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Delamination is a prevalent type of damage in composite laminate structures. Its accumulation degrades structural performance and threatens the safety and integrity of aircraft. This study presents a method for the quantitative identification of delamination identification in composite materials, leveraging distributed optical fiber sensors and a model updating approach. Initially, a numerical analysis is performed to establish a parameterized finite element model of the composite plate. Then, this model subsequently generates a database of strain responses corresponding to damage of varying sizes and locations. The radial basis function neural network surrogate model is then constructed based on the numerical simulation results and strain responses captured from the distributed fiber optic sensors. Finally, a multi-island genetic algorithm is employed for global optimization to identify the size and location of the damage. The efficacy of the proposed method is validated through numerical examples and experiment studies, examining the correlations between damage location, damage size, and strain responses. The findings confirm that the model updating technique, in conjunction with distributed fiber optic sensors, can precisely identify delamination in composite structures. [ABSTRACT FROM AUTHOR]

In the context of the emerging Industry 4.0 paradigm, smart fabric sensors have been representing a novel addition to the textile industry. The proposed sensors utilize macro-bending techniques with varying fiber optic core sizes. The study involved the construction and testing of macro-bending sensors using single-mode (9 µm) and hetero-core (50-9-50 µm) fibers, configured into seven sinusoidal loops. The experiment was further extended to different types of elastic textiles. Spandex demonstrated superior linearity compared with jersey and rubber bands. The integration with the DOIT ESP32 DevKit facilitated real-time monitoring of respiratory rates. The results from the experiment indicated that the macro-bending sensor, fabricated using hetero-core optical fiber, exhibited superior sensitivity in comparison to the sensor assembled from single-mode optical fiber, with respective sensitivity values of 1.72 and 1.30 dB/cm. The designed sensors displayed closely aligned behavior during forward and reverse loading, indicating the reversibility of the fiber optic sensor. Given its simplistic design and low fabrication cost, the proposed sensor holds significant potential for practical applications. [ABSTRACT FROM AUTHOR]

Surface plasmon resonance (SPR) conventionally occurs at the interface of a thin metallic film and an external dielectric medium in fiber optics through core‐guided light. However, this work introduces theoretical and experimental evidence suggesting that the SPR in optical fibers can also be induced through light scattering from Au nanoparticles (NPs) on the thin metallic film, defined as nanoparticle‐induced SPR (NPI‐SPR). This method adheres to phase‐matching conditions between SPR dispersion curves and the wave vectors of scattered light from Au NPs. Experimentally, these conditions are met on an etched optical fiber, enabling direct interaction between light and immobilized Au NPs. Compared to SPR, NPI‐SPR exhibits stronger field intensity in the external region and wavelength tuning capabilities (750 to 1250 nm) by varying Au NP diameters (20 to 90 nm). NPI‐SPR demonstrates refractive index sensitivities of 4000 to 4416 nm per refractive index unit, nearly double those of typical SPR using the same optical fiber configuration sans Au NPs. Additionally, NPI‐SPR fiber configuration has demonstrated its applicability for developing biosensors, achieving a remarkable limit of detection of 0.004 nm for thrombin protein evaluation, a twenty‐fold enhancement compared to typical SPR. These findings underscore the intrinsic advantages of NPI‐SPR for sensing. [ABSTRACT FROM AUTHOR]

Advances in imaging tools have always been a pivotal driver for new discoveries in neuroscience. An ability to visualize neurons and subcellular structures deep within the brain of a freely behaving animal is integral to our understanding of the relationship between neural activity and higher cognitive functions. However, fast highresolution imaging is limited to sub-surface brain regions and generally requires head fixation of the animal under the microscope. Developing new approaches to address these challenges is critical. The last decades have seen rapid progress in minimally invasive endo-microscopy techniques based on bare optical fibers. A single multimode fiber can be used to penetrate deep into the brain without causing significant damage to the overlying structures and provide high-resolution imaging. Here, we discuss how the full potential of high-speed super-resolution fiber endoscopy can be realized by a holistic approach that combines fiber optics, light shaping, and advanced computational algorithms. The recent progress opens up new avenues for minimally invasive deep brain studies in freely behaving mice. [ABSTRACT FROM AUTHOR]

In nonlinear Schrödinger equations (NLSEs), the third-order generalized NLSE is a significant sculpture which is utilized for modeling ultrashort pulses in fiber optics. In this study, we obtained wave and soliton solutions by using new extended and modified Rational expansion method to get several types of soliton such as bright solitons, dark solitons, perodic solitons and traveling waves. In three-dimensional and two-dimensional plots, we present graphical representations in dissimilar structures of some solutions to understand the phenomena physically. The development and achievements of computing show the power and effectiveness of current technology. In addition, we are able to resolve various other high-order NLSEs with the assistance of effortless and effectual technique. [ABSTRACT FROM AUTHOR]

Photonic technologies have made enormous impacts on modern medicine, advancing disease diagnostics and treatments as well as health monitoring. A long‐standing challenge in the use of light and its widespread effects in photomedicine is the finite penetration of light in tissues. However, judiciously engineered optical fibers helped overcome this challenge and advance light delivery to deep tissues with spatial precision and desired accessibility. In recent years, the development of photonic technologies including optical biomaterials, fiber functionalization, and biomedical device innovations has greatly expanded the scope of light‐based healthcare. Here, the fundamentals and materials of fiber optics to endow themselves with biocompatibility, flexibility, and diverse functionalities required for long‐term implantation are overviewed. The design strategies of lab‐on‐fiber techniques, operation requirements to construct fiber optic sensors, and their health monitoring applications as wearable and implantable devices are presented. The use of fiber optics in major light‐based therapeutic modalities including optogenetics, photodynamic therapy, photobiomodulation, photochemical cross–linking, and photothermal therapy is illustrated to enhance their effectiveness, specificity, and feasibility. In short, a comprehensive review is provided on the fiber optic techniques and the latest photonic devices, which are envisioned to evolve photomedicine in clinical and point‐of‐care practices. [ABSTRACT FROM AUTHOR]

This paper explores the need for establishing a microwave link between Bahir Dar and Woretta as an alternative communication solution to the existing optical fiber infrastructure. Microwave links offer an effective way to overcome challenges posed by rugged terrains and unfavorable environmental conditions that hinder the deployment of fiber optics. As Woretta emerges as a key economic and investment hub within the Amhara Region, demand for reliable and efficient communication is expected to grow significantly. The study encompasses various aspects of planning and designing the microwave link, including site surveys, consideration of fade margins, frequency planning, link budget calculations, and assessing the feasibility and reliability of the proposed link. The paper employs LINKPlanner 5.4.1 software to simulate and validate the results. Due to terrain constraints, a direct link between Bahir Dar and Woretta is not feasible. Instead, a two-hop link is proposed, involving transmission from Bahir Dar to Zege, and then from Zege to Woretta. This alternative configuration ensures optimal connectivity while addressing the terrain limitations. By presenting a comprehensive analysis and simulation of the microwave link, this paper provides valuable insights into the planning and implementation of a robust communication infrastructure. The proposed microwave link will offer a reliable and efficient alternative to the existing optical fiber network, ensuring uninterrupted connectivity to support the region's growth and development. [ABSTRACT FROM AUTHOR]

Optical wireless communication systems employing free-space optical (FSO) links utilize modulated lasers to transmit information. FSO–fiber optic (FO) link provides an alternative possible way in scenarios where infrastructures employing optical fibers are widely destroyed due to disasters or when difficulties are faced during the installation of FO links. Furthermore, the link is integrated with decision-making ability. To encounter the distortions in the received signal carrier-suppressed return-to-zero modulation format has been used. FSO–FO hybrid link has been compared with simple FSO channel. The terrestrial links depend strongly on weather conditions as optical beams propagate through the atmosphere. Atmospheric attenuation could affect the FSO channel and has been considered to analyze the performance of the designed system. [ABSTRACT FROM AUTHOR]

Distributed Acoustic Sensing (DAS) is becoming a powerful tool for earthquake monitoring, providing continuous strain‐rate records of seismic events along fiber optic cables. However, the use of standard seismological techniques for earthquake source characterization requires the conversion of data in ground motion quantities. In this study we provide a new formulation for far‐field strain radiation emitted by a seismic rupture, which allows to directly analyze DAS data in their native physical quantity. This formulation naturally accounts for the complex directional sensitivity of the fiber to body waves and to the shallow layering beneath the cable. In this domain, we show that the spectral amplitude of the strain integral is related to the Fourier transform of the source time function, and its modeling allows to determine the source parameters. We demonstrate the validity of the technique on two case‐studies, where source parameters are consistent with estimates from standard seismic instruments in magnitude range 2.0–4.3. When analyzing events from a 1‐month DAS survey in Chile, moment‐corner frequency distribution shows scale invariant stress drop estimates, with an average of Δσ = (0.8 ± 0.6) MPa. Analysis of DAS data acquired in the Southern Apennines shows a dominance of the local attenuation that masks the effective corner frequency of the events. After estimating the local attenuation coefficient, we were able to retrieve the corner frequencies for the largest magnitude events in the catalog. Overall, this approach shows the capability of DAS technology to depict the characteristic scales of seismic sources and the released moment. Plain Language Summary: A new formulation for far‐field strain radiation from seismic ruptures is derived, leading to a direct interpretation of Distributed Acoustic Sensing (DAS) data to retrieve source properties (seismic moment and source size), via a spectral modeling. This approach is validated on real data recorded in two different tectonic environments, the Chilean margin and the southern Apennines, in Italy. Despite the unique directional sensitivity and peculiar signal characteristics, we demonstrated the high potential of DAS systems in characterizing the seismic ruptures over different space scales, with accuracy increased by redundancy of information from the very‐high spatial resolution in the recording of seismic waves. Key Points: A theoretical description of strain far field radiation from a seismic rupture is introducedSource parameters were evaluated from strain data for earthquakes in magnitude range 2.0–4.3Distributed Acoustic Sensing allows for investigation of source parameters and site effects with fine spatial resolution [ABSTRACT FROM AUTHOR]

Heavy metals such as lead are gradually pervading aquatic bodies in an alarming manner. Abundance beyond a permissible level makes the aquatic bodies toxic. As such, there is a requirement of effective sensing schemes toward monitoring of the concentration of these polluting ions. Accordingly, we present here a novel photonic sensor. Using Arduino Microcontroller, which makes the device portable and usable for remote sensing, an analyte in the form of lead ion is detected. The photonic sensor is found to be immune to interfering, thus rendering specificity for lead ion. [ABSTRACT FROM AUTHOR]

This article focuses to extract the optical solitons in fiber optics modeled by (1 + 1)-dimensional coupled nonlinear Schrödinger equation (NLSE) by the assistance of truncated M-fractional derivative. Circularly polarized waves in fiber optics are described by the studied equation. The NLSEs have attracted greater attention due to their ability to effectively elucidate a diverse array of intricate physical phenomena and their capacity to exhibit deeper dynamical patterns through localised wave solutions. The solutions are obtained using the modified Sardar sub-equation method (MSSEM), which is a recently developed integration technique. Various types of optical pulses, including bright, dark, combo, and singular soliton solutions, are obtained. Considering appropriate parameters, a variety of graph shapes are sketched to describe the graphical presentation of the calculated outcomes. The findings indicate that the chosen technique is effective in improving nonlinear dynamical behaviour. We anticipate that many engineers who use engineering models will find this study to be of interest. The results validate the simplicity, effectiveness, and universality of the selected computational approach, even when applied to complex systems. [ABSTRACT FROM AUTHOR]

In this article, we investigate fifth-order variable coefficient nonlinear SchrÖdinger equation, which govern optical pulse in fiber optics and obtain soliton and breather solutions by applying Darboux transformation. Soliton and breather are responsible for data transmission over the long distance without loss of power. In optical fibers, control soliton and breather interactions have important application in signal processing and transmission. In solutions, With different values of coefficients of dispersion we obtain parabolic, cubic and periodical oscillating soliton. By controlling spectral parameter λ, we obtain different types of interactions like head on, overtaking and parallel on soliton. The effects of coefficients of dispersion and spectral parameter λ on the pattern of breather also presented. [ABSTRACT FROM AUTHOR]

In this work, we realised the soliton solutions of nonlinear Schrödinger equation (NLSE) that arise from optical fibers, we considered the modified Sardar sub-equation method (MSSEM) to find solitary solutions analytically. The stability of the retrieved soliton solutions realised from the NLSE are investigated. We demonstrate the soliton solutions that are stable and can last for a very long time without losing its form or energy under specific circumstances and those soliton solutions that are unstable. The MSSEM is a frequently employed technique in research for addressing specific mathematical modeling or physical phenomena problems. Its selection in this specific study might stem from its proven efficacy in handling the particular problem under investigation. The decision to utilize MSSEM could be driven by several considerations, including its precision, computationally efficient, effectiveness, greater accuracy and capability to manage intricate systems. Finally, our method offers greater flexibility in modeling various physical phenomena, which makes it particularly useful in applications in diverse fields such as quantum mechanics and nonlinear optics. The findings have ramifications for the architecture of optical fiber communications and offer significant new insights into the behavior of solitons in optical systems. The NLSE has proven to be an effective tool for understanding wave behavior in fiber optics. Its applications have helped engineers and scientists optimize the design of optical fibers and predict the behavior of various conditions. Moreover, our study provides insights into the fundamental properties of solitary solutions in the NLSEs and their practical implications in physical systems. [ABSTRACT FROM AUTHOR]

In this article, the nonlinear cubic-quartic Fokas-Lenells equation with third and fourth order dispersion is theoretically investigated. The considered equation is a modified form of Fokas–Lenells equation and provides a useful description of optical pulse propagation through optical fibers in many problems of nonlinear optics. The application of modified auxiliary equation approach and extended (G ′ G 2) -expansion has allowed the extraction of precise closed form solutions to the equation. The obtained solution expressions are in terms of trigonometric functions, hyperbolic functions and rational functions. The graphical properties of the developed solutions are also observed in this process by plotting 3D surface graphs, contour plots and line graphs for different values of parameters. The considered model is examined for the first time in this work using the proposed techniques and novel results are observed. The reported results include a variety of dynamical behavior for the considered equation which will be helpful in further explorations to understand wave propagation through optical fibers and nonlinear optics. The constructed bright solitons are particularly beneficial in data communication through fibers in nonlinear optics. [ABSTRACT FROM AUTHOR]

Softphotonics has emerged as a new discipline that utilizes soft matter (i.e., liquids, gels, bio‐materials) as waveguide materials with versatile functionalities. The flexible properties of soft matter show great potential for further exploiting nonlinear in‐fiber phenomena to gain more insights into their fundamental dynamics and to inspire a new generation of broadband optical light sources and signal processors that are adaptable, reconfigurable, and biocompatible. In particular, incorporating solvents with extraordinary temperature sensitivity, miscibility, and nonlinearity into optical fibers has spawned a series of inventions and fundamental scientific findings over the last decades. This review highlights the current state of development of nonlinear photonics in liquid‐filled fibers. The current state of knowledge in the linear and nonlinear material properties of the most prominent solvents (CS2, CCl4, C2Cl4, benzene and its derivatives) are revisited, and recent advances in nonlinear liquid‐core fiber optics, including a special highlight on phenomena that are unique to liquids, such as modified solitary states and local dispersion control are summarized. Finally, the leading scientific challenges for advancing the field, which highlights liquid‐core fibers as a rich platform for science and technology, are discussed. [ABSTRACT FROM AUTHOR]

Fiber-optic sensing has established itself as an innovative and versatile measurement technology for various physical parameters, such as temperature. Moreover, particular properties of optical fibers, in some cases, make fiber-optic sensing only suitable choice due to operation conditions, precision and accuracy, possibility of remote operation. In this paper we present the simple fiber optic temperature sensor system that utilizes reflective Bragg element as a sensing head. The main advantage of the proposed approach relies on the use of widely available low-cost telecommunication devices, such as a DFB laser as a light source and commonly used fiber optics components. Another advantage of the sensor is measurement technique that doesn’t require optical spectrometer or other precise optical measurements such as interferometry. It is shown that by implementing various Bragg structures for the sensing element it is possible to alter optical response thus achieving required characteristics of the sensor. Calculations for Bragg structures are presented for both narrow range sensor suitable for medical use and wide range temperature sensor with ΔT ~ 200°C. In addition, this paper provides brief review of commonly used fiberoptic temperature sensing techniques, their advantages and application. [ABSTRACT FROM AUTHOR]

This research article explores the potential of optical fibers as sensors, highlighting their ability to measure various parameters such as temperature, pressure, stress, and radiation dose. The study focuses on investigating the material compatibility of optical fibers in challenging sensing environments like Gen II/II+ and advance nuclear reactors, as well as concentrated solar power (CSP) plants. Material compatibility tests were conducted to determine the feasibility of using fluorine and germanium optical fiber sensors in these environments. The study found that raw fibers were corrosion-resistant to lead bismuth eutectic at 600 °C, regardless of the coating. In molten salt environments, raw fibers were incompatible with FLiNaK but showed corrosion resistance to MgCl₂-NaCl-KCl. However, the survivability of raw fiber optics improved with a gold coating in FLiNaK. Raw fiber optics were found to be incompatible in high-temperature steam at 1200 °C and in a pressurized water reactor (PWR) at 300 °C. [ABSTRACT FROM AUTHOR]

In this study, generalized higher-order nonlinear Schrödinger equation is under consideration analytically. This equation is used in the field of slowly varying envelope of the electric field in the optical fiber with self-phase modulation, third-order dispersion, self-steepening and stimulated Raman scattering. For the sake of optical solitons and other solutions, we use two methods such as generalized exponential rational function (GERFM) and Sardar subequation method (SSEM). The solutions are gained in different forms such as bright, dark, singular, combo solitons, as well as hyperbolic, trigonometric and rational solutions. Some of the acquired wave solutions are characterized graphically in 3D, contour forms and 2D shapes to illustrate the dynamical behavior. A comparable analysis of this study with the available consequences in literature confirms the innovation and assortment of present accomplished wave solutions and hence enhances the great performance of the employed techniques. The offered method can be utilized to assist complicated models applicable to a wide variety of physical situations. We hope that a wide spectrum of engineering model professionals will find this study to be beneficial. [ABSTRACT FROM AUTHOR]

This article focuses on securing distinct optical solitons to optical fiber with the coupled nonlinear Schrödinger equation. The examined equation is analyzed with the aid of conformable space–time fractional and is known to have a significant role in the propagation of pulses through a two-mode optical fiber and the soliton wavelength division multiplexing. The fractional nonlinear partial differential equations have garnered increased interest since they may be utilized to explain a wide range of complicated physical phenomena and have more dynamic structures of localized wave solutions. New extended direct algebraic method, a relatively recent integration tool, is used to obtain the solutions. The diverse pulses as bright, dark, combo, and singular soliton solutions have been extracted. In addition to aiding in the clarification of fractional nonlinear partial differential equations, the employed method provides previously extracted solutions and extracts new exact solutions. Given the correct parameter values, numerous graph forms are sketched to provide information on the visual presentation of the obtained findings. The achieved solutions are to be attractive to researchers for understanding the complexity of the considered model. The findings of this research validate the effectiveness of the proposed method for increasing nonlinear dynamical behavior. It is anticipated that, the research will be of interest to all engineers who work with engineering models. Results demonstrate the efficacy, simplicity, and generalizability of the selected computational method. [ABSTRACT FROM AUTHOR]

Picosecond laser ablation has recently emerged as a minimally invasive alternative to conventional surgical resection of early tumors, offering high precision and limited thermal damage to surrounding tissue. Potential clinical application routes include deployment through the working channels of endoscopes or needle bores, which require the delivery of ultrashort high energy pulses through flexible optical fibers with focusing optics at the distal end. The manufacture of distal end optical systems for fiber ablation is challenging, inhibiting translation toward clinical applications. Here, we present a miniature fiber-coupled ablation probe developed using ultrafast laser inscription and chemical etching, employing a hollow-core fiber for pulse delivery. Its design, fabrication, and characterization are detailed, along with a feasibility demonstration for the ablation of stainless steel and chicken tissue. [ABSTRACT FROM AUTHOR]

The purpose of this work is the examine the three-waves, double exponential, homoclinic breather, and periodic cross kink-soliton solutions for a third-order fractional nonlinear Schrödinger equation (3-FNLS). This model which is vital in fiber optics, explains the propagation of light in optical fibers when ultra-short pulses are produced. We define the model in terms of the conformable time fractional derivative operator so that the model could give a better description of the physical aspect. By picking the activation function in Hirota bilinear form, as the hyperbolic, trigonometric and exponential function along with suitable dispose of parameters, we acquire the three-waves, double exponential, homoclinic breather, and periodic cross kink-soliton auspiciously. Additionally, we have elucidated some three-dimensional and contour portraits to foresee the wave dynamics. These acquired new solutions that do not exist in the literature include some free constants and thereby can be significant to describe variety in qualitative aspects of wave phenomena. At last, we also check the stability of the governing model. By executing the modulation instability analysis, we scrutinize the stability analysis of the yielded exact solutions and the movement role of the waves. [ABSTRACT FROM AUTHOR]

In this paper, we discuss the propagation of optical pulses in the nonlinear optical fibers. The generalized higher-order nonlinear Schrödinger equation (NLSE) is under consideration as a governing model. The studied model is composed of group-velocity dispersion, self-phase modulation, third-order dispersion, self-steepening and stimulated Raman scattering. Researchers have been studying a wide range of natural phenomena in depth, and nonlinear science has gradually become a part of people's consciousness. We have extracted the optical pulses in different forms like bright, dark, singular and combined solitons by assistance of recently developed integration tool, namely the new extended direct algebraic method (NEDAM). Moreover, the solutions for the hyperbolic, periodic and trigonometric functions are retrieved. Using proper parameters in numerical simulations and physical explanations, it is possible to demonstrate the importance of the findings. It is proposed that the offered method can be utilized to support nonlinear dynamical models applicable to a wide variety of physical situations. We hope that a wide spectrum of engineering model professionals will find this study to be beneficial. [ABSTRACT FROM AUTHOR]

Diffuse reflectance spectroscopy (DRS) has proven to be a powerful, reliable, and non-invasive optical method for characterizing a specimen. Nevertheless, these methods are based on a rudimentary interpretation of the spectral response and can be irrelevant to understanding 3D structures. In this work, we proposed adding optical modalities into a customized handheld probe head in order to increase the number of parameters in DRS acquired from the light/matter interaction. It consists of (1) placing the sample in a reflectance manual rotation stage to collect spectral backscattered angularly resolved light and (2) illuminating it with two sequential linear polarization orientations. We demonstrate that this innovative approach leads to a compact instrument, capable of performing fast polarization-resolved spectroscopic analysis. Due to the significant amount of data available with this technique in a short time, we observe sensitive quantitative discrimination between two types of biological tissue provided by a raw rabbit leg. We believe that this technique can pave the way for rapid meat quality check or biomedical diagnosis of pathological tissues in situ at an early stage. [ABSTRACT FROM AUTHOR]

It is known that the growth of the orbital part of the angular momentum of the fundamental air core mode of the negative curvature hollow-core fibers (NCHCFs) with circular polarization occurs at the edge of the transmission bands due to the spin–orbit interaction. In this paper, we consider the resonant behavior of orbital angular momentum (OAM) for a linearly polarized fundamental air core mode in straight and bent NCHCF. The resonant growth of OAM is associated with coupling between the linear polarized fundamental air core mode and the cladding capillary wall modes. The coupling between the modes arises due to crossing and anti-crossing. This OAM growth can be explained by a complex interaction of energy fluxes of the coupled modes under crossing. This phenomenon may be useful for a deeper understanding of the processes arising from mode coupling in fiber optics and nanophotonics, as well as for generating and transmitting OAM modes in micro-structured optical fibers. [ABSTRACT FROM AUTHOR]

While optical fibers display excellent performances in the infrared, visible and ultraviolet ranges remain poorly addressed by them. Obtaining better fibers for the short-wavelength range has been restricted, in all fiber optics, by scattering processes. In hollow-core fibers, the scattering loss arises from the core roughness and represents the limiting factor for loss reduction regardless of the cladding confinement power. Here, we report on the reduction of the core surface roughness of hollow-core fibers by modifying their fabrication technique. The effect of the modified process has been quantified and the results showed a root-mean-square surface roughness reduction from 0.40 to 0.15 nm. The improvement in the core surface entailed fibers with ultralow loss at short wavelengths. The results reveal this approach as a promising path for the development of hollow-core fibers with loss that can potentially be orders of magnitude lower than the ones achievable with silica-core counterparts. In all fiber optics, loss in the visible and UV is restricted by scattering. By improving the core roughness of hollow-core fibers, record attenuation values at short-wavelengths were achieved, opening exciting prospects in visible and UV-photonics. [ABSTRACT FROM AUTHOR]

Macrobends are optical fiber structures suitable for detecting motion changes. This structure has been developed using single-mode fibers and a combination of single-mode and multimode fibers called hetero-core. In this study, a new macrobending structure was designed and developed by adding a nano-ZnO element to the fiber optic core based on Revolution 4.0. The addition of nanomaterial elements involves an etching process that uses harmful chemicals or high-cost laser technology. Therefore, hetero-core was applied in this study to replace the etching process. The ZnO-coated fiber optics with 10 (ZnO1), 20 (ZnO2), and 30 (ZnO3) times of dip coating were developed using the dip-coating method and characterized using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) spectroscopy. Sensitivity measurement was conducted with glued optical fiber in the form of bending using a tape with a bending dimension of 2.5 cm × 1.5 cm and a wavelength of 1,550 nm. Morphological characterization using SEM proves that nanoparticles are attached to the optical fiber, and the EDX characterization confirms that the nanoparticles are ZnO elements. Optical fiber sensor sensitivity using core sizes 9, 50–9–50, 50–9–50 (ZnO1), 50–9–50 (ZnO2), and 50–9–50 (ZnO3) achieved sensitivity values of 0.91, 1.61, 2.98, 3.34, and 3.51, respectively. This study successfully produced ZnO-coated optical fiber sensors with a hetero-core structure without performing the etching process and successfully increased the sensitivity of the sensors. [ABSTRACT FROM AUTHOR]

The detection of methane, a strong greenhouse gas, has increased in importance due to rising emissions, which partly originate from unreported and undetected leaks in oil and gas fields. The gas emitted by these leaks could be detected using an optical fiber-based photoacoustic sensor called PAS-WRAP. Here, we investigate the potential of silicon-based membranes as more sensitive microphones in the PAS-WRAP concept. Toward this goal, we built a setup with which the frequency response of the membranes was interrogated by an optical fiber. Multiple mounting mechanisms were tested by adapting commercial interferometry systems (OP1550, ZonaSens, Optics11 B.V.) to our case. Finally, methane detection was attempted using a silicon nitride membrane as a sensor. Our findings show a quality factor of 2.4 at 46 kHz and 33.6 at 168 kHz for a thin silicon nitride membrane. This membrane had a frequency response with a signal-to-background ratio of 1 ± 0.7 at 44 kHz when tested in a vacuum chamber with 4% methane at 0.94 bar. The signal-to-background ratio was not significant for methane detection; however, we believe that the methods and experimental procedures that we used in this work can provide a useful reference for future research into gas trace detection with optical fiber-based photoacoustic spectroscopy. [ABSTRACT FROM AUTHOR]

Optical fiber has been widely used as a transmission media for data communication networks for many years. However, considering the broad advantages offered by fiber optics, research projects in this area go beyond data transmission; among the topics that can be found in this field are photonic sensors. Some characteristics decisive now in promoting the research of photonic sensors are the unique advantages that they offer, such as immunity to electromagnetic interference, its low weight and volume, and long lifetime, among others. This paper presents the design and analysis of a distributed optical sensors network using the largest network topology in the country, called the National Optical Fiber Project (PNFO). [ABSTRACT FROM AUTHOR]

The improved perturbed nonlinear Schrödinger equation with parabolic law nonlinearity (IPNLSE-PLN) will be studied with the assistance of Hirota bilinear method (HBM) and sort out some new solitons and their interactions for our governing model. These interactions play a dominant role in the area of optical fiber and nonlinear optics. We will obtain butterfly, S and W-shaped, parabolic, dark and other solitary wave solutions (SWS) for our governing model. We will also apply sine-Gordon expansion (SGE) technique to our model and find some new SWSs. [ABSTRACT FROM AUTHOR]

This paper investigates the optical solitons to the Biswas–Arshed equation (BAE) with third-order dispersion and self-steepening coefficients that communicate pulse propagation in fiber optics. The equation is considered where self-phase modulation is negligibly small and hence removed. Under different constraint conditions, the extended Fan sub-equation method (EFSEM) is used to derive the different kinds of solutions in the forms of bright, dark, singular, complex and combined solitons. In addition, Jacobi elliptic function (JEF) periodic, hyperbolic-type solutions are secured. This technique is useful for solving NLPDEs because it combines the results of numerous operations to provide previously extracted solutions as well as fresh solutions. While describing the physical representation of particular solutions, we also plot 3D, and 2D graphs by picking appropriate values for the solutions' related parameters. On the basis of a comparison of our results with well-known ones, the study indicates that our answers are innovative. Nonlinear dynamical behavior of a particular system can be improved and the methodology applied can be shown to be effective by these findings. Engineering modelers will greatly benefit from this study, according to our opinion. Based on the results obtained, the computational method adopted is efficient and direct, as well as succinct and can be applied to complex systems. [ABSTRACT FROM AUTHOR]

The generation of tailored light fields with spatially controlled intensity and phase distribution is essential in many areas of science and application, while creating such patterns remotely has recently defined a key challenge. Here, we present a fiber-compatible concept for the remote generation of complex multi-foci three-dimensional intensity patterns with adjusted relative phases between individual foci. By extending the well-known Huygens principle, we demonstrate, in simulations and experiments, that our interference-based approach enables controlling of both intensity and phase of individual focal points in an array of spots distributed in all three spatial directions. Holograms were implemented using 3D nano-printing on planar substrates and optical fibers, showing excellent agreement between design and implemented structures. In addition to planar substrates, holograms were also generated on modified single-mode fibers, creating intensity distributions consisting of about 200 individual foci distributed over multiple image planes. The presented scheme yields an innovative pathway for phase-controlled 3D digital holography over remote distances, yielding an enormous potential application in fields such as quantum technology, life sciences, bioanalytics and telecommunications. Overall, all fields requiring precise excitation of higher-order optical resonances, including nanophotonics, fiber optics and waveguide technology, will benefit from the concept. [ABSTRACT FROM AUTHOR]

Laser surgery has accumulated decades of clinical experience, showing its impact on medicine, particularly in the field of urology. During that time, laser surgical applications were dominated by Nd:YAG lasers, because of their ability to be coupled to optical fibers. More recently, solid state and fiber-based lasers have burst into the scene. These are capable of emitting in the mid-infrared range of the spectrum thanks to elements such as Ho, Tm and Er, whose strong absorption by tissues or water, combined with high efficiency and greater robustness, have made them the most promising candidates for urology. Here we present the most employed lasers in urology, emphasizing the holmium ones and their wide applications for more than 20 years, and the thulium fiber lasers, because of their outstanding characteristics and strategic importance. [ABSTRACT FROM AUTHOR]

Fiber-optic network infrastructures are crucial for the transmission of data over long and short distances. Fiber optics are also preferred for the infrastructure of in-building data communications. In this study, we use polarization analysis to ensure the security of the optical fiber/cables of the physical layer. This method exploits the changes induced by mechanical vibrations to polarization states, which can be easily detected using a polarization beam splitter and a balancing photodetector. We use machine learning to classify selected events that violate the safety of the physical layer, such as manipulation or temporary disconnection of connectors. The results show the resting state can be accurately distinguished from selected security breaches for a fiber route subjected to environmental disturbances, where individual events can be classified with nearly 99% accuracy. [ABSTRACT FROM AUTHOR]

We have applied the measurement reduction technique for the ghost imaging (GI) in fiber optics systems. Ghost images have been reconstructed by numerical simulation of the complete cycle of GI in the basic setup of a multimode fiber endoscope beginning from the propagation of randomly modulated light through a multimode fiber and ending by GI calculation using numerical methods of single-pixel visualization. We have used prior information on the investigated object to obtain high-quality reconstructed ghost images. It is shown that for the number of used patterns of illumination of the object that is much smaller than the number of pixels of the image being reconstructed, the object reconstruction error can be reduced despite the limitation imposed on the number of modes propagating through the optical fiber and forming incoherent radiation. For comparison, we have used several versions of the compressed sensing method and the traditional correlation method. It is demonstrated that the proposed version of the measurement reduction technique applied to multimode fibers shows comparable and often even better results than the traditional correlation method and the compressed sensing method. [ABSTRACT FROM AUTHOR]

• The DFO is applied to monitor the circumferential joint shear tests of segments with positioning tenons. • The circumferential shear failure patterns of segments with positioning tenons are presented. • The damage characteristics of the positioning tenon and its interaction with the segments are revealed. • The main crack shear coefficient is proposed for evaluating residual shear performance. Positioning tenons have been used in more and more subway projects to improve segment assembly performance and to limit the occurrence of common problems between segments. The joints are the weak parts of the segment connection and are often damaged during construction. However, there are limited studies on the joints of segments with positioning tenons, and their damage characteristics have yet to be investigated. In this study, circumferential joint shear damage in segments with positioning tenons is studied and the evolution of the distributed damage is monitored by distributed fiber optics. First of all, the shear performance of segments with positioning tenons is investigated under different axial forces. Particularly, the damage distribution and development of segments subjected to the extrusion of the positioning tenons are analyzed through the strain signals and the macroscopic cracks during the shearing process. Furthermore, the changes in the strain signals of the distributed fiber before shear failure are analyzed. Based on the above study, the failure patterns of the inner surfaces and circumferential joint surfaces of segments with grooves are revealed. The interaction between the positioning tenons and the segments is analyzed, and the damage characteristics of the tenons are obtained. Finally, the main crack shear coefficient is proposed to evaluate the residual shear performance of segments when the macroscopic main crack occurs on the inner surface. This study aims to reveal the interaction between positioning tenons and segments and to promote the application of positioning tenons in subways. Further, it lays the foundation for optimizing the flexible joints of segments in subways and contributes to the safe construction of subway tunnels. [ABSTRACT FROM AUTHOR]

• Optic fibers face durability challenges due to elevated oxidative stress. • Fabrication optimization via FDM 3D printing with PETG filament. • Immersion in hydrogen peroxide solution shows negligible morphological degradation. • Optical loss remains low at 0.024 dB/cm after 3 weeks in 45 mM hydrogen peroxide. • Young Modulus of all immersed fiber remains in the filament's range of 1898.7 ± 98.5 Mpa. • Biocompatibility testing indicates long-term suitability: 88% cell viability after one day, 70% after one week. Wound dressing integrated with optic fiber has been fabricated to overcome the limitation of conventional wound monitoring method which relies heavily on visual inspection. Nevertheless, wounds pose a challenge due to elevated oxidative stress, raising concerns about the durability and stability of optical fibers. With the advancement of 3D printing technology in the optical fiber field, this study employs the Fused Deposition Method (FDM) technique using Polyethylene terephthalate glycol (PETG) filament with different nozzle temperature for fabricating optical fiber directly from the filament via direct extrusion from the nozzle. The study will follow with immersing the fiber optic in wound mimicked oxidative stress prepared using different concentrations of hydrogen peroxide which 0.1 mM, 0.175 mM, and 0.25 mM for acute wounds while 15 mM, 30 mM and 45 mM for chronic wounds. The fabricated fiber optics are characterized by the optical properties for the attenuation and transmission spectra, morphology, structural analysis and cytotoxicity. The fabricated optical fibers are immersed in the solutions for up to three weeks and characterized for their stability in oxidative stress. The results show that printing 0.8 mm PETG fiber at the standard manufacturing temperature of 230°C- 240°C results in poor quality in which formation of bubbles can be observed along the fiber while reducing the temperature to 210°C has optimized the printing quality with no presence of bubble and produce smooth surface. Immersing the printed PETG optical fiber in different hydrogen peroxide up to three weeks at different concentration did not affect the morphology where no degradation signs such as pits or cracks can be observed. The optical loss after immersion in 45 mM at 3 weeks also remains low at 0.024 dB/cm comparable to 0.016 dB/cm for non-immersed fiber. The transmission spectra, however, show a reduction in the intensity from 15,000 intensity counts to 12000. Additionally, the Young's Modulus of all the immersed fibers remains consistently within the manufacturer's specified range of 1898.7 ± 98.5 MPa. This indicates that regardless of the concentration of the hydrogen peroxide the mechanical properties of the fiber are not affected. However, loss of peaks is observed in the FTIR spectra which may indicates the initiation of degradation. The cell viability confirms the biocompatibility of the fiber with approximately 88% and 70% viable cells after one day and one week analysis, respectively indicating its suitability for wound monitoring applications [ABSTRACT FROM AUTHOR]

The non-linear random Schrodinger equation via geometric distribution and exponential distribution is considered. We carry out the unified solver technique to obtain some new random solutions. The statistical distributions are utilized to show the dispersion random input. The reported random solutions are so important in fiber optics and their applications. The expectation for the random solutions are drawn to show the behaviour of solutions. [ABSTRACT FROM AUTHOR]

Partial discharge (PD) is a common defect to determine the quality of high-voltage power equipment insulation systems. Localization of PD is very important for equipment maintenance and risk assessment. A localization algorithm of received signal strength (RSS) using demodulating PD optical signal is proposed. This is based on the optical effects caused by PD, which influence the optical signal that is transmitted through an optical fiber sensor placed inside the equipment. Compared with plastic fluorescent fiber, SiO2 cladding YAP:Ce crystal core fluorescent fiber (SYCF) with high luminous efficiency, low loss, and strong anti-electromagnetic interference capability is selected as the sensing unit to detect the received optical signal strength of PD, through the all-fiber optic sensing system to achieve the PD location in 3-D space. Based on the optical RSS localization method, the range of localization deviation of PD under 37-kV applied voltage is measured and studied. The average localization deviation and the error are 6.9 cm and 7.4%, respectively. Comparing the optical signal location method based on RSS with other methods of PD localization, the advantages and accuracy of the optical location method proposed in this article are outstanding. Therefore, the all-fiber system with SYCF via optical signal has a wide application prospect in the spatial localization of PD. [ABSTRACT FROM AUTHOR]

To quantify the diffusion range of slurry in grouting engineering, an active heating optical fiber (AHFO) monitoring method is proposed. The AHFO is arranged on the coal seam floor. The temperature is taken as the monitoring parameter to monitor the diffusion range and state of slurry in the injected medium. Considering the time-varying characteristics of slurry rheological parameters, the theoretical calculation formula of spherical diffusion radius based on the power-law fluid is deduced. The relationship between the void ratio and grouting diffusion radius is discussed. Considering the influence of the seepage effect, the "water cement ratio change matrix" in the process of mud seepage is derived, and the influence of the space–time change of the slurry water cement ratio on the temperature gradient of the injected medium is studied. According to the factors affecting grouting diffusion, four groups of small three-dimensional simulation tests and one large three-dimensional grouting test are designed to verify the feasibility of the proposed method. The results show that the relative error of the AHFO monitoring radius is between 3.00 and 14.67%, based on the actual diffusion radius. In the large-scale three-dimensional grouting test, the data from AHFO is used to generate the two-dimensional surface of the grouting diffusion form, and the grouting diffusion range is asymmetric oval. Compared with the theoretical calculation results, the maximum relative error of grouting diffusion radius is 9.6%, and AHFO shows prediction accuracy. With the decrease in the water-cement ratio of slurry, the temperature gradient of the injection medium monitored by AHFO increases, showing an obvious space–time effect. The application of AHFO in the grouting simulation test can effectively analyze slurry diffusion in the injected medium. [ABSTRACT FROM AUTHOR]

In material-processing fiber lasers, the resonator in the closed box produces the laser radiation. Even with the same resonator, the diameter of the laser beam transporting fiber optics and the properties of the optical elements in the laser focusing head decide the cross-section of the focused laser beam used for machining. If we summarize the formulas in different sources in the literature, we can predict the effect of each optical element: what will happen if we choose another focusing lens, put a beam expander in the system, set on the beam expander how many times the laser beam expands. The other important point is that if we want to repeat an experiment or start a production process based on a scientific publication, then in addition to the resonator, it would be good to know the data of the optical elements in the focusing head, which is usually incomplete in the presented articles, but we can determine them approximately using the four formulas listed in the article. [ABSTRACT FROM AUTHOR]

Distributed optical fiber sensing is a unique technology that offers unprecedented advantages and performance, especially in those experimental fields where requirements such as high spatial resolution, the large spatial extension of the monitored area, and the harshness of the environment limit the applicability of standard sensors. In this paper, we focus on one of the scattering mechanisms, which take place in fibers, upon which distributed sensing may rely, i.e., the Rayleigh scattering. One of the main advantages of Rayleigh scattering is its higher efficiency, which leads to higher SNR in the measurement; this enables measurements on long ranges, higher spatial resolution, and, most importantly, relatively high measurement rates. The first part of the paper describes a comprehensive theoretical model of Rayleigh scattering, accounting for both multimode propagation and double scattering. The second part reviews the main application of this class of sensors. [ABSTRACT FROM AUTHOR]

Carbon fibers and resin used in manufacturing carbon fiber-reinforced plastic composite structures flow before the resin solidifies, resulting in disrupted fiber orientation and non-uniform thickness. This process, known as consolidation, is critical for the quality of the composite structure, but no technology exists to measure the deformation in situ. This study proposes a strip-type embeddable shape sensor based on fiber optics for in situ monitoring of consolidation deformation. The sensor consists of a thin, flexible sheet with optical fibers embedded in the upper and lower surfaces of the sheet, and it can monitor out-of-plane bending deformation in composite materials during consolidation. Finite element analysis and experiments are used to evaluate the basic performance of the shape sensor before it is applied to composite gap/lap monitoring. For the first time, the relaxation of consolidation deformation due to the flow of fiber-resin suspension is measured. The proposed sensor will be a powerful tool for elucidating consolidation mechanisms and for validating composite manufacturing simulations. [ABSTRACT FROM AUTHOR]

A physics-informed neural network (PINN) that combines deep learning with physics is studied to solve the nonlinear Schrödinger equation for learning nonlinear dynamics in fiber optics. A systematic investigation and comprehensive verification on PINN for multiple physical effects in optical fibers is carried out, including dispersion, self-phase modulation, and higher-order nonlinear effects. Moreover, both the special case (soliton propagation) and general case (multipulse propagation) are investigated and realized with PINN. In existing studies, PINN is mainly effective for a single scenario. To overcome this problem, the physical parameters (i.e., pulse peak power and amplitudes of subpulses) are hereby embedded as additional input parameter controllers, which allow PINN to learn the physical constraints of different scenarios and perform good generalizability. Furthermore, PINN exhibits better performance than the data-driven neural network using much less data, and its computational complexity (in terms of number of multiplications) is much lower than that of the split-step Fourier method. The results show that PINN is not only an effective partial differential equation solver, but also a prospective technique to advance the scientific computing and automatic modeling in fiber optics. [ABSTRACT FROM AUTHOR]

In this paper, we will study the propagation properties of nonlinear periodic waves (PW) in a fiber optics for the coupled nonlinear Schrödinger equation with parabolic law with weak non-local nonlinearity (CNLSE-PLWNLNL). We will find the chirped periodic waves (CPW) by using some Jacobi elliptic functions (JEF) and also obtain some solitary waves (SW) like dark, bright, hyperbolic, singular, periodic and other solitons. The resultant chirp associated with each of these optical solitons (OS) will be observed dependent on pulse intensity. The graphical representation of these waves will also be presented. [ABSTRACT FROM AUTHOR]

In this letter, we apply high-bandwidth silicon-based integrated coherent Transmit & Receive Optical Sub-Assembly (IC-TROSA) in long-haul fiber transmission systems. G.654E fiber and Raman amplifiers are employed in the fiber link to reduce the transmission loss and the nonlinear interference. In the experimental demonstration, the silicon-based IC-TROSA can provide similar performance as commercial coherent transceivers. In addition, G.654E fiber can achieve longer transmission distance than G.652D fiber. Moreover, 16 Tb/s ($80\times 200$ Gb/s) Nyquist DP-QPSK and 20 Tb/s ($50\times 400$ Gb/s) Nyquist DP-16QAM transmission over 10000 km and 4000 km fiber distance have been successfully achieved under the threshold of soft-decision forward error correction (SD-FEC) codes with 20% overhead, respectively. [ABSTRACT FROM AUTHOR]

The implementation of distributed strain measurement methods in triaxial and uniaxial tests have demonstrated the development of strain localization, even at early stages. This implies that single point measurement methods are location dependent. The use of distributed methods is required not only to improve the interpreted constitutive parameters obtained from triaxial tests, but also to understand the implications of strain localization in the failure process. This work uses optical fibers in triaxial tests. The developed distributed measurement method was implemented on granite, gabbro, and sandstone samples and tested under different confining pressures, reaching 200 MPa on the granite sample. Using a temporal resolution of 0.25 Hz and 5 mm of spatial resolution, the strain evolution at over 300 locations at the sample surface was measured during testing. When compared to point sensing methods, the use of optical fiber greatly increases the number of measurements at the surface of the sample, and their interpolation provides the entire deformation of the sample surface. In all the tests performed, strain localizations were revealed before failure. A three‐dimensional interpretation of a test, combining an optical scan of the sample and the distributed measurements, show good correlation between the fractures and the strain localization. Plain Language Summary: Triaxial tests are commonly used to describe the response of rock materials under loading and to predict their failure. The sample is assumed to develop a uniform deformation; therefore, single point sensors are used. The recent implementation of computer tomography scans and acoustic emission techniques in triaxial tests have shown the evolution of strain localization prior to failure. This implies that distributed measurement methods are required to improve interpretation of the material behavior and understand its failure mechanisms. This work uses optical fibers in triaxial tests. The developed distributed strain measurement method was compared to widely accepted point measurement methods. It was then used in rock samples, capturing the distributed deformation on their surfaces with higher temporal resolution than the computer tomography scanning method. In all the tests performed, strain localizations were revealed, evolving through the height of the sample. A three‐dimensional reproduction, combining an optical scan and the distributed measurements, show good correlation between the fractures and the strain localization. Key Points: A method developed for distributed strain measurements in high‐confinement triaxial tests using fiber optics sensingThe method has been tested for up to 200 MPa of confining pressure using granite, gabbro, and sandstone samplesThe development of evolving strain localization that corresponds to a fault‐like rupture was observed in all triaxial tests [ABSTRACT FROM AUTHOR]

In this paper, we present an experimental study of the metrological stabilization of a solid-state frequency comb for embedded metrology applications. The comb is a passively mode-locked laser diode based on InGaAs/InP Quantum-dash structure emitting optical lines into a 9 nm bandwidth centered at $1.55~\mu \text{m}$ with a repetition rate of 10.09 GHz. The frequency stabilization is achieved by optical injection locking of the comb with an external cavity laser diode referenced onto a metrological frequency standard. One observes the transfer of the spectral purity from the injection laser to the neighbouring modes of the injected one as well as the transfer of stability to the adjacent modes. The measurement of the long term stability highlights a frequency noise with random walk behavior specific of the passive mode locking process. Demonstration of sidebands of the injection laser at the repetition frequency of the comb also makes it possible to propose a transfer mechanism and to consider a complete stabilization of the frequency comb at a metrological stability level. [ABSTRACT FROM AUTHOR]

Fiber Optic Network is an advanced and modern system technology, which is used in sending pulses of laser light inside a glass of fiber over long distances, widely used in every environment with various sorts of applications in a different field. It is well-known that the main material of fiber optics is glass, therefore it is typical that the temperature can affect the glass during the thermal expansion. This effect will be applied to the properties of the optical components such as refractive index, radius curvature of the fiber optics layers, and also there is an effect on the data transfer through the fiber optics network units. In this paper, the effect of temperature degree on the optical signal and the functions of the fiber optic network will be simulated, measured, and analyzed. The result will be discussed and the conclusion will show the serious points of thermal effects on the optical signal of a fiber-optic network. [ABSTRACT FROM AUTHOR]

According to the Bill-Lambert law, this article reports a flexible optical waveguide sensor based on the polydimethylsiloxane (PDMS) doped with graphite. We quantitatively study the attenuation spectra induced by adding graphite with different particle sizes and amounts into the optical waveguide of the sensor. Adding the graphite’s particle size with $0.5\mu $ m and its concentration of $5\times 10^{-{3}}$ wt% shows that the relationship between the optical attenuation and the tensile strain in the range of 90% is approximately linear. Our further experiment shows that the radial shrinkage of a waveguide is more than 16.8% when the axial tensile strain is larger than 90%, this increases the density of graphite particles on the optical waveguide’s cross-section, resulting in a non-negligible effect on light transmission, which makes the relationship between light attenuation and the tensile strain nonlinear. Our proposed waveguide strain sensor is applied to the motion detection of human joints and muscles. We obtained a series of stable, reliable and durable response no matter the static and dynamic conditions. The sensitivity of the proposed flexible strain sensor is improved by a factor of 3.9 and 1.2 than that of sensors made of the pure PDMS and the polymethylmethacrylate (PMMA), respectively. Meanwhile, it has a high signal-to-noise ratio (SNR) and is insensitive to installation angle errors. There will be a good application prospect in wearable devices that can adapt to the complex curved surface, due to the proposed waveguide strain sensor’s stretchable, sensitive and low-cost characteristics. [ABSTRACT FROM AUTHOR]