Fiber Array Research Articles

Interference fading suppression with fault-tolerant Kalman filter in phase-sensitive OTDR

A multi-sensor information fusion algorithm based on fault-tolerant Kalman filter is proposed in phase-sensitive optical time-domain reflectometer (Φ-OTDR) system, for achieving fading-free distributed vibration sensing. Firstly, a fault-tolerant dual-core complementary array model is designed. The Rayleigh scattering signal denoising, and vibration existence judgment of localization points are carried out to obtain the differentiated frequency demodulation results of the sensing points of the dual-core fiber array. Then a fault-tolerant control strategy is used to determine the sensor weight coefficients and vibration judgment coefficients during data fusion processing, and array data fusion is carried out based on time series data using Kalman filter to realize error value identification and filling. The advantage of this method is the combination of redundant data in a complementary way to improve the system stability. The frequency response ranges from 10 Hz to 2400 Hz and the localization accuracy is 98.33%. The influence of key parameters on the frequency demodulation performance of fault-tolerant Kalman filter is discussed, and a standard deviation of 14.6 Hz and an average error of 7.6 Hz are obtained. The demodulation frequency data matrix obtained by the classical demodulation method has a demodulation error probability of 89.18%, which proves the widespread existence of demodulation errors in vibration signals. The fusion error of demodulation frequency is reduced to 0.25 Hz, the frequency demodulation accuracy reaches 100%, and the demodulation error caused by interference attenuation can be completely eliminated. This system based on fault-tolerant Kalman filter has the characteristics of simple multiplexing structure, interference fading resistance and stable demodulation performance.

Simultaneous and sensitive detection of methylparaben and its metabolites by using molecularly imprinted solid-phase microextraction fiber array technique

BackgroundMethylparaben (MP), a commonly used antibacterial preservative, is widely used in personal care products, foods, and pharmaceuticals. MP and its metabolites are easy to enter the water environment, and their exposure and accumulation have negative effects on the ecological environment and human health, and have endocrine disrupting activity and potential physiological toxicity. It is still the primary issue of environmental analysis and ecological risk assessment to develop simple and reliable methods for simultaneous sensitive detection of these compounds in environmental water. ResultsIn this paper, a flexible molecularly imprinted fiber array strategy is proposed for simultaneous enrichment and detection of trace MP and its four main metabolites. The experimental results showed that the three-fiber imprinted fiber array constructed by MP imprinted fiber had the best effect on the simultaneous enrichment of these five target analytes. The enrichment capacity of the imprinted fiber array was 214–456 times, 314–1201 times and 38–685 times that of commercial PA, PDMS and PDMS/DVB fiber arrays, respectively. The limit of detection (LOD) of this method was 0.033 μg L−1. The spiked recovery rate was 86.78–113.96 %, and RSD was less than 9.17 %. In addition, this molecularly imprinted SPME fiber array has good stability, long service life and can be used repeatedly at least 100 times. SignificanceThis molecularly imprinted fiber array strategy can flexibly assemble different molecularly imprinted SPME fibers together, effectively improve the enrichment ability and detection sensitivity, and achieve simultaneous selective enrichment and detection of several analytes. This is an easy, efficient and reliable method for monitoring several trace analytes simultaneously in intricate environmental matrices.

Development of a plastic scintillating optical fibers array dosimeter for radiobiology

In this work a detector prototype built as an array of Scintillating Plastic Optical fibers (SPOFs) is presented. The primary aim of this detector is to improve spatial resolution, provide real-time dose mapping and a tissue equivalent detector in radiobiology experiments. Details on the design and construction are provided along with the initial tests carried out using low-energy X-ray and electrons from a 90Sr source. Regarding the design and construction of the detector, the mechanical design of the irradiation box is presented and the Quality Assurance (QA) the optical fiber arrays were subjected to is discussed. The QA measurements show that the alignment of the optical fibers is within acceptable tolerances for dose readout. After the detector assembly, correction factors for each fiber were extracted from tests using a collimated X-ray beam. Special care was taken to ensure that each fiber is submitted to the same dose. Broad field tests show that the measurements are reproducible to within 3 %. Potential innovative features of this system for radiobiological experiments are discussed as well as the future follow-up of the prototype.

Lignocellulosic-Based/High Density Polyethylene Composites: A Comprehensive Study on Fiber Characteristics and Performance Evaluation

Lignocellulosic-based polymer composites have gained significant interest due to their ‘’green’’ character as a response to environmental concerns. A diverse array of lignocellulosic fibers is utilized, depending on fiber dimensions, chemical composition, moisture content, and the fiber–matrix interface. The aim of this study is to establish an alternative standardized methodology, aimed at comparatively estimating the performance of polymer composites through the examination of individual plant fibers. The fibers studied are ramie, hemp, flax, and kenaf, and HDPE-based corresponding composites were analyzed for their performance across various fiber-content levels (10, 20, and 30 wt.%). It was found that kenaf showcases the largest average fiber diameter, succeeded by hemp, ramie, and flax. Additionally, ramie and kenaf exhibit elevated levels of crystallinity, suggesting increased cellulose content, with kenaf having the lowest crystallinity index among the fibers compared. Based on Thermogravimetric analysis, ramie displays the lowest moisture content among the examined fibers, followed by hemp, flax, and ultimately kenaf, which is recorded to have the highest moisture content, while, similarly, ramie exhibits the lowest mass loss at the processing temperature of the corresponding composites. Composites containing fibers with smaller diameters and higher crystallinity indexes and lower moisture absorptions, such as ramie and hemp, demonstrate superior thermal stability and exhibit increased Young’s modulus values in their respective composites. However, poor interfacial adhesion affects mechanical performance across all composites. Understanding fiber morphology, inner structure, and thermal stability is important for developing new composite materials and optimizing their selection for various applications.

Thermal degradation and fire retardant behaviour of natural fibre reinforced polymeric composites- A comprehensive review

In this comprehensive review, we dive into the potential of natural fibre composites, tracing their historical use spanning three millennia and their recent incorporation into polymer matrices. Various natural fibres, including flax, hemp, jute, and more, have been explored as potential reinforcements due to their renewable nature and environmental appeal. Moreover, these fibers are gaining traction in industries such as automotive and packaging. Leveraging abundant agricultural waste such as, wheat husk, rice husk, straw, and hemp fibre into commercially viable fibre-reinforced polymer composites. A thorough summary is given in this article of the diverse array of natural fibers, their current research status, encompassing properties, processing techniques, filler materials on structural factors, thermogravimetric analysis, dynamic mechanical performance under thermal loading, fire retardant behaviour, cone calorimetric analysis and various other applications, all while referencing the latest developments in the field, exploring a sustainable future with natural fibre composites. Furthermore, the difficulties associated with natural fibre-reinforced composites, including their vulnerability to humidity, fire retardancy and compliance with fibre matrices, are examined. This paper summarizes the complex field of natural fibre composites and covers several thermal stability-related appearance.

Structural diversity of crustacean exoskeletons and its implications for biomimetics.

The crustacean cuticle is a biological composite material consisting of chitin-protein fibres in a mineralized matrix. Recent research has revealed a surprising range of fibre architectures and mineral compositions of crustacean skeletal structures adapted to various mechanical demands. It is becoming increasingly clear that the organic fibres in the cuticle may be organized in patterns differing from the standard twisted plywood model. Observed fibre architectures in protruding skeletal structures include longitudinal and circular parallel fibre arrays. Skeletal minerals often include calcium phosphates in addition to calcium carbonates. Furthermore, skeletal properties are affected by protein cross-linking, which replaces mineralization as a stiffening mechanism in some structures. Several common structural motifs, such as the stiffening of the outer skeletal layers, the incorporation of non-mineralized cuticle in exposed structures, and interchanging layers of parallel fibres and the twisted plywood structure, can be identified in skeletal elements with similar functions. These evolutionary solutions have the potential for biomimetic applications, particularly as manufacturing technologies advance. To make use of this potential, we need to understand the processes behind the formation of the crustacean exoskeleton and determine which features are truly adaptive and worth mimicking.

Manufacturing of bioinspired Bouligand structures using ultrasound assisted 3D printing

Materials with bioinspired Bouligand structures provide a new approach to explore isotropic fiber-reinforced composites. However, it is challenging to manufacture composites with various fibers along with a three-dimensional helical structure. In this work, to accomplish the alignment of a three-dimensional (3D) helical structure of fibers in a composite material, an acoustically aligned fiber technology was incorporated with a rotating mechanism in a stereolithography 3D printer. Firstly, the formation process of acoustic standing wave was simulated and the relationship between standing wave parameters and planar line arrays was then established. Secondly, Bouligand composites with various parameters were fabricated using an acoustic-assisted 3D printing technology and the effect of the angle between the interlayer fiber arrays on the mechanical properties was experimentally measured. Finally, heat sink and meniscus structures with Bouligand structure were fabricated using carbon nanofiber and glass nanofiber, respectively. The 3D printing processing method integrating acoustic alignment technology and rotating mechanism provides a new method for fabrication of composite materials with complex fiber structures.

Millet production, challenges, and opportunities in the Asia-pacific region: a comprehensive review

Global warming, water scarcity, population growth, rising food prices, urbanization, and other socio-economic factors pose significant threats to agriculture and food security in the 21st century. This situation is particularly grave for low-income individuals in the Asia-Pacific region. To tackle this challenge and eradicate hunger and poverty, it is imperative for scientists to explore alternative food sources, covering all stages from production through processing to consumption. Cereal grains serve as a crucial food source and hold substantial importance in human diets. Therefore, revamping the food system becomes crucial to achieve food and nutritional security. A pragmatic approach toward reaching this goal involves ensuring universal access to affordable, wholesome, and nourishing food through the utilization of millets—nutrient-dense grains (often referred to as Nutri-cereals) that offer a rich array of vital macronutrients, micronutrients, carbohydrates, protein, dietary fiber, lipids, and phytochemicals. Leveraging these grains holds the potential to significantly alleviate the challenges of food insecurity and malnutrition. Millet, a drought-resistant grain, constitutes a primary source of carbohydrates and proteins for populations residing in semi-arid regions of Africa and Asia. Given its crucial contribution to national food security and potential health advantages, there is a growing focus among food scientists. Additionally, the United Nations designated 2023 as the International Year of Millet, underscoring its importance. This article delves into various methods of production and processing, highlighting opportunities to enhance the production and nutritional qualities of millet. We attribute millets to inadequate rainfall distribution, poor crop management high prices of farm inputs such as fertilizer and pesticides and low adoption of improved varieties by the farmers. It also outlines the constraints, challenges, and future prospects associated with promoting millet as a viable food source for the burgeoning population. Despite the promise that millets hold, they have not received adequate research attention. Therefore, increased research efforts on integrating genomics in genome-wide marker-trait association are imperative, encompassing germplasm collection, protection, evaluation, consumption patterns, development of high-yielding cultivars, processing techniques, and policy interventions. Such initiatives are necessary to bolster the cultivation of millets and harness their potential to address the escalating global food challenge.

Time-delay fourier transform spectrometer for high-speed spectral measurement

In the field of optics, there exist numerous chaotic processes like dissipative soliton dynamics, random laser generation, and laser scattering. It's very challenging to accurately capture the dynamics of these stochastic processes from the wavelength perspective with traditional spectrometers due to their slow signal integration speeds. Here, we propose a new approach, named time-delay Fourier transform spectrometer (TDFTS), to characterize the spectra of laser pulses with durations ranging from fs to ns with high speeds. Based on a fiber array with different lengths to impose frequency-dependent time delay, TDFTS efficiently maps the spectral distribution of light pulses to the temporal domain, and the spectrum can thus be detected with a photodiode and an oscilloscope. In experimental operation, the TDFTS provides spectral acquisition speeds up to 56 MHz frame rates and a bandwidth of tens of nanometers, while keeping comparable fidelity to traditional grating-scan spectrometers. While its spectral resolution of the current configuration is ∼0.1 nm, it can be further improved to 0.001 nm through optimizing the system. Based on its high speed, high spectral resolution, broad-bandwidth coverage, and compact configuration, TDFTS can be used to monitor nanosecond-scale spectral dynamics of non-repetitive optical processes.

Laser welding of fiber array units.

We report the results of fabricating fiber array unit (FAU) connectors using a near IR laser welding process, locking fibers in proper position on planar glass substrates and forming strong glass-to-glass bonds, followed by final assembly using lower coefficient of thermal expansion (CTE) epoxies. A thin metal film deposited on the glass substrate provides the absorption required to attain interfacial temperatures suitable for glass-to-glass bonding. This method allows the elimination of dedicated expensive V-groove plates while still maintaining very good fiber placement accuracy. The use of epoxy is minimized to simply securing macro packaging components and protecting fibers from environmental pressure, temperature, and humidity variation. The thermal expansion properties of the epoxy used were essential for the long-term FAU reliability.

Harvesting Silk Fibers from Plodia interpunctella: Role of Environmental Rearing Conditions in Fiber Production and Properties.

Silk fibers are produced by a wide variety of insects. The silkworm Bombyx mori (Bombyx) was domesticated because the physical properties of its silk fibers were amenable to the production of fine textiles. Subsequently, engineers have regenerated silk fibroin to form biomaterials. The monocular focus on Bombyx silk has underutilized the expanse of diverse silk proteins produced by more than 100,000 other arthropods. This vast array of silk fibers could be utilized for biomedical engineering challenges if sufficient rearing and purification processes are developed. Herein, we show that the moth, Plodia interpunctella (Plodia), represents an alternative silk source that is easily reared in highly regulated culture environments allowing for greater consistency in the silk produced. We controlled the temperature, resource availability (larvae/gram diet), and population density (larvae/mL) with the goal of increasing silk fiber production and improving homogeneity in Plodia silk proteins. We determined that higher temperatures accelerated insect growth and reduced life cycle length. Furthermore, we established initial protocols for the production of Plodia silk with optimal silk production occurring at 24 °C, with a resource availability of 10 larvae/gram and a population density of 0.72 larvae/mL. Population density was shown to be the most prominent driving force of Plodia silk mat formation among the three parameters assessed. Future work will need to link gene expression, protein production and purification, and resulting mechanical properties as a function of environmental cues to further transition Plodia silk into regenerated silk fibroin biomaterials.

Next-generation endoscopic probe for detection of esophageal dysplasia using combined OCT and angle-resolved low-coherence interferometry.

Angle-resolved low-coherence interferometry (a/LCI) is an optical technique that enables depth-specific measurements of nuclear morphology, with applications to detecting epithelial cancers in various organs. Previous a/LCI setups have been limited by costly fiber-optic components and large footprints. Here, we present a novel a/LCI instrument incorporating a channel for optical coherence tomography (OCT) to provide real-time image guidance. We showcase the system's capabilities by acquiring imaging data from in vivo Barrett's esophagus patients. The main innovation in this geometry lies in implementing a pathlength-matched single-mode fiber array, offering substantial cost savings while preserving signal fidelity. A further innovation is the introduction of a specialized side-viewing probe tailored for esophageal imaging, featuring miniature optics housed in a custom 3D-printed enclosure attached to the tip of the endoscope. The integration of OCT guidance enhances the precision of tissue targeting by providing real-time morphology imaging. This novel device represents a significant advancement in clinical translation of an enhanced screening approach for esophageal precancer, paving the way for more effective early-stage detection and intervention strategies.

Design of Self-Matching Photonic Lantern for High-Order Transverse-Mode Laser Systems

High-order transverse-mode lasers have important potential application value in many fields. To address the current issue of the limited controllability of modes in high-order transverse-mode lasers, we have designed a self-matching photonic lantern (SMPL). The SMPL is formed by introducing a few-mode fiber into the input fiber array of the traditional photonic lantern. The parameters of the few-mode fiber match those of the tapered few-mode port of the SMPL; thus, it can transmit high-order modes in a closed loop. The designed SMPL exhibits dual-band multiplexing characteristics at 980/1550 nm, manifesting specifically as high-order mode selectivity excitation at 980 nm and mode preservation at 1550 nm. These characteristics have been validated through simulation and preliminary experiments. The SMPL is designed for constructing all few-mode fiber ring cavity lasers, enabling the pumping of the 980 nm fundamental mode to high-order modes and the transmission of multiple high-order transverse-mode lasers at 1550 nm in a closed loop. The proposed SMPL extends the configuration and functionality of the photonic lantern family, offering a flexible and effective approach to facilitate the generation of multiple high-order transverse-mode lasers. The SMPL combined with fiber laser systems could effectively broaden communication channels and enhance communication bandwidth. It also holds significant value in optical sensing, high-resolution imaging, laser micro-processing, and other fields.

The Design of a Fiber-Coupling Micro-Lens Array for an M × N Wavelength-Selective Switch.

The M × N port wavelength-selective switch (WSS) is a crucial device used for Reconfigurable Optical Add/Drop Multiplexors and optical switching nodes in optical communication systems. The primary function of an M × N port WSS is to simultaneously transmit and switch multiple input optical signals from input fiber ports to output fiber ports through spatial light coupling. The port array module in a WSS that is responsible for coupling the spatial beam with the fiber determines the important parameters of the M × N port WSS, such as the number of input/output ports and insertion loss. In this paper, VirtualLab Fusion software 2023.1 (Build 1.558), as a powerful physical optics simulation tool, is used to design and optimize a silicon micro-lens array that can achieve the high-precision coupling of a fiber array with a pitch of 1143 μm. Finally, the designed micro-lens is manufactured and experimentally demonstrates its good beam focusing ability with a 3 dB insertion loss. The designed micro-lens array coupling system, which delivers 28 focused spots of approximately 1mm in size (the beam has a 1/e2 diameter) after transmitting a distance of around 300 mm, effectively extends the number of WSS ports. This design method of the micro-lens array significantly amplifies the port count of the M × N port wavelength-selective switch, effectively expanding it to encompass an impressive 28 × 28 ports.

Preparation, Microstructure and Thermal Properties of Aligned Mesophase Pitch-Based Carbon Fiber Interface Materials by an Electrostatic Flocking Method.

The mesophase pitch-based carbon fiber interface material (TIM) with a vertical array was prepared by using mesophase pitch-based short-cut fibers (MPCFs) and 3016 epoxy resin as raw materials and carbon nanotubes (CNTs) as additives through electrostatic flocking and resin pouring molding process. The microstructure and thermal properties of the interface were analyzed by using a scanning electron microscope (SEM), laser thermal conductivity and thermal infrared imaging methods. The results indicate that the plate spacing and fusing voltage have a significant impact on the orientation of the arrays formed by mesophase pitch-based carbon fibers. While the orientation of the carbon fiber array has a minimal impact on the shore hardness of TIM, it does have a direct influence on its thermal conductivity. At a flocking voltage of 20 kV and plate spacing of 12 cm, the interface material exhibited an optimal thermal conductivity of 24.47 W/(m·K), shore hardness of 42 A and carbon fiber filling rate of 6.30 wt%. By incorporating 2% carbon nanotubes (CNTs) into the epoxy matrix, the interface material achieves a thermal conductivity of 28.97 W/(m·K) at a flocking voltage of 30 kV and plate spacing of 10 cm. This represents a 52.1% increase in thermal conductivity compared to the material without TIM. The material achieves temperature uniformity within 10 s at the same heat source temperatures, which indicates a good application prospect in IC packaging and electronic heat dissipation.

Fabrication of Zigzag Parylene Nanofibers in Liquid Crystals with Electric Field-Induced Defect Structures.

Liquid crystals (LCs) have been adopted to induce tunable physical properties that dynamically originated from their unique intrinsic properties responding to external stimuli, such as surface anchoring condition and applied electric field, which enables them to be the template for aligning functional guest materials. We fabricate the fiber array from the electrically modulated (in-plain) nematic LC template using the chemical vapor polymerization (CVP) method. Under an electric field, an induced defect structure with a winding number of -1/2 contains a periodic zigzag disclination line. It is known that LC defect structures can trap the guest materials, such as particles and chemicals. However, the resulting fibers grow along the LC directors, not trapped in the defects. To show the versatility of our platform, nanofibers are fabricated on patterned electrodes representing the alphabets 'CVP.' In addition, the semifluorinated moieties are added to fibers to provide a hydrophobic surface. The resultant orientation-controlled fibers will be used in controllable smart surfaces that can be used in sensors, electronics, photonics, and biomimetic surfaces.

Experimental Investigation on a Relativistic Gyrotron Driven by a Carbon Fiber Array Cathode

Experimental Investigation on a Relativistic Gyrotron Driven by a Carbon Fiber Array Cathode

Ultra-miniature dual-wavelength spatial frequency domain imaging for micro-endoscopy.

There is a need for a cost-effective, quantitative imaging tool that can be deployed endoscopically to better detect early stage gastrointestinal cancers. Spatial frequency domain imaging (SFDI) is a low-cost imaging technique that produces near-real time, quantitative maps of absorption and reduced scattering coefficients, but most implementations are bulky and suitable only for use outside the body. We aim to develop an ultra-miniature SFDI system comprising an optical fiber array (diameter 0.125mm) and a micro camera ( package) to displace conventionally bulky components, in particular, the projector. First, we fabricated a prototype with an outer diameter of 3mm, although the individual component dimensions could permit future packaging to a diameter. We developed a phase-tracking algorithm to rapidly extract images with fringe projections at three equispaced phase shifts to perform SFDI demodulation. To validate the performance, we first demonstrate comparable recovery of quantitative optical properties between our ultra-miniature system and a conventional bench-top SFDI system with an agreement of 15% and 6% for absorption and reduced scattering, respectively. Next, we demonstrate imaging of absorption and reduced scattering of tissue-mimicking phantoms providing enhanced contrast between simulated tissue types (healthy and tumour), done simultaneously at wavelengths of 515 and 660nm. Using a support vector machine classifier, we estimate that sensitivity and specificity values of are feasible for detecting simulated squamous cell carcinoma. This device shows promise as a cost-effective, quantitative imaging tool to detect variations in optical absorption and scattering as indicators of cancer.

Generating high-dimensional entanglement using a foundry-fabricated photonic integrated circuit

We present a silicon photonic integrated circuit (PIC) designed to generate high-dimensional (HD) entanglement across four discrete waveguide path modes. Our PIC is foundry fabricated and fully packaged with electrical wirebonds and an epoxy bonded fiber array. We performed a partial characterization of our system’s density matrix by demonstrating spectral indistinguishability of photon pairs, measuring the joint coincidence distribution of photon pairs across all pairs of output modes, and measuring the coherences of different mode pairs using two-photon interference. Using a quantitative entanglement witness, we have determined that our system generates at least 1.45 ± 0.15 ebits of HD photonic entanglement.

Ultrahigh-speed phase demodulation of a Fabry-Perot sensor based on fiber array parallel spectral detection.

An ultrahigh-speed phase demodulation system was designed for the Fabry-Perot (F-P) interferometric sensor based on fiber array parallel spectral detection. A high-power amplified spontaneous emission (ASE) source served as the broadband detection light. The spectrum generated by the dispersion of the F-P interference light through an arrayed waveguide grating (AWG) was incident into the fiber array and was detected in parallel by 48 photodiodes. The 48-channel signals were acquired synchronously and processed in real time to achieve a phase demodulation for the F-P cavity at 200 kHz. As a result, a low-resolution spectral detection and demodulation system was constructed with high speed. The length demodulation range of the F-P cavity was 60-700 µm, and the demodulation resolution was as high as 0.22 nm. The designed high-sensitivity demodulator is expected to be used for ultrasonic and high-frequency vibration detection.