) in hybrid imaging systems. The challenge of achieving a good spatial resolution with such long axial fibres is directly related to the achievable TOF resolution. In this study, the timing performance and DOI resolution of emerging high-performance materials were investigated to assess the merits of this approach in organ-dedicated or total-body/large-scale PET imaging systems.MethodsLYSO:Ce,Ca scintillation fibres of 20 mm and 100 mm length were tested in various operating and readout configurations to determine the best achievable coincidence time resolution (CTR) and DOI resolution. The tests were performed using state-of-the-art high-frequency (HF) readout and commercially available silicon photomultipliers (SiPMs) from Broadcom Inc.ResultsFor the 100-mm fibre, an average CTR performance of 137 pm 1 ps FWHM and an average depth-of-interaction resolution within the fibre of 12.3 pm 0.5 mm FWHM could be obtained. The 20-mm fibre showed a sub-100 ps CTR of 98 pm 1 ps FWHM and a fibre resolution of 8.5 pm 0.2 mm FWHM in the double-sided readout configuration.ConclusionWith modern SiPMs and crystals, a double-sided readout of long fibres can achieve excellent timing resolution and field-advancing TOF resolution, outperforming commercial PET systems. With 100-mm fibres, an electronic channel reduction of about a factor 2.5 is inherent, with larger reduction factors conceivable, which can lead to lower production costs. The spatial resolution was shown to be limited in the axial direction with 12 mm, but is defined to 3 mm in all other directions. Recent SiPM and scintillator developments are expected to improve on the time and spatial resolution to be investigated in future prototypes.

Fast transport diffusion of bound water in cellulose fiber network

AbstractA remarkable property of cellulose-based materials is that they can absorb huge amounts of water (25% of the dry mass) from ambient vapor, in the form of bound water confined at a nanoscale in the amorphous regions of the cellulose structure. The control of the dynamics of sorption and desorption of bound water is a major stake for the reduction of energy consumption and material or structure damages, but in the absence of direct observations this process is still poorly known. Here we present measurements of bound water transport thanks to Nuclear Magnetic Resonance relaxometry and Magnetic Resonance Imaging measurements. We show that the bound water is transported along the fibers and throughout the network of fibers in contact. For each material a single transport diffusion coefficient value allows to represent the processes over the whole range of saturation. The dependence of the transport diffusion coefficient on the fiber density and orientation is then analyzed to deduce the (elementary) transport diffusion coefficient of bound water along a cellulose fiber axis. This constitutes fundamental physical data which may be compared with molecular simulations, and opens the way to the prediction and control of sorption dynamics of all cellulosic materials or other hygroscopic materials.

Novel continuous fiber bending experiment to determine size- and spatial-distribution of surface defects in glass fibers

Tensile strength models for unidirectional composites require scaling of fiber strength distributions to small length scales in the range of the fiber radius to the ineffective length (5–200 μm). No test methods currently exist to measure and validate fiber strength at these length scales. In this paper, a novel continuous fiber bending test method is developed to measure the size and spatial distribution of defects in S-glass fibers. For this test method, a single glass fiber was placed between Kapton film and tape, and the sample is subjected to a sequence of controlled radii of curvatures ranging from 350 μm to 25 μm in a confocal microscope. From the bending tests, the number of defects and spacings between the defects over 780 mm length of fiber are obtained for each level of flexural stress. The Kapton film confines the fiber fragments and maintains fiber alignment allowing the same sample to be tested at lower radius of curvature (higher flexural strain/stress). The associated defect size is calculated using fracture mechanics. These results are used to map the size- and spatial-distribution of critical defects on the tension surface of a glass fiber. A methodology is presented to map additional defects around the circumference of the fiber, while maintaining the size and spatial distribution obtained from the bending tests. The results show that the lognormal distribution best fits the spatial distribution of defects along the fiber axis. The results also indicate that extrapolating the Weibull strength distribution (be it bimodal or unimodal) to gage lengths less than 200 μm leads to serious errors in fiber strength prediction.

Study on anisotropic heat transfer and thermal damage in nanosecond pulsed laser processing of CFRP

AbstractNanosecond pulsed laser processing is an efficient method of processing carbon fiber reinforced plastic(CFRP), which is widely used in the manufacturing field of aviation, medical, and auto industries. The anisotropic heat transfer of carbon fiber is a key factor degrading the surface integrity of laser processing CFRP. So it is urgent to explore the significant mechanism of anisotropic heat transfer of laser interacting with CFRP. A novel numerical model considering anisotropic heat transfer was established to analyze heat transfer and thermal damage of CFRP laser machining. By comparison of simulation and experiments, the average error of ablation depth and width ranges from 4.71% to 15.09%, so the model could precisely simulate the CFRP laser machining. It demonstrates that the heat conductivity along the axial carbon fiber is higher than that along the radial, resulting in an elliptical ablation morphology. And when the laser scanning direction is parallel to the direction of the carbon fiber, deeper and narrower microgrooves can be obtained. In addition, laser processing at the edge of the CFRP plate causes serious heat accumulation, leading to severe thermal damage. The simulation and experiments were conducted to explore the effect of parameters including laser energy, scanning speed, and scanning space on the depth and width of laser ablation. A deeper micro‐channel with a smooth machined surface and small thermal damage was obtained when laser energy E = 0.275 mJ, scanning speed v = 630 mm/s, and scanning space h = 21 μm.

Factors affecting axial and lateral load transfer of hollow fibre-reinforced polymer piles in soft clay

ABSTRACT The growing interest in the long-term performance of pile foundations and their ability to resist the negative effects of water exposure and aggressive environmental conditions has led to considering non-corrosive materials such as fibre-reinforced polymer (FRP). The most common applications are light-bearing structures in waterfront environments, while applications for larger structures have not been widely accepted in industry due to the lack of long-term records and design guidelines available. In this study, a numerical model using the finite element method was developed to simulate small-scale load tests of hollow carbon-fibre reinforced polymer (CFRP) and glass-fibre reinforced polymer (GFRP) piles in soft clay. The findings of this research indicate that the number of FRP layers impacts loading behaviour significantly, while inner tube soil height has a reasonable influence on axial load response and fibre orientation has a minor effect under lateral load conditions.

Nanomaterial-Functionalized Tilted Fiber Gratings for Optical Modulation and Sensing

The tilted fiber grating (TFG) is a special grating whose grating planes are slanted or blazed relative to the fiber axis. These tilts in the planes break the cylindrical symmetry of the fiber, strongly enhance the light coupling from the fiber core to cladding, and resonantly excite a large number of cladding modes. Then, the TFGs with rich spectral information and strong evanescent field leaking out open up a multitude of opportunities for the enabled light-matter interaction by functionalizing their surface with nanomaterials. In this review, we briefly analyze the architectures, coupling mechanisms, spectral properties, and implementations of different TFGs, including weakly tilted Bragg grating with small tilt angle, radiated TFG with 45° tilt angle, excessively TFG with large tilt angle, etc. Further, the sensing enhancement and spectral modulation by integrating layered nanomaterials on TFGs are discussed, which could be considered as a promising strategy to break the limitation of fiber's one-dimensional structure and promote the light-matter interaction for enhanced and extended applications in optical parameter modulation and sensing.

Grism fabricated on the end-face of an optical fiber.

We designed and fabricated grism structures on the end-face of an optical fiber and experimentally characterized them. A UV-curable ionic-liquid polymer resin, well-suited for nanoimprinting, was used to fabricate the grism structures with grating pitches of 1.8-3 µm and prism apex angle reaching 30-40°. The structures can propagate 1st order of diffraction peaks along the fiber axis at 520, 660, and 830 nm wavelengths. The experimental and numerically simulated results of far-field intensity distribution revealed high agreement. Hence, based on the numerical simulation, we proposed grism structure designs for in-line propagation of first-order diffraction at wavelengths of λ = 1300 - 2000 nm utilizing chalcogenide glass fibers.

Distributed Poloidal Magnetic Field Measurement in Tokamaks Using Polarization-Sensitive Reflectometric Fiber Optic Sensor.

Determination of the poloidal magnetic field distribution in tokamaks is of prime importance for the successful operation of tokamaks. In this paper, we propose a polarization-sensitive reflectometry-based optical fiber sensor for measuring the spatial distribution of the poloidal magnetic field in tokamaks. The measurement method exploits the Rayleigh backscattering and Faraday magneto-optic effect in optical fibers. The former is an intrinsic property of optical fibers and enables distributed polarization measurements, while the latter arises in the presence of a magnetic field parallel to the optical fiber axis and rotates the polarization state of the light. When an optical fiber is looped around a toroidal section of the vacuum vessel, the local polarization rotation of the light is proportional to the local poloidal magnetic field in the tokamak. The proposed method is discussed theoretically and experimentally using the results from JET. The obtained magnetic field measurement shows a good agreement with that of the internal discrete coils. A potential solution to recover the magnetic field data from the noise-affected region of the optical measurement is proposed and is demonstrated through simulations using the JET magnetic field configuration.

Integrated Manufacturing of Suspended and Aligned Nanofibrous Scaffold for Structural Maturation and Synchronous Contraction of HiPSC-Derived Cardiomyocytes.

Electrospun nanofiber constructs represent a promising alternative for mimicking the natural extracellular matrix in vitro and have significant potential for cardiac patch applications. While the effect of fiber orientation on the morphological structure of cardiomyocytes has been investigated, fibers only provide contact guidance without accounting for substrate stiffness due to their deposition on rigid substrates (e.g., glass or polystyrene). This paper introduces an in situ fabrication method for suspended and well aligned nanofibrous scaffolds via roller electrospinning, providing an anisotropic microenvironment with reduced stiffness for cardiac tissue engineering. A fiber surface modification strategy, utilizing oxygen plasma treatment combined with sodium dodecyl sulfate solution, was proposed to maintain the hydrophilicity of polycaprolactone (PCL) fibers, promoting cellular adhesion. Human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs), cultured on aligned fibers, exhibited an elongated morphology with extension along the fiber axis. In comparison to Petri dishes and suspended random fiber scaffolds, hiPSC-CMs on suspended aligned fiber scaffolds demonstrated enhanced sarcomere organization, spontaneous synchronous contraction, and gene expression indicative of maturation. This work demonstrates the suspended and aligned nano-fibrous scaffold provides a more realistic biomimetic environment for hiPSC-CMs, which promoted further research on the inducing effect of fiber scaffolds on hiPSC-CMs microstructure and gene-level expression.

Endospore pili: Flexible, stiff, and sticky nanofibers

Species belonging to the Bacillus cereus group form endospores (spores) whose surface is decorated with micrometers-long and nanometers-wide endospore appendages (Enas). The Enas have recently been shown to represent a completely novel class of Gram-positive pili. They exhibit remarkable structural properties making them extremely resilient to proteolytic digestion and solubilization. However, little is known about their functional and biophysical properties. In this work, we apply optical tweezers to manipulate and assess how wild-type and Ena-depleted mutant spores immobilize on a glass surface. Furthermore, we utilize optical tweezers to extend S-Ena fibers to measure their flexibility and tensile stiffness. Finally, by oscillating single spores, we examine how the exosporium and Enas affect spores’ hydrodynamic properties. Our results show that S-Enas (μm-long pili) are not as effective as L-Enas in immobilizing spores to glass surfaces but are involved in forming spore-to-spore connections, holding the spores together in a gel-like state. The measurements also show that S-Enas are flexible but tensile stiff fibers, which support structural data suggesting that the quaternary structure is composed of subunits arranged in a complex to produce a bendable fiber (helical turns can tilt against each other) with limited axial fiber extensibility. Finally, the results show that the hydrodynamic drag is 1.5 times higher for wild-type spores expressing S- and L-Enas compared with mutant spores expressing only L-Enas or “bald spores” lacking Ena, and 2 times higher compared with spores of the exosporium-deficient strain. This study unveils novel findings on the biophysics of S- and L-Enas, their role in spore aggregation, binding of spores to glass, and their mechanical behavior upon exposure to drag forces.

Structural Health Monitoring of Adhesively Bonded Pipe-to-Socket Joints by Integration of Polymer Optical Fibers and Their Load-Dependent Transmission Properties

Adhesively bonded pipe-to-socket joints are used in numerous industrial applications. One example is in the transport of media, e.g., in the gas industry or in structural joints for such sectors as construction, wind energy, and the vehicle industry. To monitor such load-transmitting bonded joints, this study investigates a method based on the integration of polymer optical fibers into the adhesive layer. Previous methods for monitoring the condition of pipes, such as acoustic or ultrasonic methods or the use of glass fiber optic-based sensors (FBG or OTDR), are very complex in methodology and require cost-intensive (opto-) electronic devices to generate and evaluate the sensor signals; they are therefore unsuitable for large-scale use. The method investigated in this paper is based on the measurement of integral optical transmission with a simple photodiode under increasing mechanical stress. When tried at coupon level (single-lap joint), the light coupling was varied to obtain a significant load-dependent sensor signal. Based on an angle-selective coupling of 30° to the fiber axis, a drop of 4% of the optically transmitted light power by a load of 8 N/mm2 can be detected for the adhesively bonded pipe-to-socket joint with the structural adhesive Scotch Weld DP810 (2C acrylate).