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The paper analyses the local well posedness of the initial value problem for the k-generalized Korteweg-de Vries equation for k = 3 with irregular initial data. k-generalized Korteweg-de Vries equations serve as a model of magnetoacoustic waves in plasma physics, of the nonlinear propagation of pulses in optical fibers. The solvability of many dispersive nonlinear equations has been studied in weighted Sobolev spaces in order to manage the decay at infinity of the solutions. We aim to extend these researches to the k-generalized KdV with k = 3. For initial data in classical Sobolev spaces there are many results in the literature for several nonlinear partial differential equations. However, our main interest is to investigate the situation for initial data in Sobolev weighted spaces, which is less understood. The low regularity Sobolev results for initial value problems for this dispersive equation was established in unweighted Sobolev spaces with s ≥ 1/12 and later further improved for s ≥ -1/6. The paper improves these results for 3-KdV equation with initial data from weighted Sobolev spaces. [ABSTRACT FROM AUTHOR]

The paper considers the advantages and disadvantages of existing methods for temperature compensation of data from fiber-optic sensors based on fiber Bragg gratings as part of an embedded system for simultaneous testing of deformation and temperature of polymer composite materials. It is shown that when external temperature testing is impossible, it is most expedient to implement the method of two optical fibers with different sensitivity to at least one of these parameters due to different dopants. Technological issues related to the formation of a spatial topology and the provision of an effective survey of the embedded optical system for monitoring polymer composite materials by the two-fiber method are considered. The results of theoretical research of a linear model of temperature compensation, a model that takes into account the influence of cross sensitivity, as well as a quadratic model of temperature compensation of optical testing data are presented. It has been established that the linear model is the simplest, however, when using it, one should take into account the error associated with the inaccuracy of the approximation of optical inspection data by a linear function. At the same time, it is shown that in order to improve the quality and reliability of the results of optical testing, it is advisable to use a quadratic model of temperature compensation, which provides an error level comparable to the error of the fiber-optic sensor survey device. The results obtained can be used to develop methods for the simultaneous testing of samples, as well as monolithic and three-layer structures from structural layered polymer composite materials with limiting molding conditions (temperature less than 180°C, specific pressure lower than 0.7 MPa), as in the process of bench and other tests, and, in the future, in real operating conditions. [ABSTRACT FROM AUTHOR]

Vibration is a ubiquitous phenomenon that occurs in everyday life and people are exposed to it almost all the time. Most often, vibration is measured using electromechanical devices such as piezoelectric, piezoresistive, or capacitive accelerometers. However, attention should be paid to the limitations of such vibration sensors. They cannot operate in the presence of strong electromagnetic fields. Measurements with electromechanical devices require physical contact between the sensor and the vibrating object, which is not always possible due to the design of the sensor and device. The possibility of a non-contact vibration measurement in harsh environments is provided by the technology of interferometric fibre optic sensors. This paper reports the principle of operation, design aspects, experimentation, and performance of a Mach-Zehnder interferometric setup for the measurement of vibration frequency. There are different sensing arms implemented in the interferometer: single-mode, polarization-maintaining, and tapered optical fibre. The paper emphasises the simplicity of the set-up structure and the detection capabilities based on the interferometric sensing giving the possibility of constructing a commercial vibration sensor for all industry demands. [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]

The paper aims to construct optical solitons and travelling wave solutions to two birefringent nonlinear models which consist of two-component form of vector solitons in optical fibre: the Biswas–Arshed model with Kerr-type nonlinearity and without four-wave mixing terms and the nonlinear Schrödinger equation with quadratic-cubic law of refractive index along with four-wave mixing terms. These nonlinear Schrödinger equations are applied in many physical and engineering fields. Optical solitons are considered in the context of photonic crystal fibres, couplers, polarisation-preserving fibres, metamaterials, birefringent fibres, and so on. Two reliable integration architectures, namely, the extended simplest equation method and the generalised sub-ODE approach, are adopted. As a result, bright soliton, kink and dark soliton, singular soliton, hyperbolic wave, a periodic wave, elliptic function solutions of Weierstrass and Jacobian types, and other travelling wave solutions, such as breather solutions and optical rogons, are derived, together with the existence conditions. In addition, the amplitude and intensity diagrams are portrayed by taking appropriate values for a few selected solutions. Furthermore, based on linear stability analysis, the modulation instability was explored for the obtained steady-state solutions. The reported results of this paper can enrich the dynamical behaviours of the two considered nonlinear models and can be useful in many scientific fields, such as mathematical physics, mathematical biology, telecommunications, engineering and optical fibres. This study confirms that the proposed approaches are sufficiently effective in extracting a variety of analytical solutions to other nonlinear models in both engineering and science. [ABSTRACT FROM AUTHOR]

Aerosol particles experience hygroscopic growth at enhanced relative humidity (RH) which leads to changes in their optical properties. We developed the white-light humidified optical particle spectrometer (WHOPS), a new instrument to investigate the particles' hygroscopic growth. Here we present a detailed technical description and characterization of the WHOPS in laboratory and field experiments. The WHOPS consists of a differential mobility analyzer, a humidifier/bypass and a WELAS (white-light aerosol spectrometer) connected in series to provide fast measurements of particle hygroscopicity at sub-saturated RH and optical properties on airborne platforms. The WELAS employs a white-light source to minimize ambiguities in the optical particle sizing. In contrast to other hygroscopicity instruments, the WHOPS retrieves information of relatively large particles (i.e. diameter D > 280 nm), therefore investigating the more optically relevant size ranges. The effective index of refraction of the dry particles is retrieved from the optical di15 ameter measured for size-selected aerosol samples with a well-defined dry mobility diameter. The data analysis approach for the optical sizing and retrieval of the index of refraction was extensively tested in laboratory experiments with polystyrene latex size standards and ammonium sulfate particles of different diameters. The hygroscopic growth factor (GF) distribution and aerosol mixing state is inferred from the optical size distribution measured for the size-selected and humidified aerosol sample. Laboratory experiments with pure ammonium sulfate particles revealed good agreement with Köhler theory (mean bias of ~ 3% and maximal deviation of 9% for GFs at RH= 95 %). First airborne measurements in the Netherlands observed GFs (mean value of the GF distribution) at RH=95% between 1.74 and 2.67 with a median of 1.94 for particles with a dry diameter of 500 nm. This corresponds to hygroscopicity parameters (k) between 0.21 and 0.93 with a median of 0.33. The GF distributions indicate externally mixed particles covering the whole range of GFs between ~ 1.0-3.0. On average ~ 74% of the particles were "more hygroscopic" with GFs> 1.5, ~ 15% were non- or slightly hygroscopic with GF< 1.1 and the remaining ~ 11% were "less hygroscopic" with 1.1 < GF < 1.5. The more hygroscopic mode sometimes peaked at GF> 2, indicating influence of sea salt particles, consistent with previous ground-based particle hygroscopicity measurements in this area. The mean dry effective index of refraction for 500nm 5 particles was found to be rather constant with a value of 1.42±0.04. [ABSTRACT FROM AUTHOR]

This paper proposed a strategy of tracking pipe PIG utilizing Fiber Optic Distributed Vibration Sensor (FODVS) and YOLO object detection algorithm. Phase sensitive Optical Time Domain Reflectometer (ϕ-OTDR) is employed as the distributed sensor to collect the real field vibration signal generated as a result of the collision between leather bowl and weld joint. The space-time graphs of ϕ-OTDR are prepared to construct data sets to train a typical YOLOv3 net model. The trained model is proved to be able to accurately capture the invert-V signature in the space-time graph thus revealing the real time position of a PIG. This paper provides a concept-proof preliminary demonstration on the promising combination of FODVS and object detection scheme for pursuing better performance of events recogntion. [ABSTRACT FROM AUTHOR]

Data explosion and higher service level agreements (SLA) are common terminologies in modern communication networks. Recent advancements toward 5G networks add to the complexity where billions of devices, both static and mobile, are connected generating trillions of megabits of data flooding the network and where service providers scuffle daily to deliver key performance indicators: Lower latency, longer battery life, higher data rates, ultra-high reliability, and more connected devices. The optical-fiber world simultaneously witnesses a denser, fiber-rich network infrastructure which is critically challenged in fast economically developing countries by heavy construction of roads and other infrastructures that inflict repeated and unpredictable cuts to the extent that traffic is simultaneously interrupted in up to 10% of the optical links. Thus, network resiliency to fiber failures is already and will continue to be a top priority for operators. Depending on the SLA, operators choose from various resiliency options, e.g., at single network layers or across multiple ones, with dedicated protection or shared restoration, depending on decisive factors like network availability and total cost of ownership (TCO). With traditional network architectures, high resiliency comes with significantly increased TCO involving optical transport network (OTN) switches, L1 protection switching, and L1 restoration. This translates into high CAPEX and excessive space and power consumption, hampering the desirable seamless scalability with the continuously increasing demand for more capacity. This paper explores an alternative hyperscale network architecture, which is adaptable and resilient to multiple fiber failures, thus delivering committed service levels to the end users and which, at the same time, significantly reduces network cost compared to a traditional all OTN-switched network. The hyperscale architecture exploits low footprint carrier grade, data center interconnect type high-density transponders and cost-effective optical protection switching and restoration via software defined networking control. The paper also describes a routing and grooming algorithm to dimension a shared resource pool for optical restoration and a statistical simulation method for time effective execution, simulating failures over a carefully selected sub-set of failure scenarios to guarantee a high degree of network availability. Via network simulation, the paper demonstrates that multiple failure resiliency and cost effectiveness do not necessarily represent a contradiction in transport networks as long as an appropriate network architecture is chosen and that efficient network planning and optimization are applied. [ABSTRACT FROM AUTHOR]

Detecting partial discharge (PD) in gas-insulated switchgear (GIS) is an effective way to diagnose the insulation state of GIS. When PD occurs in GIS, optical and electromagnetic signals will be emitted from the discharge source. PD can be detected by analyzing these signals. At present, the ultrahigh-frequency (UHF) method is one of the most popular methods for detecting the PD in GIS. However, the optical method has not been in the field due to the problem of mounting optical sensor into GIS, even though it has higher sensitivity and better anti-interference performance. To settle this problem, a novel GIS PD detection sensor integrated with the optical fiber and UHF method is developed in this paper, which can fully utilize the advantages both of UHF and optical methods. The simulation results indicate that the integrated sensor can be mounted into GIS on the premise of not affecting the electric field distribution in GIS. In addition, the integrated sensor has a good UHF performance. The PD signals of typical defects at several locations were measured in a physical GIS using the integrated sensor. The results show that the integrated sensor can detect the optical and UHF signals induced by PD at the same time. The optical method has higher sensitivity than the UHF method for the protrusion defect. The amplitude and the number of the optical signals induced by PD clearly decrease with the increase in the detection distance. The studies in this paper are helpful to improve the accuracy and sensitivity of PD detection in GIS on site. [ABSTRACT FROM AUTHOR]

In this paper, we describe the implementation and test of a biaxial optical accelerometer based on fiber Bragg gratings using ultra-high numerical aperture (UHNA) optical fiber. The characteristics of the UHNA optical fiber, such as the decrease of the fiber Bragg gratings reflectivity after the sensor mounting, were compared with the GF1 photosensitive one. The proposed sensor enables to measure acceleration in two orthogonal directions, making it suitable for vibration analysis in electrical machines and structural health monitoring. The initial project was based on finite-element analysis, experimental test, and analytical response, where it was possible to predict the resonant frequency of the mechanical system of approximately 650.00 Hz. After mounting with the optical fiber, the system was characterized allowing the determination of the resonant frequencies in both sensitive directions; the values of 1232.50 Hz and 1272.50 Hz were estimated for the $x$ -axis and the $y$ -axis. This paper enabled to validate the application of the UHNA optical fiber in the development of small sensors and high radius of curvatures, thus providing the motivation for future applications. [ABSTRACT FROM AUTHOR]

In this paper, the changes of oxidation temperature of sulfide corrosion and the deficiency of distributed optical fiber application were analyzed. The test platform of oxidation temperature of sulfide corrosion was established, and the performance test of optical fiber and the simulation of oxidation temperature of sulfide corrosion were realized. The hardware part of the control system used STM32 as the controller, the software part was based on the process characteristics of the controlled object, using MATLAB to carry out the simulation of PID, fuzzy, fuzzy PD plus I, fuzzy PID algorithms, and their performance are evaluated using both single indexes and comprehensive indexes. The experimental results also showed that the proposed fuzzy PID can achieve better control performance with less overshoot and shorter setting time. Therefore, the fuzzy PID was chosen as the temperature control algorithm to build the optical fiber sensor test platform, and an alarm method for testing the oxidation temperature of large area sulfide corrosion based on the optical fiber performance was obtained. Then, considering the influence of spatial resolution on optical fiber sensor, this paper used piecewise PID to simulate the temperature rise process of three stages of sulfurization corrosion and oxidation. The results showed that the alarm method of oxidation temperature of sulfurization corrosion has limitations for small-scale oxidation of sulfurization corrosion, and it needed to be combined with machine learning to identify temperature anomaly. [ABSTRACT FROM AUTHOR]

This paper aims to review Fiber Bragg Grating sensor technology and state of the art, focusing for the application of the technology for temperature measurement in electric motors, to evaluate the thermal phenomena in electric motors for industrial porpoises. [ABSTRACT FROM AUTHOR]

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Because of the problem of low recognition accuracy in the recognition of intrusion vibration events by the distributed Sagnac type optical fiber sensing system, this paper combines the traditional optical fiber vibration signal recognition idea and the characteristics of automatic feature extraction by a convolutional neural network (CNN) to construct a new endpoint detection algorithm and a method of fusing multiple–scale features CNN to recognize fiber vibration signals. Firstly, a new endpoint detection algorithm combining spectral centroid and energy spectral entropy product is used to detect the vibration part of the original signal, which is used to improve the detection effect of endpoint detection. Then, CNNs of different scales are used to extract the multi–level and multi–scale features of the signal. Aiming at the problem of information loss in the pooling process, a new method of combining differential pooling features is used. Finally, a multi–layer perceptron (MLP) is used to recognize the extracted features. Experiments show that the method has an average recognition accuracy rate of 98.75% for the four types of vibration signals. Compared with traditional EMD and VMD pattern recognition and 1D–CNN methods, the accuracy of the optical fiber vibration signal recognition is higher. [ABSTRACT FROM AUTHOR]

With the emergence of new services, the complex optical network environment makes it more difficult to predict network anomalies. This paper proposes a multi-index anomaly prediction scheme with hybrid supervised/unsupervised deep learning for elastic optical networks. Aimed at complex optical network indicators, the scheme presents three phases to enhance the abnormal prediction. The scheme first selects the most influential indicators of anomaly label among the mass of network indicators by calculating the Spearman correlation coefficient. Then, considering the timeliness of network data, it predicts time series of different indicators to analyze future network conditions by using long short-term memory neural network. In order to improve the accuracy and efficiency of the anomaly detection model, the scheme further establishes a deep neural network for anomaly classification. We also discuss how to process data without anomaly labels. The feasibility of the proposed scheme is verified on a real network dataset. Experimental results show that the scheme can predict the occurrence of future network anomalies with high accuracy, protect network services from potential abnormalities, and enhance the stability and robustness of the network. [ABSTRACT FROM AUTHOR]

This paper presents a high-precision transfer system of time and RF frequency via the fiber optic link based on secure encryption. On the basis of the two-way time transfer of optical fiber, a security strategy composed of an SM2 encryption algorithm is introduced, which can resist the security risk of time information being tampered with. The experimental results show that the developed picosecond-precision fiber-optic time transfer equipment can ensure high stability while realizing the encryption function. Time synchronization stability in terms of time deviation (TDEV) of 1 PPS can reach around 10.7 ps at 1 s and 7.1 ps at 10 s averaging time. The stability of the 10 MHz frequency can reach around 4.7 × 10−12 at 1 s and 1.1 × 10−12 at 10 s averaging time. There is no significant difference in time transfer accuracy, compared with unencrypted conditions. Furthermore, this paper realizes a ring time transfer network via a 150 km fiber-optic link with three nodes using three devices. The TDEV of 1PPS can reach around 20.8 ps at 1s averaging time. This paper provides a reference to establish a high-precision, safe, and stable time synchronization fiber network in the future. [ABSTRACT FROM AUTHOR]

Sensing of data or object is a mature research domain where intelligent devices, may possibly be embedded with the artificial intelligence-based techniques, are placed in the closed vicinity of the object or phenomenon. This sensing activity becomes more complex if it is related to the measurements of an object which is required to be accurate and precise. In this paper, the reflection interference spectrum method is used to measure the flatness of the surface of the object. The thickness of the tested object is between 0.4 and 16 μm. The optical fiber sensor is moved on the surface of the object, and the reflection spectrum of each point on the surface of the object is analyzed. The thickness of each point, and through the movement of the stepping motor, the thickness of different points on the object is continuously measured, so as to obtain the surface topography of the object. This method has no destructive effect on the surface of the object, has no lateral test range limitation, and has a simple test system structure, High test accuracy, and reliable test results. [ABSTRACT FROM AUTHOR]

The optical parametric amplifier (OPA) has attractive features for optical communications, such as a wideband, high gain, and fast transient response. In addition, by using idler light, which is phase-conjugated light generated in the amplification process, various kinds of optical signal processing, such as fiber-nonlinearity mitigation, wavelength conversion, and phase-sensitive amplification, can be performed. A periodically poled LiNbO3 (PPLN) waveguide is an χ(2)-based optical parametric amplification medium, and it makes both wideband and high-gain amplification possible. We developed a 4-port PPLN module that can combine signal light and pump light into a PPLN waveguide with low loss. In this paper, we overview the applications of OPA to WDM optical fiber transmission and explain the configurations of an OPA using 4-port PPLN modules. As applications of our PPLN-based OPA, we introduce the demonstration of wideband inline amplification exceeding 5 THz. Furthermore, we demonstrate inter-band wavelength conversion between C- and S-bands using PPLN waveguides developed for multi-band optical transmission applications. [ABSTRACT FROM AUTHOR]

The ever increasing capacity demand on optical networks and the slowdown of improving spectral efficiency lead to the solution of utilizing more wavelength band in existing optical fibers. More and more operators will extend from C band to C+L bands, or plan to deploy C+L systems, and in future they may utilize more of other bands. This paper firstly discusses different optical layer architectures for multi-band system. Using optical components that can natively support multi-band is attractive to us, because in this way the multi-band system can be planned and operated similarly with the single-band system, which is customer friendly and potentially more economical. We address mainly three technical challenges in this paper. The first one is the wide-band fiber optical amplifier (OA). After a short review of recent research progress, we propose a hybrid erbium-doped fiber (EDF) and bismuth-doped fiber (BDF) based OA approach, and demonstrated single-stage amplification over 100 nm in extended C+L bands. The second challenge is the optical cross connect based on wavelength selective switch (WSS). It is not trivial to realize a C+L-band WSS while preventing the key optical parameters (filtering bandwidth, loss, channel isolation, etc.) to be degraded. We analyze different technical schemes, and propose an optical design based on an LCoS with a large panel size and a high-dispersion diffraction grating. The optical design and simulation on a 2×35 WSS reveals this approach can support 100-nm extended C+L spectrum and is promising for commercialization. The third challenge is the SRS induced WDM channel power inequality, which is more severe for multi-band system. We propose a solution by using OAs with a novel optical spectrum processor (OSP). Simulation and experiment showed that the power of the WDM channels can be equalized on a per span basis, which can prevent accumulation of stimulated Raman scattering (SRS) induced wavelength division multiplexing (WDM) channel power transfer and can meanwhile keep the optical signal to noise ratio (OSNR) of WDM channels well equalized. [ABSTRACT FROM AUTHOR]

This paper reviews the most recent advances on next-generation fibers for space-division-multiplexed transmissions. These fibers can be classified into different categories, depending on the way the inherent crosstalk issue is addressed, and have thus different characteristics and limitations. Comparisons of their performances and insights in their different potentials are also provided. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a novel shape-sensing method based on deep learning with a multi-core optical fiber for the accurate shape-sensing of catheters and guidewires. Firstly, we designed a catheter with embedded multi-core fiber containing three sensing outer cores and one temperature compensation middle core. Then, we analyzed the relationship between the central wavelength shift, the curvature of the multi-core Fiber Bragg Grating (FBG), and temperature compensation methods to establish a Particle Swarm Optimization (PSO) BP neural network-based catheter shape sensing method. Finally, experiments were conducted in both constant and variable temperature environments to validate the method. The average and maximum distance errors of the PSO-BP neural network were 0.57 and 1.33 mm, respectively, under constant temperature conditions, and 0.36 and 0.96 mm, respectively, under variable temperature conditions. This well-sensed catheter shape demonstrates the effectiveness of the shape-sensing method proposed in this paper and its potential applications in real surgical catheters and guidewire. [ABSTRACT FROM AUTHOR]

In industry and architecture, real-time and complete measurement of structures has become a research frontier since it is directly related to the safety of life and property. Optical fibers have the potential to monitor constructions due to advantages such as small size, anti-electromagnetic interference, etc. However, existing research on optical fiber sensors pays attention to the sensing fiber itself and ignores the layout of the optical fibers. As a result, currently available fiber sensors are only suitable for monitoring one-dimensional rigid structures such as surgical robots and puncture needles. They may face challenges when measuring the freeform surfaces encountered in industrial and architectural scenarios. In this paper, a cross-orthogonal measurement method based on optical fiber shape sensors is proposed to meet the shape measurement requirements of freeform surfaces. The cross-orthogonal network allows global measurement and performs surface reconstructions more easily as compared to single-fiber arrays. It also divides the sensing fiber into several segments that are reconstructed separately (with different initial frames), avoiding the cumulative error at the end of the sensing fiber. Results of verification experiments using four-core fibers indicate that the presented method can improve measurement accuracy. [ABSTRACT FROM AUTHOR]

Fiber sensors possess characteristics such as compact structure, simplicity, electromagnetic interference resistance, and reusability, making them widely applicable in various practical engineering applications. Traditional fiber sensors based on different microstructures solely rely on the thermal expansion effect of silica material itself, limiting their usage primarily to temperature or pressure sensing. By employing thin film technology to form Fabry–Perot (FP) cavities on the end-face or inside the fiber, sensitivity to different physical quantities can be achieved using different materials, and this greatly expands the application range of fiber sensing. This paper provides a systematic introduction to the principle of FP cavity fiber optic sensors based on thin film technology and reviews the applications and development trends of this sensor in various measurement fields. Currently, there is a growing need for precise measurements in both scientific research and industrial production. This has led to an increase in the variety of structures and sensing materials used in fiber sensors. The thin film discussed in this paper, suitable for various types of sensing, not only applies to fiber optic FP cavity sensors but also contributes to the research and advancement of other types of fiber sensors. [ABSTRACT FROM AUTHOR]

We demonstrate the application of fluorescence optical fiber coupled to a telecom grade fiber as a sensor for alpha particles using alpha-specific ZnS(Ag) scintillation materials whose wavelength is down-shifted into a low-loss region of the telecom grade fiber transmission band. Telecom-grade fiber optics offer a solution for sensing alpha radiation in deep repositories and cask storage for radioactive materials due to the stability of SiO2 under normal environmental conditions and its relative radiation hardness at low radiation doses. Long-term nuclear waste storage facilities require sensors for the detection of leakage of radioactive materials that are maintenance-free, do not require power and can survive with no 'wear out' mechanisms for decades. By accomplishing the wavelength transformation, we maximize efficiencies in the detection of α-particles and signal transport and can detect alpha scintillation at distances on the order of >1 km with a sensor that is ~3% efficient and can be easily scaled as a sensor array. This paper describes the construction and testing of the sensor including manufacture of the controlled thickness films, verification of the wavelength shift from 450 to 620 nm and optimization of the sensitivity as a function of thickness. We also model the relative sensitivity of the film as a function of film thickness, and we demonstrate a signal-to-noise ratio of 10 at a range of greater than 1 km., (Published by Oxford University Press on behalf of The Japanese Radiation Research Society and Japanese Society for Radiation Oncology 2023.)

For specific recognition and sensitive detection of triglycerides (TGs), an optical fiber sensor (OFS) based on an enhanced core diameter mismatch was proposed. The sensitivity of the sensor is significantly increased due to the repetitive excitation of the higher-order cladding modes. A technique for immobilizing lipase using covalent binding technology was presented and demonstrated by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy. The interference dip of the sensor was shifted due to TGs being hydrolyzed in the presence of lipase. The sensor shows an optimal response within 3 min and exhibits a high sensitivity of 0.9933 nm/(mg/ml) and a limit of detection of 0.0822 mg/ml in the concentration range 0-8 mg/ml at a temperature of 37 °C and a pH of 7.4. The response of the sensor to TGs concentration at different temperatures and pH was investigated. The reproducibility, reusability, and stability of the proposed sensor were tested and verified experimentally. The biosensor is highly specific for TGs and unaffected by many other interfering substances. Further, the measurement of TGs concentration at different temperatures was realized. This method provides a new way to detect TGs rapidly and reliably and has potential applications in medical research and clinical diagnosis., 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 © 2023 Elsevier B.V. All rights reserved.)

This paper reports a sensor architecture for continuous monitoring of biomarkers directly in the blood, especially for ICU/CCU patients requiring critical care and rapid biomarker measurement. The sensor is based on a simple optical fiber that can be inserted through a catheter into the bloodstream, wherein gold nanoparticles are attached at its far distal end as a plasmonic material for highly sensitive opto-chemical sensing of target biomolecules (glucose in our application) via the excitation of surface plasmon polaritons. For specificity, the nanoparticles are functionalized with a specific receptor enzyme that enables the localized surface plasmon resonance (LSPR)-based targeted bio-sensing. Further, a micro dialysis probe is introduced in the proposed architecture, which facilitates continuous monitoring for an extended period without fouling the sensor surface with cells and blood debris present in whole blood, leading to prolonged enhanced sensitivity and limit of detection, relative to existing state-of-the-art continuous monitoring devices that can conduct direct measurements in blood. To establish this proof-of-concept, we tested the sensor device to monitor glucose in-vivo involving an animal model, where continuous monitoring was done directly in the circulation of living rats. The sensor's sensitivity to glucose was found to be 0.0354 a.u./mg.dl-1 with a detection limit of 50.89 mg/dl.

This paper presents a novelty approach to usage of the fiber-optic phase-based sensor in railway transportation. We designed and tested the real deployment of this sensor working on the principle of light interferences within optical fibers. The proposed construction of the sensor allowed to increase the sensitivity and thanks to this can be detected and calculated individual axles and wheels of tram vehicles. We performed long-time period measurements (April to September 2019) in diverse climatic conditions, including measurements of 642 tram passages (several different construction types) in real urban traffic. The detection accuracy level was slightly above 99.4%. [ABSTRACT FROM AUTHOR]

The paper makes a survey of the optical fiber network installed at Deenbandhu Chhotu Ram University of Science and Technology (DCRUST) using reliability analysis, cost-benefit analysis and performance evaluation. Various reliability modeling-related aspects to calculate the reliability of the system have been analyzed. The proposed Markov model includes two units: one is operative unit and the other is hotstandby unit. Hotstandby unit is an optical fiber-based ring which acts as a protection ring. Operative unit is Optical Fiber Cable (OFC) of DCRUST. If working path (operative unit) fails, communication is done through protection path (hotstandby); if both units fail, then the whole system fails. Inspection, repair and replacement are done by regular repairman. The paper also includes a study of various measures of system effectiveness, different reliability parameters to evaluate profit and other measures related to the system. Graphical analysis between various system parameters has also been made. [ABSTRACT FROM AUTHOR]

This paper describes the characteristics of graded-index (GI) core Y-branched polymer optical waveguides as optical couplers for multimode fibers (MMFs) in coarse wavelength division multiplexing links with a restricted mode launch function. In this paper, we compare two GI-core Y-branched waveguides fabricated using different methods: the Mosquito method and the imprint method. Error free transmission is confirmed when transmitting a 25.6125-Gbps NRZ optical signal (PRBS31) at 850-nm wavelength through a 100-m long OM3 fiber using the waveguide as an optical coupler. We also discuss the function of a restricted mode launch exciter for a 1-km long MMF. From the effective modal bandwidth analysis, realizing higher bandwidth-distance product in long MMFs should be possible by reducing the core size of the waveguide coupler. [ABSTRACT FROM AUTHOR]

This special issue includes extensions of invited and top-scored optical networking papers that were presented at the Optical Fiber Communication (OFC) Conference, held in San Diego, CA, March 11-15, 2018. We present an overview of the array of topics covered in the papers, tied in with some historical perspectives on OFC. [ABSTRACT FROM AUTHOR]

In this paper, we propose a novel type of hollow-core anti-resonance fiber (HC-ARF). The cladding region of this fiber is formed by a combination of nested tubes and U-shaped tubes, and the centrally symmetric arrangement significantly reduces sensitivity to polarization. The influence of parameters on the performance of the designed HC-ARF LMA is analyzed by a finite element algorithm. The simulation results demonstrate that the designed structure achieves a large mode area of 3180 µm2, bending loss of 2 × 10−2 dB/km, and confinement loss of 5 × 10−3 dB/km at a wavelength of 1064 nm. Similarly, at a wavelength of 1550 nm, the large mode area, bending loss, and confinement loss are 3180 µm2, 1.4 × 10−2 dB/km, and 4 × 10−2 dB/km, respectively. These results indicate unprecedentedly large mode areas and ultra-low losses compared to previous studies. Within the bending radius under consideration, the bending loss remains below 1.35 × 10−2 dB/km. Furthermore, by increasing the fiber radius, the large mode area can reach an extraordinary 6250 µm2. The proposed device exhibits excellent mode area and outstanding polarization insensitivity, along with favorable bending performance. We believe that the designed fiber holds promising applications in high-power miniaturized fiber lasers, fiber amplifiers, and various high-power fiber communication systems, and it can be applied in sensors that require polarization insensitivity and better bending performance. [ABSTRACT FROM AUTHOR]

In recent years, optical fibers have found extensive use in special environments, including high-energy radiation scenarios like nuclear explosion diagnostics and reactor monitoring. However, radiation exposure, such as X-rays, gamma rays, and neutrons, can compromise fiber safety and reliability. Consequently, researchers worldwide are focusing on radiation-resistant fiber optic technology. This paper examines optical fiber radiation damage mechanisms, encompassing ionization damage, displacement damage, and defect centers. It also surveys the current research on radiation-resistant fiber optic design, including doping and manufacturing process improvements. Ultimately, it summarizes the effectiveness of various approaches and forecasts the future of radiation-resistant optical fibers. [ABSTRACT FROM AUTHOR]

Detecting hydrogen leaks remains a pivotal challenge demanding robust solutions. Among diverse detection techniques, the fiber-optic method distinguishes itself through unique benefits, such as its distributed measurement properties. The adoption of hydrogen-sensitive materials coated on fibers has gained significant traction in research circles, credited to its operational simplicity and exceptional adaptability across varied conditions. This manuscript offers an exhaustive investigation into hydrogen-sensitive materials and their incorporation into fiber-optic hydrogen sensors. The research profoundly analyzes the sensor architectures, performance indicators, and the spectrum of sensing materials. A detailed understanding of these sensors' potentials and constraints emerges through rigorous examination, juxtaposition, and holistic discourse. Furthermore, this analysis judiciously assesses the inherent challenges tied to these systems, simultaneously highlighting potential pathways for future innovation. By spotlighting the hurdles and opportunities, this paper furnishes a view on hydrogen sensing technology, particularly related to optical fiber-based applications. [ABSTRACT FROM AUTHOR]

The humidity has often been measured through a single point sensor. Where, the humidity could be varied at different locations as well as depending on environmental conditions. The present paper developed the dual point humidity measuring sensor by using a polymer optical fiber (POF) based on a single illuminating fiber. The sensor's basic structure is to twist two fibers and bend them at a certain radius. However, the dual point sensor is developed through the cascading of twisted micro bend (TMB-1 and TMB-2). The twisting of fibers couples the light from one fiber to another fiber through the side coupling method. An increase in the humidity level leads to a change in the reflective index, which helps to get variation in coupled light intensity. To measure the humidity, the dual point sensors are placed into the control humidity chamber at two random positions. The power reading variation is significantly linear when the humidity level increases from 30 to 80%. The sensor has a fast response of about 1 s and a recovery time of about 4 s. Furthermore, the chemical coating is applied to improve the sensor's sensitivity. Between 30 and 80% range of humidity, the both sensors of dual point TMB-1 and TMB-2 have appropriate sensitivity and detection limits, which is about 680.8 nW/% and 763.9 nW/% and 1.37% and 1.98%, respectively. To measure the humidity at variable positions, the present dual points humidity sensor is well-stable, easy, and straightforward, which uses a less expensive method. [ABSTRACT FROM AUTHOR]

A fiber-based Fabry–Perot (FP) optical sensor is well-suited for the rapid and selective detection of gas molecules, including volatile organic compounds (VOC), explosive analytes, etc. The sensing probe of a fiber-based Fabry–Perot (FP) sensor is achieved through the deposition of a thin vapor-sensitive material on a cleaved fiber end-face, primarily using the dip-coating method. Because the sensitivity of the FP sensor is closely tied to its cavity length, it is crucial for the coating mechanism to consistently create FP cavities of the same length and thickness. The paper details a process for the controlled deposition of polymer onto an optical fiber, achieved through dip coating. The determination of the shape, size, and other properties of the polymer-based FP cavity involved a comprehensive analysis of the coating steps. Fabricated sensors were further used to evaluate the temporal progression of acetone sensing experiments in response to VOC. Taken as a whole, the outcomes outlined in this paper underscore the potential for achieving consistent coating/cavity thickness in a single-mode fiber. [ABSTRACT FROM AUTHOR]

In this paper, an improved complex-valued convolutional neural network (CvCNN) structure to be placed at the received side is proposed for nonlinearity compensation in a coherent optical system. This complex-valued global convolutional kernel-assisted convolutional neural network equalizer (CvGNN) has been verified in terms of Q-factor performance and complexity compared to seven other related nonlinear equalizers based on both the 64 QAM experimental platform and the QPSK numerical platform. The global convolution operation of the proposed CvGNN is more suitable for the calculation process of perturbation coefficients, and the global receptive field can also be more effective at extracting effective information from perturbation feature maps. The introduction of CvCNN can directly focus on the complex-valued perturbation feature maps themselves without separately processing the real and imaginary parts, which is more in line with the waveform-dependent physical characteristics of optical signals. Based on the experimental platform, compared with the real-valued neural network with small convolutional kernel (RvCNNC), the proposed CvGNNC improves the Q-factor by ∼2.95 dB at the optimal transmission power, while reducing the time complexity by ∼44.7%. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) bonding technology is widely used across industries. As the curing reaction is initiated via an external light source, the use of fast-curing structural UV acrylates has so far been limited to joint designs with at least one transparent joining part. By introducing a side-emitting polymer optical fiber textile into the adhesive layer, which acts as an embedded light source, the technology can be made accessible for applications with nontransparent substrates such as metals. This paper describes the development of extra thin polymer optical fiber narrow fabrics designed to enable curing of structural adhesive joints. Polymer optical fibers (warp) were combined with different low-titer polyester weft yarns in two fabric design types with different primary out-coupling mechanisms: undulation and surface modification of the polymer optical fibers. The effect of yarn properties, thread densities and weave on fabric quality, geometry and lateral light intensity of each type were investigated. Results showed that narrow fabric production within the tight geometric limits required is feasible. Fabrics manufactured with nontextured yarns at low titers and low weft densities exhibited the highest lateral light intensities for the surface modification type fabric. To compensate for intensity loss over fabric length, investigating light coupling from both sides is recommended for this fabric type. For the undulation type fabric, the lateral light intensity characteristics indicated that the high tenacity yarns are promising candidates for the fabrication of low sidelight attenuation fabrics through modulation of the weft density. [ABSTRACT FROM AUTHOR]

This study investigates some novel solitary wave solutions of the perturbed Chen–Lee–Liu ( ℒ ℒ) equation to explain the physical and dynamic behavior of the pulse in optical fiber. The perturbed ℒ ℒ equation is one of the icon models that have been derived from the well-known Schrödinger equation. Two analytical techniques are used to obtain novel solitary wave solutions. Then, using a well-known numerical scheme, these solutions are looked at objectively to figure out why they work. Several graphs in different styles are used to show how the pulse waves in an optical fiber are analyzed and how accurate the analysis is. The scientific novelty of this research is given by explaining the comparison figure out of our results that have been published in some recently published research papers. [ABSTRACT FROM AUTHOR]

A wide range of applications such as healthcare, human comfort, agriculture, food processing and storage, and electronics manufacturing also require fast and accurate measurement of humidity and temperature. Optical fiber-based sensors have several advantages over electronic sensors, and much research has been conducted in this area in recent years. This paper describes the current trends in fiber optic temperature and humidity sensors. The evolution of optical structures aimed at humidity detection is presented, as well as a new design of an optical sensor used for this purpose. The main methods of humidity determination using fiber-optic laser reflection based on Optical fiber humidity sensor (FPI) were analyzed and experimental results were obtained. Based on temperature-sensitive strain variation, a method for temperature determination based on the specific spectral back-reflection effect of fiber Bragg gratings (FBGs) is considered. Experimental analyses were conducted on the light reflection of humiditysensitive agarose using optical fibers based on the Fabry-Perot Interferometer (FPI). It exhibits a good linear response to relative humidity, ranging from 25 % to 95 %. During temperature measurement, the deformation changes of the Fiber Bragg Grating fibers showed excellent performance, ranging from –5 °C to 70 °C. New structures, such as resonators, are being explored to improve the resolution of fiber optic temperature and humidity sensors. In addition, recent studies on polymer optical fibers show that the sensitivity of this type of sensor has not yet been achieved. Thus, materials sensitive to humidity and temperature still need to be investigated to improve sensitivity and resolution. [ABSTRACT FROM AUTHOR]

This paper points out that the commonly used normalized frequency for noncircular dielectric waveguides, which is based on the semiminor axis, causes the cross‐sectional area to vary with the cross‐sectional shape. Consequently, the shape effects described with the conventional normalized frequency are not due to the shape alone but the combined effects of the shape and area. Our numerical results show that the area effect is greater than the shape effect. An improved definition of normalized frequency based on an equivalent radius is proposed in this paper. Conversion formulas to convert from the conventional normalized frequency to the proposed normalized frequency are provided for elliptical and rectangular waveguides. Our numerical results show that the shape effects described by the proposed normalized frequency are free from the area effect. Consequently, the proposed normalized frequency is more accurate than the conventional normalized frequency in describing the shape effect of noncircular dielectric waveguides. [ABSTRACT FROM AUTHOR]

Nanoparticle- (NP-) doped optical fibres show the potential to increase the signal-to-noise ratio and thus the sensitivity of optical fibre strain detection for structural health monitoring. In this paper, our previous experimental/simulation study is extended to a design study for strain monitoring. 100 nm spherical gold NPs were randomly seeded in the optical fibre core to increase the intensity of backscattered light. Backscattered light spectra were obtained in different wavelength ranges around the infrared C-band and for different gauge lengths. Spectral shift values were obtained by cross-correlation of the spectra before and after strain change. The results showed that the strain accuracy has a positive correlation with the relative spectral sensitivity and that the strain precision decreases with increasing noise. Based on the simulated results, a formula for the sensitivity of the NP-doped optical fibre sensor was obtained using an aerospace case study to provide realistic strain values. An improved method is proposed to increase the accuracy of strain detection based on increasing the relative spectral sensitivity, and the results showed that the error was reduced by about 50%, but at the expense of a reduced strain measurement range and more sensitivity to noise. These results contribute to the better application of NP-doped optical fibres for strain monitoring. [ABSTRACT FROM AUTHOR]

Anti-resonant fiber (ARF) works well in a relatively strong magnetic field due to its weak Faraday effect, which results from the fundamental mode mainly transmitting in the air core. Accurately measuring the Faraday effect strength, i.e., the effective Verdet constant, of an ARF determines its applicable scenarios. However, the effective Verdet constant of ARF is ~3 orders of magnitude lower than that of a standard single-mode fiber, which is very difficult to measure. In this paper, we reveal that intermodal interference is the main obstacle to measuring the ultralow effective Verdet constant of ARF and propose using a narrow-band low-coherence light to suppress it. The measured effective Verdet constant of ARF is 0.423 ± 0.005 mrad/T/m at 1550 nm. [ABSTRACT FROM AUTHOR]