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The exploitation of fibre based Raman probes has been challenged by often complicated fabrication procedures and difficulties in reproducibility. Here, we have demonstrated a simple and cost-effective approach for sensing pH through an optical fibre, by employing a wax patterned filter paper-based substrate for surface enhanced Raman spectroscopy (SERS). Through this method, high reproducibility between fibres was achieved. In addition to sensing pH, it was possible to extract fluid samples containing P. aeruginosa for further analysis. This dual purpose fibre is bronchoscope deployable, and is able to gather information about both the host and pathogen, which may lead to an improved treatment plan in future in vivo applications.

This study focuses on the precise in situ online detection of moisture content in paper utilizing a tapered optical fiber evanescent wave sensor made from a polyvinyl alcohol/diatomite moisture-sensitive material and plastic optical fibers. We developed a theoretical model to detect the moisture content in paper based on the principle that a moisture-sensitive material expands upon absorbing water molecules, resulting in changes in its refractive index and altering the sensor's output optical signal. The experiment explored the impact of the fiber core diameter, cone angle, and moisture-sensitive film thickness on the sensor response characteristics. By incorporating a humidity reference unit, the study successfully eliminated interference from changes in ambient humidity on the measurement of the paper moisture content. Theoretical studies revealed that the sensor's output signal is solely dependent on the moisture content of the paper and remains unaffected by fluctuations in ambient humidity. The sensitivity of the sensor is influenced by the thickness of the moisture-sensitive film, fiber core diameter, and cone angle. The sensor can accurately detect the paper's moisture content when the fiber core diameter is 2 mm, cone angle is 15 ± 0.5°, and moisture-sensitive film thickness is 90 μm, achieving a sensitivity of 0.1662 %/%ω and a maximum relative measurement error of less than 3 %. These findings have significant implications for the in situ online measurement of moisture content in solid substrates. • The sensor achieved a sensitivity of 0.1662 %/%ω. • The sensor achieved a maximum relative measurement error of less than 3 %. • Moisture content was determined when the fiber core diameter was 2 mm. • The moisture-sensitive film thickness and taper angle influence sensor sensitivity. • The optimal coating thickness for the PVA/DE moisture-sensitive material was 90 μm. [ABSTRACT FROM AUTHOR]

Digital payments have replaced physical banknotes in many aspects of our daily lives. Similarly to banknotes, they should be easy to use, unique, tamper-resistant and untraceable, but additionally withstand digital attackers and data breaches. Current technology substitutes customers' sensitive data by randomized tokens, and secures the payment's uniqueness with a cryptographic function, called a cryptogram. However, computationally powerful attacks violate the security of these functions. Quantum technology comes with the potential to protect even against infinite computational power. Here, we show how quantum light can secure daily digital payments by generating inherently unforgeable quantum cryptograms. We implement the scheme over an urban optical fiber link, and show its robustness to noise and loss-dependent attacks. Unlike previously proposed protocols, our solution does not depend on long-term quantum storage or trusted agents and authenticated channels. It is practical with near-term technology and may herald an era of quantum-enabled security., (© 2023. The Author(s).)

We studied the optimization of common-path optical coherence tomography (CP OCT) sensitivity through an angled fiber probe. The magnitude of reference power derived from the tip of the fiber was optimized through careful selection of the polishing angle. We experimentally measured the signal-to-noise ratio (SNR) at different polishing angles to validate the effectiveness of this technique. We also obtained OCT images with the reference optimized CP OCT with more than 8 dB improvement in SNR.

Process optimization for increasing the response speed of liquid crystal optical rewritable e-paper was investigated. It is demonstrated that by filling LC in atmosphere condition rewriting time could be decreased to 6 seconds with good repeatability. Increasing the spin coating speed and time could also decrease the azimuthal anchoring energy, but it will cause non-continuous film form of alignment layer which causes large speed dispersion that is not good for practical use. Serial experiments show that with smaller azimuthal anchoring energy the rewriting time could be smaller. The results demonstrate that with proper fabrication process of alignment layer for liquid crystal optical rewritable e-paper, azimuthal anchoring energy could be adjusted to an optimal value which is beneficial for achieving fastest rewriting speed and at the same time strong enough to well align LC. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Orbital angular momentum (OAM) of light is a promising means for exploiting the spatial dimension of light to increase the capacity of optical fiber links. We summarize how OAM enables efficient mode multiplexing for optical communications, with emphasis on the design of OAM fibers. [ABSTRACT FROM AUTHOR]

Optical fibers, serving as sensors and data conduit, are particularly relevant for long-term health monitoring of civil structures. Nevertheless, many challenges associated with the on-site application of such sensors have to be solved, these are mainly related to the application methodology. The objective of this current research is to assess the feasibility and reliability of strain measurements by utilising FBG (Fiber Bragg Grating) optical sensors embedded in two types of FRP (Fiber Reinforced Plastic) packaging. The first device consists of an FRP reinforcing sheet with embedded FBG sensor, conceived for external application on the structural element surface. The FRP packaging of the second device consists of a FRP rebar, conceived for internal or Near Surface Mounted (NSM) applications. These two FRP packages provide the optical fiber with the necessary protection against accidental damage during handling and installation. The mechanical characteristics of the packaging material allow the use of the device for structural reinforcing purpose as well. The paper discusses the various steps in the development of the technology set-up, the physical and the mechanical testing and the in situ validation for the two devices. [ABSTRACT FROM AUTHOR]

With the concept of smart geogrid coming out, many scholars have built optical fiber into the geogrid to form a kind of smart geogrid material with self-sensing function of structural deformation. It can not only reinforce the parts with potential safety hazards, but also have the functions of safety monitoring, intelligent prevention, and control of engineering disasters, which is of great significance for ensuring the safety of tunnel construction and improving the tunnel monitoring methods. Based on predecessors' research on smart geogrid tensile calibration experiment and sensor method simulation and experimental verification, this paper analyzes the smart geogrid and the tunnel surrounding rock as a whole, to study the deformation coordination mechanism between the geogrid material and the tunnel surrounding rock. Referring to the relevant engineering practice case, through finite element numerical simulation, the optimal layout of smart geogrid material was explored, and the principle of discrete curvature reconstruction curve sensing of smart geogrid was optimized by simulating the working conditions of different construction methods and supporting conditions, in order to provide a theoretical basis for the application of smart geogrid material in practical tunnel engineering. [ABSTRACT FROM AUTHOR]

Mode-locked fiber lasers emitting short pulses of light at wavelengths of 2 μm and longer are reviewed. Rare-earth doped silica and fluoride fiber lasers operating in the mode-locked regime in the mid-IR (2–5 μm) have attracted attention due to their usefulness to spectroscopy, nonlinear optics, laser surgery, remote sensing and ranging to name a few. While silica fiber lasers are fundamentally limited to emission wavelengths below 2.2 μm, fluoride fiber lasers can reach to nearly 4 μm. The relative infancy of fluoride fibers as compared to silica fibers means the field has work to do to translate the mode-locking techniques to systems beyond 2 μm. However, with the recent demonstration of a stable, mode-locked 3 μm fiber laser, the possibility of achieving high performance 3 μm class mode-locked fiber lasers looks promising. [ABSTRACT FROM AUTHOR]

With the continuous development of network communication technology, the domestic network has covered the homes of ordinary people, but the indoor coverage system of the network cable network needs to be further improved. The optical fiber distribution system is a signal coverage system integrating GSM, TD-SCDMA, and other standards. It is mainly composed of system access unit, system expansion unit, and system remote unit. Wireless network is an important communication technology, which is easy to use and can be connected wirelessly over long distances. The purpose of this paper is to study an optical fiber distribution system for indoor coverage design of wireless networks, so as to achieve faster and more efficient coverage. In this paper, a wireless network signal processing algorithm is proposed, and a systematic method for designing the wireless network indoor coverage of the optical fiber distribution system is proposed, and the algorithms are compared and tested. The test results in this paper show that the signal strength obtained by the algorithm in this paper is −54.83 dB, while the traditional artificial design algorithm is only −45.97 dB. In addition, the wireless network base point of the algorithm in this paper is also 3 lower than the traditional one. Moreover, the coverage rate achieved by the algorithm in this paper is 3.17% higher than that of the network cable network base point layout given by the genetic algorithm, and the average received signal strength is 3.34 dB higher. In addition, the algorithm in this paper takes 9.1 s, 11.2 s, and 5.3 s for the three scenarios of underground parking lot, large shopping mall, and residential residential area, while the traditional manual design algorithm takes 87.9 s, 108.8 s, and 51.7 s, respectively. The algorithm in this paper is only about 1/10 of the traditional artificial design algorithm. Therefore, it can be concluded that the coverage effect of the wireless network indoor coverage system of the optical fiber distribution system designed in this paper is significantly improved. [ABSTRACT FROM AUTHOR]

In this paper, we skillfully utilize the discriminative ability of the discriminator to construct a conditional generative adversarial network, and propose a scheme that uses few symbols to achieve high accuracy recognition of modulation formats under low signal-to-noise ratio conditions in coherent optical communication. In the one thousand kilometres G.654E optical fiber transmission system, transmission experiments are conducted on the PDM-QPSK/-8PSK/-16QAM/-32QAM/-64QAM modulation format at 8G/16G/32G baud rates, and the signal-to-noise ratio parameters are traversed under experimental conditions. As a key technology in the next-generation elastic optical networks, the modulation format recognition scheme proposed in this paper achieves 100% recognition of the above five modulation formats without distinguishing signal transmission rates. The optical signal-to-noise ratio thresholds required to achieve 100% recognition accuracy are 12.4 dB, 14.3 dB, 15.4 dB, 16.2 dB, and 17.3 dB, respectively. [ABSTRACT FROM AUTHOR]

The temperature dependence of chromatic dispersion is examined for various types of fiber. Its coefficient is found to depend strongly on the dispersion slope. Dispersion-flattened fiber has a significantly low coefficient of -0.0005 (ps/nm/km)/°C, compared with 0.0038(ps/nm/km)/°C for large-core nonzero dispersion-shifted fiber. Transmission lines with low dispersion slopes consisting of pure silica core fiber and dispersion-compensating fiber also exhibit low coefficients of less than -0.001 (ps/nm/km)/°C because of their compensating effects. The different techniques have been proposed to minimize temperature effect on optical fibers such as using multipoint temperature measurement techniques, coupling technique, using different materials which can withstand high degree temperature without fluctuations in performance. [ABSTRACT FROM AUTHOR]

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: The role of the nucleus accumbens (NAc) in chronic neuropathic pain has been suggested, but the role of the NAc in dorsal root ganglion (DRG) neuropathic pain remains unclear. The objective of this study was to determine whether optogenetic stimulation of the NAc influences DRG compression-induced neuropathic pain., Materials and Methods: We established sham or DRG lesions in female Sprague-Dawley rats by L4-5 DRG root compression, and the animals received unilateral injections of optogenetic virus in the NAc core. We employed reflexive pain tests to assess the alterations between the groups at the light on/off states. To determine thalamic firing, we performed single-unit in vivo extracellular recording. For statistical analysis, we used one- or two-way repeated-measures analysis of variance., Results: Compared to sham-operated rats, chronic compressed DRG rats showed elevated behavioral sensitivity and sustained neuronal hyperexcitability in the thalamus. NAc optic stimulation improved pain behaviors and lowered thalamic discharge from ventral posterolateral thalamic nuclei., Conclusions: The NAc core impacts the reward and motivational aspects of chronic neuropathic pain influenced by limbic behaviors to thalamic discharge. Increased thalamic firing activity may result in chronic compressed DRG-induced neuropathic pain, and optogenetic neuromodulation of the NAc can ease chronic pain and thalamic discharge., (© 2019 International Neuromodulation Society.)

Methane gas leakage can lead to pollution problems, such as rising ambient temperature. In this paper, the Vernier effect of a double D-shaped photonic crystal fiber (PCF) in a Sagnac interferometer (SI) is proposed for the accurate detection of mixed methane gas content in the gas. The optical fiber structure of the effective sensing in the sensing SI loop and the effective sensing in the reference SI loop are the same. Both of them adopt the polarization-maintaining photonic crystal fiber (PM-PCF) designed in this paper. The optical fiber structure of the effective sensing in the sensing SI loop deposited with the methane gas-sensitive film is polished to obtain a double-D structure. This operation makes it easier for methane gas to contact the sensitive film and realize the sensor's repeated use. The sensing capability of the methane gas sensor was evaluated utilizing the finite element method (FEM). The numerical simulation results show that when the concentration of methane gas in the environment is 0~3.5%, the average sensitivity of two parallel Sagnac loops is 409.43 nm/%. Using Vernier effect cascade SI loops, the sensitivity of the sensor for detecting methane gas increased by four times. Without considering air and humidity, we provide a practical scheme for the development and design of high-sensitivity methane gas sensors. [ABSTRACT FROM AUTHOR]

In dispersion-managed links with mid-span spectral inversion (MSSI) systems, the symmetry of the cumulative dispersion profile is important for compensating the distorted wavelength division multiplexing (WDM) signals. The triangular dispersion map has antipodal symmetry with respect to the midway optical phase conjugator (OPC). A triangular dispersion map is proposed in this paper that has a singularity in which the lengths of the optical fibers that contribute to forming the cumulative dispersion profile are determined randomly. We analyzed three types for randomly determining and deploying the length of optical fibers to form the triangular dispersion map. We confirmed that triangular dispersion maps combined with MSSI systems are more advantageous for distorted WDM channel compensation than traditional uniform dispersion maps are. In particular, the dispersion map created via the “random-inverse” scheme, which randomly arges the optical fiber lengths of each span before the midway OPC while reversing the arrangement of the optical fiber lengths in the sections after the midway OPC, results in the best compensation. [ABSTRACT FROM AUTHOR]

This paper employs five different general-purpose optimization methods to perform parameter optimization on single-layer hollow antiresonant fibers. It provides guidance on the establishment of hyperparameters for various optimization methods, with the aim of further defining and standardizing the necessary conditions and convergence criteria for applying optimization algorithms to specialty optical fibers. Through numerical experiments, the study ultimately obtains the converged optimal performance and the range of optimized parameter guidance for single-layer, double-layer, and triple-layer antiresonant fibers with different topological structures. [ABSTRACT FROM AUTHOR]

High-speed, low-driving-voltage operation of multiple-quantum-well (MQW) external modulators based on the quantum-confinement Stark effect (QCSE) operating at tong wavelengths are reviewed. We discuss the design and characteristics of ultrafast intensity and phase MQW modulators that have been developed by our group and we compare them with those of other material systems end structures based on a defined figure of merit for external modulator. In addition, we discuss a new integrated tight source that enables external modulation of an in-plane DFB laser to reduce wavelength chirping and coupling loss with a laser and a modulator. Finally, we describe new applications for optical soliton pulse generation using the above intensity modulator. [ABSTRACT FROM AUTHOR]

In this paper, a sixth-order nonlinear partial differential equation which can be used to describe the propagation pulse in optical fibers is studied by using the methods of trial equation and complete discrimination system for polynomial. We have obtained some exact optical wave solutions, including singular solutions, solitary wave solutions, and elliptic function double periodic solutions, which can be completely classified in parameter space. [ABSTRACT FROM AUTHOR]

• Review of characterization techniques for few mode fibers and components. • Focus is on interferometric methods. • Simple interferometric setup for measuring mode coupling and DGD. • Improved algorithm for spatial and spectral resolved imaging for the two modes. • Effect of the rotation of asymmetric modes. This paper reviews characterization techniques for few mode fibers and components. The focus is on interferometric techniques including spatial and spectral resolved imaging (S2). Simple interferometric measurements are shown to be able to give quite comprehensive information including measurement of relative group delay. A new improved algorithm for analyzing S2 data for the case of only two modes is presented. The effect of polarization and rotation of asymmetric modes is treated as well. [ABSTRACT FROM AUTHOR]

We numerically demonstrate the dispersion map configured by random-based residual dispersion per span (RDPS) applied into the mid-span spectral inversion (MSSI) system to mitigate the impact of chromatic dispersion and the fiber nonlinearity in wavelength division multiplexed (WDM) signals. The dispersion map proposed was a scheme in which the RDPS of all optical fiber spans in the front section of the midway optical phase conjugator (OPC) are randomly selected, and the arrangement order of the RDPS in the rear section is inverted from that of the front section. Numerical simulations were performed by evaluating the compensation of the distorted 960 Gb/s WDM signal as a function of the variation of the DCF length and the SMF length, which are involved in determining RDPS. It was confirmed that the compensation effect of the proposed dispersion maps has improved compared to the conventional dispersion map since the dispersion maps examined in this paper have antipodal symmetry around the midway OPC. In particular, it was confirmed that the method of randomly determining the RDPSs by varying the DCF length slightly improved system performance compared to the variation of SMF lengths. We also found that the feature of the RDPS random distribution patterns can achieve excellent compensation for the distorted WDM signal through 50 iterations. [ABSTRACT FROM AUTHOR]

TBM has been widely used in underground engineering and construction, but there is no precedent for the application of open TBM in the inclined shafts of coal mines, which brings new challenges to the support system. The distribution of the axial forces on anchors and the range of loosening of the surrounding rock are crucial considerations in tunnel support design. Existing methods for measuring the axial forces in anchors and determining the extent of loosening in the surrounding rock typically remain at the inspection level, lacking long-term and real-time monitoring capabilities. This paper presents a new self-sensing anchor with embedded optical fibers (made using an improved stirrer) and proposes an intelligent tunnel rock monitoring system. The paper also outlines a method for identifying loosening zones in surrounding rock based on monitoring data and theoretical analysis. Installing self-sensing anchors in the deep sections of the rock surrounding a tunnel provides three-dimensional, round-the-clock real-time monitoring of the axial forces acting on the anchors, using new technology and methods to recognize the deformation characteristics of loosening zones within the surrounding rock. This new self-sensing fiber optic anchor was first applied to an open TBM tunneling project in an inclined shaft in the Kekegai coal mine, and monitoring data indicate that self-sensing optical fiber anchors can accurately reflect stress patterns in real time. The axial force curve can be divided into four segments: the borehole area, the loosening zone, the stable zone, and the anchoring zone. Consequently, it accurately identifies the thickness of loosening zones at different positions within the tunnel's surrounding rock. This information is compared and verified against results obtained from bolt dynamometers and borehole inspection. On this basis, an intelligent monitoring system was established to provide a basis for making engineering construction decisions, which makes tunnel construction smarter and helps technicians timely adjust TBM driving and support parameters. [ABSTRACT FROM AUTHOR]

A reinforced earth wall is a structure in which reinforcement materials are placed in an embankment to build a vertical or nearly vertical wall surface. Such walls have been widely used in roads and in developed land since around 1960. Reinforcement materials have a set service life of 100 years and fall into two types: steel and geosynthetics. To ensure long-term durability, steel reinforcement materials are plated, while geosynthetics are designed with a limit strength designed to resist fracture for 100 years under the conditions of a given load placed on the reinforcement materials. However, owing to the difficulty of assessing the condition of reinforcement materials in soil, this paper proposes solutions based on non-destructive methods. Specifically, it proposes a method of assessing the amount of strain through an embedded optical fiber in the case of geosynthetic reinforcement materials, or magnetic surveying to investigate the degree of corrosion in the case of steel reinforcement materials. This paper demonstrates that it is possible to non-destructively assess the state of either type of reinforcement material. [ABSTRACT FROM AUTHOR]

Radio over fiber (ROF) is a very attractive technology for the increasing demand for flexibility and transmission capacity and due to its high bandwidth and low attenuation, it offers an economic advantage. The wavelength division multiplexing (WDM) is used to multiplex the different wavelengths signals within a single optical fiber. In this paper, WDM-ROF system is analysed with different filters using an optisystem. Results were compared using max Q factor, min BER, and eye height parameters. [ABSTRACT FROM AUTHOR]

Copyright of China Mining Magazine is the property of China Mining Magazine Co., Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lightning strike is one of the main factors affecting power transmission lines and may lead to broken strands and damage of transmission lines, resulting in abnormal power supply. To improve the accuracy of lightning location, this paper presents a polarization optical time-domain reflectometer (POTDR) lightning location method based on orthogonal coding technology. The lightning strike point can be located by detecting the state of polarization (SOP) mutation of Rayleigh backscattering in the POTDR system. The orthogonal coding technology is used to improve the distance and accuracy of POTDR lightning location. Through calculation and simulation analysis, the location accuracy is significantly improved at the same sensing distance compared with the ordinary POTDR lightning location method. The lightning strike location error can be limited to 200 m in 20 km sensing distance which meets the actual engineering needs. The results of this paper are important to improve the operation and maintenance efficiency of transmission lines and reduce maintenance costs in the power industry. [ABSTRACT FROM AUTHOR]

Guided waves (GW) allow fast inspection of a large area and hence have received great interest from the structural health monitoring (SHM) community. Fiber Bragg grating (FBG) sensors offer several advantages but their use has been limited for the GW sensing due to its limited sensitivity. FBG sensors in the edge-filtering configuration have overcome this issue with sensitivity and there is a renewed interest in their use. Unfortunately, the FBG sensors and the equipment needed for interrogation is quite expensive, and hence their number is restricted. In the previous work by the authors, the number and location of the actuators was optimized for developing a SHM system with a single sensor and multiple actuators. But through the use of the phenomenon of acoustic coupling, multiple locations on the structure may be interrogated with a single FBG sensor. As a result, a sensor network with multiple sensing locations and a few actuators is feasible and cost effective. This paper develops a two-step methodology for the optimization of an actuator–sensor network harnessing the acoustic coupling ability of FBG sensors. In the first stage, the actuator–sensor network is optimized based on the application demands (coverage with at least three actuator–sensor pairs) and the cost of the instrumentation. In the second stage, an acoustic coupler network is designed to ensure high-fidelity measurements with minimal interference from other bond locations (overlap of measurements) as well as interference from features in the acoustically coupled circuit (fiber end, coupler, etc.). The non-sorting genetic algorithm (NSGA-II) is implemented for finding the optimal solution for both problems. The analytical implementation of the cost function is validated experimentally. The results show that the optimization does indeed have the potential to improve the quality of SHM while reducing the instrumentation costs significantly. [ABSTRACT FROM AUTHOR]

In the ever-evolving landscape of modern technology, integrating communication and sensing systems has become increasingly essential for a wide range of applications, from military and defense to autonomous vehicles and beyond. The integration offers a convergence of capabilities that enhances operational efficiency and provides adaptability in complex environments. In this paper, we develop, in simulation and experiment, an integrated communication and sensing system, exploring the cutting-edge utilization of spread spectrum and radio-over-fiber (RoF) photonic technologies. RoF technology inherits the benefits of optical fibers, which include low attenuation and longer reach distance compared to other media. First, we consider the integration of communication and sensing functions using a spread spectrum–binary phase-shift keying waveform. In this integrated system, the sensing function is performed using a radar system. The performance of the proposed system is evaluated in terms of the peak-to-sidelobe ratio of the radar correlator output and the bit error rate for the communication system. The results are obtained through extensive MATLAB simulations. Next, we consider the realization of the proposed integrated communication and sensing system using photonics technology. This phase commences with the utilization of specialized photonics-based software for extensive simulations at different fiber lengths, which is an essential foundational step toward the practical implementation of the proposed system using photonics. Lab experiments are also presented to validate the simulation results. [ABSTRACT FROM AUTHOR]

The combination of the dark fiber in existing Optical Fiber Composite Overhead Ground Wire (OPGW) with Distributed Optical Fiber Sensing (DOFS) technology can be used to enable online monitoring and provide early warnings of anomalies in high-voltage transmission lines. Accurate mapping of the optical cable length to the geographic coordinates of actual towers is a key factor in achieving this goal. This paper discusses the principle of using a DOFS system for transmission line tower positioning and presents four available positioning features. To overcome the limitations of single physical parameter positioning, this paper presents a self-developed hybrid DOFS that simultaneously captures Rayleigh backscattering and Brillouin scattering signals. Several physical parameters, including temperature, strain, and vibration, are acquired synchronously. Through hybrid multi-parameter analysis, the rapid and accurate positioning of OPGW line towers is achieved. Experimental results have shown that the proposed method, based on the hybrid DOFS system, can locate up to 82 towers, while the traditional method could only identify 12. The hybrid system was able to complete 80% of the tension towers in 40 h. This paper presents a novel multi-parameter localization method that has the potential to significantly improve the efficiency and reliability of grid operation and maintenance. [ABSTRACT FROM AUTHOR]

A localized surface plasmon resonance (LSPR) sensor based on tapered optical fiber (TOF) using hollow gold nanoparticles (HAuNPs) for measuring the refractive index (RI) is presented. This optical fiber sensor is a good candidate for a label-free RI biosensor. In practical biosensors, bioreceptors are immobilized on nanoparticles (NPs) that only absorb specific biomolecules. The binding of these biomolecules to the receptors changes the local RI around the sensor and this change is detected by the transmittance spectrum of the fiber. Fast, accurate, easy and low-cost disease diagnosis are the advantages of optical fiber biosensors. In this paper, the structure theory is reviewed and the sensor is simulated by the finite difference time domain (FDTD) method and the finite element method (FEM) and the effect of the thickness and diameter of the HAuNPs and the waist diameter of the TOF is investigated. For the structure with HAuNPs thickness (2.5 nm), diameter (50 nm), and the fiber waist diameter of 10 μm, the wavelength sensitivity of 489.8 nm/RIU and full width at half maximum (FWHM) of 50 nm are obtained, which are better than those specifications in some other LSPR fiber sensors. In addition, the sensitivity of the sensor increases about 2-3 times compared to those of sensors with the same structure. Although there are many parameters in human blood that can change its RI, in practical work, the special bioreceptors on the sensor can deactivate other markers except the specific cancer markers, which changes the effective RI. Therefore, this optical fiber sensor is used for label-free detecting the RI of cancer cells and can be used as a biosensor for the detection of early stages of cancers in a non-invasive way, just using human blood samples., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

The integration of fiber optics and plasmonic sensors is promising to improve the practical usability over conventional bulky sensors and systems. To achieve high sensitivity, it typically requires fabrication of well-defined plasmonic nanostructures on optical fibers, which greatly increases the cost and complexity of the sensors. Here, we present a fiber-optic sensor system by using chemical absorption of gold nanoparticles and a replaceable configuration. By functioning gold nanoparticles with aptamers or antibodies, we demonstrate the applications in chemical sensing using two different modes. Measuring shift in resonance wavelength enables the Pb 2+ detection with a high linearity and a limit of detection of 0.097 nM, and measuring absorption peak amplitude enables the detection of E. coli in urinary tract infection with a dynamic range between 10 3 to 10 8  CFU/mL. The high sensitivity, simple fabrication and disposability of this sensing approach could pave the way for point-of-care testing with fiber-optic plasmonic sensors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Quantitative polymerase chain reaction (qPCR) is a well-recognized technique for amplifying and quantifying nuclear acid, and its real-time monitoring capability, ultrahigh sensitivity, and accuracy make it a "golden-standard" tool in both molecular biology research and clinical diagnostics. However, current qPCR tests rely on bulky instrumentation and skilled laboratorians in centralized laboratories, which spatially and temporally separate the sample collection and test, leading to longer sample turnaround times (TATs) and limited working conditions. Herein, we propose an integrated optical fiber real-time polymerase chain reaction (iF-PCR) system that successfully allows convenient sample collection, rapid thermocycling, closed-loop thermal annealing, and real-time fluorescence detection in a tiny capillary reactor. By leveraging the easy-handling capillary-fiber structure and rapid photothermal actuation of the graphene-decorated fiber head, the whole TAT can be shortened, including sampling and 40 thermocycle amplifications, within 23 min, in which an ultrasmall sample volume of ∼15 μL is needed. Furthermore, the thermal amplification and fluorescence detection capability of the optical fiber system was cross-checked by a commercial qPCR instrument. The fiber-optic qPCR strategy can correctly distinguish between positive and negative samples of clinical respiratory syncytial virus (RSV) without the need for laboratory professional skills. Taking advantage of the distance signal transmission nature of optical fibers, the proposed strategy enables remote testing, which can eliminate the necessity of instrument deployment in crowded biosafety laboratories and facilitate potential distributed pathogen testing for coping with a new round of pandemics., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2025 Elsevier B.V. All rights reserved.)

Methods for evaluation of immobilized-small molecule-binding aptamers are rare. In this study, taking the evaluation of 17β-Estradiol (E2) aptamers as an example, we first summarized the reported affinity and specificity results of 16 E2 aptamers, highlighting the issues of insufficient and inconsistent results and the lacking of evaluation of immobilized aptamers. We further exemplified the limited application scope of current affinity techniques by testing the two most widely-applied E2 aptamers, Kim76 and Alsa35, using the three label-free fluorescence assays and two nuclease protection assays. Subsequently, we evaluated the affinity of immobilized-E2 aptamers, Alsa35 and E09, using fiber optic evanescent wave aptasensor (FOEW) based on the competitive binding of target and fluorophore-labeled complementary strand with the fiber surface immobilized-aptamer. The results revealed that Alsa35 had the better affinity and specificity than E09. Using Alsa35-based FOEW, the enzyme-free detection of E2 spiked in river water and human serum was respectively realized with the unprecedented limits of detection (LOD, S/N = 3) of 4.75 (undiluted river water) and 206 pM (undiluted serum). FOEW is a valuable addition to analytical approaches for evaluation of immobilized-aptamers and a general platform for ultrasensitive target detection., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Surface plasmon resonance (SPR) optical fiber sensors are appealing for biomolecular detection due to their inherent characteristics such as flexibility, real-time performance, and high sensitivity. Concurrently, incorporating SPR sensors into wearable devices has emerged as a significant strategy. However, the majority of traditional SPR optical fiber sensors utilize spectrometers for optical readout, which leads to a relatively bulky overall size of the sensing system. Herein, we present the first optical fiber device capable of conducting sensitive SPR measurements and providing direct electronical readout. This has been achieved by integrating a hyperbolic-metamaterial SPR (HMM-SPR) sensor with an on-fiber graphene/PMMA photodetector (oFGPD). The HMM, composed of three pairs of Au/ZrO 2 , has been employed to develop highly sensitive SPR sensors. The oFGPD, which was constructed by transferring a single layer of graphene onto a tapered fiber region and subsequently covering it with a PMMA protecting film, achieved a high responsivity of 3.42 × 10 6  A W -1 (at 14.07 pW) and a rapid response time of approximately 90 ms at 1550 nm. More significantly, we have incorporated an SPR sensor based on a side-polished fiber (SPF) into the oFGPD, enabling an electronical readout technique for environmental refractive index (RI) SPR signals in a broad potential spectral range, from visible to near-infrared, all within a more compact device. This integration has been successfully validated in the detection of urea and glucose concentrations in artificial perspiration. This approach provides a novel direction for SPR sensor detection and establishes a solid foundation for their application in wearable technology., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

This work presents a ZnO-coated no-core optical fiber sensor (OFS) designed for the highly sensitive detection of acetone vapor. Acetone is a key biomarker for diabetes, which is linked to blood glucose levels and can be detected non-invasively through breath analysis. The OFS utilizes a no-core fiber (NCF) as the sensing region, coated with a thin layer of ZnO nanoparticles to enhance evanescent field interaction with the VOCs at the fiber interface. The NCF segment, optimized to 3.4 cm, maximizes coupling efficiency through multi-mode interference (MMI). The OFS was tested with six different VOCs including acetone, methanol, ethanol, isopropanol, toluene and xylene at concentrations ranging from 1 to 10 ppm, as they are commonly exhaled VOCs associated with diabetes. The fabricated OFS demonstrated high sensitivity to acetone (0.116 nm/ppm) and excellent selectivity compared to other VOCs. It exhibited a lower detection limit of 3.26 ppm, rapid response (26 s), and recovery times (32 s) for acetone, with minimal drift (0.2%) over 30 days. Operated at room temperature, this ZnO-coated no-core OFS offers a cost-effective and simple fabrication approach, showing promising potential for non-invasive acetone monitoring in diabetes., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interestsCharusluk Viphavakit reports financial support was provided by Office of the Permanent Secretary, Ministry of Higher Education, Science, Research and Innovation. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Due to the serious biological toxicity and environmental refractory of heavy metal ions, the detection of heavy metal ions in liquids has attracted great attention. A novel fiber optic surface plasmon resonance (SPR) sensor is presented for detecting lead ions (Pb 2 + ) with temperature compensation. The sensitivity of SPR channel to Pb 2+ is up to -41.55 nm/μM and the detection limit is 7.05 nM after three parallel experiments by synthesizing Schiff base and fixing it on the sensor surface. Using femtosecond laser-induced two-photon polymerization (TPP) technology, a compact fiber-tip miniature Fabry-Perot interferometer (FPI) was printed at the end of the fiber-optic SPR sensor, thus realizing the temperature measurement in the process of detecting Pb 2 + . The FPI channel exhibits a linear response to temperature and remains unaffected by Pb 2+ concentration, thus facilitating temperature correction. The experimental results also show that the proposed sensor has the advantages of compact structure, easy to prepare, good stability, specificity and repeatability. Therefore, this kind of sensor has great potential in various biochemical test applications, and opens up a new way to prepare compact and flexible optical sensors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

A novel dual-parameter optical fiber biosensor based on surface plasmon resonance (SPR) for simultaneous measurement of urea and uric acid concentrations is proposed in this paper. Based on the principle of positive and negative electric combination, ZnO nanoparticles is selected as the matrix for immobilizing urease and uricase with selective recognition ability, which can also be used as a sensitizing material to increase the refractive index detection sensitivity of SPR by 22%. Then, Nafion ion exchange membrane was introduced to wrap the urea sensing area to avoid crosstalk caused by the overlap of adjacent sensing areas. The difference in the number of enzymes loaded on ZnO nanoparticles was used to meet the refractive index gap for forming dual SPR detection channels. Experiments indicate that the sensitivity of urea detection is 1.6 nm/mM in the range of 1-9 mM urea concentration. The detection sensitivity of uric acid is 36 nm/mM in the concentration range of 50-500 μM. The detection ability of the sensor to actual biological samples was verified by serum samples, which proved that the sensor has practical application potential and reliable selectivity. It can provide a new idea for the research and development of multi-parameter optical fiber biosensors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Biomarker detection has emerged as an essential complementary approach for early-stage screening of tumors. Conventional methods are constrained by bulky systems, cumbersome operation steps, and low detection accuracy. Here, we demonstrate a dual-resonance optimally configured lossy mode resonance (LMR) immunoprobe for detecting prostate-specific antigen (PSA), a biomarker for prostate cancer (PCa). The dual-resonance structure used in this study introduces low-refractive-index magnesium fluoride (MgF 2 ) as a matching layer before adding indium tin oxide (ITO) as a lossy mode excitation layer to enhance the phase matching between the evanescent wave and the lossy mode to realize dual-resonance. Compared with classical optical fiber LMR, the dual-resonance effect not only improves the detection precision but also features a high accuracy of joint detection. The limit of detection (LOD) of the optical fiber immunoprobe based on dual-resonance for PSA immunoassay can reach down to 52 pg/mL, making it ideally suited for early risk management and prognostic diagnosis of PCa. In addition, the optical fiber immunoprobe is used to detect suspected PCa patients, with a successful recognition rate of 90% compared with that of standard commercially available chemiluminescent assays. This work may pave the way for promising applications of optical fiber immunoprobe for high-precision, high-accuracy, and portable early-stage screening of tumors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

To solve the problems of a few optical fibre line fault samples and the inefficiency of manual communication optical fibre fault diagnosis, this paper proposes a communication optical fibre fault diagnosis model based on variational modal decomposition (VMD), fuzzy entropy (FE) and fuzzy clustering (FC). Firstly, based on the OTDR curve data collected in the field, VMD is used to extract the different modal components (IMF) of the original signal and calculate the fuzzy entropy (FE) values of different components to characterize the subtle differences between them. The fuzzy entropy of each curve is used as the feature vector, which in turn constructs the communication optical fibre feature vector matrix, and the fuzzy clustering algorithm is used to achieve fault diagnosis of faulty optical fibre. The VMD-FE combination can extract subtle differences in features, and the fuzzy clustering algorithm does not require sample training. The experimental results show that the model in this paper has high accuracy and is relevant to the maintenance of communication optical fibre when compared with existing feature extraction models and traditional machine learning models. [ABSTRACT FROM AUTHOR]

The precise evaluation of micro-crack sizes and locations is crucial for the safe operation of structures. Traditional detection techniques, however, suffer from low spatial resolution, making it difficult to accurately locate micrometer-scale cracks. A method and experimental study were proposed in this paper for identifying and locating micro-cracks using optical fiber strain sensing based on OFDR to address this issue. The feasibility of this method for micro-crack detection was verified by the combination of a polyimide-coated sensing optical fiber (PISOF) and tight sheath sensing optical fiber (TSSOF). A calculation method for micro-crack widths based on distributed optical fiber strain curves was established, and the test results of different optical fibers were compared. Through multiple verification experiments, it was found that the strain peak curves of both fiber types could accurately locate micro-cracks with a precision of 1 mm. Additionally, the crack widths could be obtained by processing the distributed strain curves using a computational model, enabling the accurate capture of micro-crack characteristics at the 10 μm level. A strong linear relationship was observed between the optical fiber stretching length and the crack width. Notably, the relative error in calculating the crack width from the strain curve of PI fiber was very small, while a linear relationship existed between the maximum strain value of the TSSOF and the crack width, allowing for the calculation of the crack width based on the maximum strain value. This further validated the feasibility of the method designed in this paper for the analysis of micro-crack characteristic parameters. [ABSTRACT FROM AUTHOR]

In order to achieve a high-precision synchronous detection of two different refractive index (RI) analytes, a D-type surface plasmon resonance (SPR) photonic crystal fiber (PCF) RI sensor based on two channels is designed in this paper. The sensor uses a D-shaped planar region of the PCF and a large circular air hole below the core as the sensing channels. Surface plasmon resonance is induced by applying a coating of gold film on the surface. The full-vector finite-element method (FEM) is used to optimize the structural parameters of the optical fiber, and the sensing characteristics are studied, including wavelength sensitivity, RI resolution, full width at half maximum (FWHM), figure of merit (FOM), and signal-to-noise ratio (SNR). The results show that the channel 1 (Ch 1) can achieve RI detection of 1.36–1.39 in the wavelength range of 1500–2600 nm, and the channel 2 (Ch 2) can achieve RI detection of 1.46–1.57 in the wavelength range of 2100–3000 nm. The two sensing channels can detect independently or simultaneously measure two analytes with different RIs. The maximum wavelength sensitivity of the sensor can reach 30,000 nm/RIU in Channel 1 and 9900 nm/RIU in Channel 2. The RI resolutions of the two channels are 3.54 × 10−6 RIU and 10.88 × 10−6 RIU, respectively. Therefore, the sensor realizes dual-channel high- and low-RI synchronous detection in the ultra-long wavelength band from near-infrared to mid-infrared and achieves an ultra-wide RI detection range and ultra-high wavelength sensitivity. The sensor has a wide application prospect in the fields of chemical detection, biomedical sensing, and water environment monitoring. [ABSTRACT FROM AUTHOR]

As the basic application of fiber optic sensing technology, strain measurement accuracy as a key index needs to be further calibrated and analyzed. In this paper, accuracy calibration experiments and the related analyses of two fiber-optic sensing technologies, the fiber-optic grating (FBG) and optical frequency domain reflectometry (OFDR), are carried out using a standard beam of equal strength and a mature resistive strain gauge (ESG). The fiber-optic single-point strain data for loading and unloading changes of the beams of equal strength show good continuity and linearity, with good cyclic stability, and the error in the strain test data is less than 2% after repeated loading. At the same time, using finite element theory to analyze the data and using the measured data error within 5%, a good strain test curve linearity is achieved and R2 is better than 0.998. After repeated loading and unloading tests, it is verified that the fiber grating and the distributed optical fiber in the strain test have good stability in repeatability accuracy. The calibration experiments and data analysis in this paper further illustrate the three sensing technologies in determining the strain test accuracy and the advantages and disadvantages of the indicators, and the development of the fiber optic sensing technology application provides basic technical support. [ABSTRACT FROM AUTHOR]