Mode Fiber Research Articles

Lactobacillaceae differentially impact butyrate-producing gut microbiota to drive CNS autoimmunity

ABSTRACT Background Short-chain fatty acids (SCFAs), produced by the gut microbiota, are thought to exert an anti-inflammatory effect on the host immune system. The levels of SCFAs and abundance of the microbiota that produce them are depleted in multiple sclerosis (MS), an autoimmune disease of the central nervous system (CNS). The mechanisms leading to this depletion are unknown. Using experimental autoimmune encephalomyelitis (EAE) as a model for MS, we have previously shown that gut microbiomes divergent in their abundance of specific commensal Lactobacillaceae, Limosilactobacillus reuteri (L. reuteri) and Ligilactobacillus murinus (L. murinus), differentially impact CNS autoimmunity. To determine the underlying mechanisms, we employed colonization by L. reuteri and L. murinus in disparate gut microbiome configurations in vivo and in vitro, profiling their impact on gut microbiome composition and metabolism, coupled with modulation of dietary fiber in the EAE model. Results We show that stable colonization by L. reuteri, but not L. murinus, exacerbates EAE, in conjunction with a significant remodeling of gut microbiome composition, depleting SCFA-producing microbiota, including Lachnospiraceae, Prevotellaceae, and Bifidobacterium, with a net decrease in bacterial metabolic pathways involved in butyrate production. In a minimal microbiome culture model in vitro, L. reuteri directly inhibited SCFA-producer growth and depleted butyrate. Genomic analysis of L. reuteri isolates revealed an enrichment in bacteriocins with known antimicrobial activity against SCFA-producing microbiota. Functionally, provision of excess dietary fiber, as the prebiotic substrate for SCFA production, elevated SCFA levels and abrogated the ability of L. reuteri to exacerbate EAE. Conclustions Our data highlight a potential mechanism for reduced SCFAs and their producers in MS through depletion by other members of the gut microbiome, demonstrating that interactions between microbiota can impact CNS autoimmunity in a diet-dependent manner. These data suggest that therapeutic restoration of SCFA levels in MS may require not only dietary intervention, but also modulation of the gut microbiome.

Broadband low-loss polarization-insensitive graphene-integrated photonic crystal fiber modulators in the near-infrared range

The amplitude modulator with the function of converting electric signal to optical amplitude modulation is a key component in high-speed optical communication links. In this paper, we demonstrate a variety of two-dimensional graphene-integrated photonic crystal fiber modulators for efficient near-infrared amplitude modulation with ultra-low insertion loss. Taking the advantages of the perfect total internal reflection of the porous photonic crystal fiber and flexible tunability of the graphene conductivity, the modulation depth of 0.075 dB μm−1 with a low optical loss of 2.13 × 10−4 dB μm−1, a long propagation length of ∼20 mm and polarization-insensitive characteristics in a wide wavelength of 1.3 to 1.8 μm can be achieved. This high-performance modulator may have great potential applications in various high-speed telecommunication, interconnection, and graphene-based integrated photonic systems.

Short wave-near infrared spectroscopy for predicting soluble solid content in intact mango with variable selection algorithms and chemometric model

Mango sweetness is one of the most prominent internal quality constituents that attract consumer's attention. The current common methods used to determine the sweetness of mango have significant disadvantages in that labor-intensive, time-consuming, and damaging techniques. This research aims to predict sweetness in mangoes using short wave-near infrared (SW-NIR) spectroscopy in the ranges 900–1650 nm, along with variable selection algorithms and chemometric model. A total of 120 mango samples were used to collect the spectra using a fibre module SW-NIR spectrometer. The partial least squares (PLS) regression with several spectral preprocessing methods was employed to develop the calibration model, and the best preprocessing technique was selected. The Savitzky–Golay second-derivative preprocessing technique performed better among the other preprocessing techniques with a correlation coefficient of prediction (rpred) of 0.74 and standard error of prediction (SEP) is 0.78 %Brix. After that, two variable selection techniques were used to select effective wavelength variables, including regression coefficient and successive projections algorithm (SPA). For SSC prediction in the range 900–1650 nm, the SPA-PLS model obtained a rpred of 0.78 and SEP of 0.67 %Brix. The current study unequivocally shows that the proposed SW-NIR spectroscopy coupled with a suitable chemometrics method can evaluate mango sweetness nondestructively.

Identifying mode coupling wavelengths in doubly-clad optical fibers with deep learning

Understanding the transmission of light waves in optical fibers and accurately determining the locations of mode coupling are crucial for enhancing the efficiency of optical devices and advancing innovative technologies such as fiber optic sensors, lasers, and modulators. This study utilizes deep learning and image recognition techniques to identify the wavelengths at which mode coupling occurs in optical fibers. Our research findings show that using the ResNet-18 model allows for the rapid and accurate identification of the wavelengths at which mode coupling occurs in optical fibers, as well as the modes involved, achieving an accuracy close to 100 %. We experimented with sampling the dataset at 5 nm and 10 nm intervals to create smaller training and validation sets. Despite the reduced data volume, high accuracy rates were maintained, exceeding 99 % and 97 % respectively. This study provides new insights into the use of deep learning for precise localization of mode coupling points and tracking of transmission modes in optical fibers.

Few-mode optical fiber-based flexible pressure feedback tentacle doped with fluorescence temperature pointer

Abstract In this paper, a flexible fiber pressure feedback whisker is proposed, which consists of a water droplet shaped polydimethylsiloxane (PDMS) elastomer with an embedded balloon shaped few mode fiber. The mechanical sensing performance of the device was analyzed and optimized using a combination of finite element method and beam propagation method (BPM). The built-in cladding corroded few-mode fiber increases pressure sensitivity by more than four times. The collection efficiency of fluorescence signal is improved by cladding corrosion. The PDMS elastomer was doped with upconversion nanoparticles NaYF4:Yb, Er@NaYF4 in order to achieve temperature measurement by fluorescence intensity ratio technology. The combination of fluorescence signal and interference spectrum can not only achieve real-time and accurate pressure detection at different temperatures, but also incorporate fluorescent materials into flexible bionic skin for temperature self-compensation, which has potential application value for the development of bionic fiber micro-nano sensing and control devices.

Scaling up a hollow fibre adsorption unit for on-board CCS applications using a real gasoline engine exhaust

Decarbonising road transport using on-board carbon capture and storage (CCS) is challenged by inherent space and energy limitations. Thus, to be technically and economically viable, robust and compact carbon capture units need to be developed. Hence, in this work, a scaled up hollow fibre adsorption unit was tested downstream of a real 90:10 gasoline-ethanol engine exhaust gas to evaluate its CO2 capture performance after 100 adsorption–desorption cycles. The scaled up hollow fibre adsorption unit consisted of 37 four-channel hollow fibre adsorption units coated with a thin carbon xerogel layer, referred to as the CX-coated hollow fibre module (HFM). It should be noted that this is the first study to report the results of a HFM tested under real conditions over 100 adsorption–desorption cycles and is one of the few studies that reports the desorption step. Furthermore, despite the presence of CO, THC, NOx, and H2O in the exhaust gas, the CX-coated HFM exhibited high CO2 capture stability and mechanical integrity. This was evidenced through the CX-coated HFM obtaining and maintaining an average total capacity of 1.2 mmol/g over 100 adsorption–desorption cycles, and showing no visible signs of deterioration or a loss of mechanical integrity.

Novel mirror-flipped mode permutation technique for long-haul 6-mode transmission

Mode-division multiplexing based on few-mode fibers is expected to overcome capacity limits of current single-mode fiber communications. Mode permutation as an approach for extending transmission reach has attracted great attention. In this paper, we propose a mirror-flipped mode permutation (MFMP) scheme based on newly developed fibers with symmetric differential mode delay (DMD). We demonstrate a 28-GBaud transmission over a 1542-km 6-mode fiber link, which suppresses modal-dispersion impact by 36% and mitigates mode-dependent-loss effect with 3.1-dB Q-factor improvement, compared with the traditional cyclic mode permutation at 1233 km. Then, we experimentally verify that the proposed MFMP works well even using a fiber with a not exactly symmetric group delay distribution. Benefiting from a low DMD in this fiber, we demonstrate a 6-mode PM-QPSK transmission at 25 GBaud with 16-λ channels, extending the transmission distance to 3000 km.

High sensitivity fiber optic current sensor based on Fabry–Perot interferometer manufactured by femtosecond laser

Abstract A novel fiber optic current sensor was prepared based on femtosecond laser processing technology and magnetostrictive material Terfenol-D. Its principle is to use the linear stretching of Terfenol-D material under the action of current to cause linear shift in the sensor spectrum. Firstly, we fabricated Fabry–Perot interferometer (FPI1) using femtosecond laser in a tapered few mode fiber. Then, FPI2 was prepared using the end face of FPI1, quartz capillary, and single-mode fiber. When cascading FPI1 and FPI2, by adjusting the air-cavity length of FPI2, they form a harmonic vernier effect (HVE) sensor. In HVE sensors, FPI1 forms a cantilever beam inside the capillary, which is not affected by axial strain. Therefore, when the axial strain acts on the HVE sensor, the effective length of axial strain increases to the entire length of the quartz capillary, greatly amplifying the strain sensitivity. Finally, the Terfenol-D rod is pasted onto the HVE strain sensor, and the strain change coupled to the strain sensor caused by magnetic field changes is detected by measuring the wavelength shift of the sensor. As the magnetic field strength is directly proportional to the current in the energized coil, this sensor can measure current. The experiment found that the current sensitivity of the sensor is 5.30 nm A−1 in the range of 0.5 A–3.3 A, and the linear fitting coefficient is 0.9926. Additionally, the minimum measurable current change of the sensor is 23 mA. The current sensor is of advantages of high sensitivity, stable sensing performance, compact structure, easy fabrication and low cost, meaning wide application prospect.

Innovative concepts in diet therapies in disorders of gut-brain interaction.

Diet therapy in disorders of gut-brain interaction (DGBI) is rapidly advancing, with accumulating evidence to support two innovative therapies-manipulation of dietary fibers and enzyme supplementation-that target specific DGBI pathophysiology and modulate digestion. Dietary fibers escape digestion in the upper gastrointestinal tract and can influence gut function by impacting digestion, improving laxation, and interacting with the microbiota. A more nuanced understanding of different fiber types and their ability to impact gut function in highly specific ways has shown that fibers can impact distinct gut symptoms and pathophysiology. By considering their functional characteristics of bulking, gel-forming, and fermentability, restriction or supplementation of specific fibers can offer clinical value in DGBI. Similarly to fiber specificity, emerging evidence suggests that supplemental digestive enzymes may be targeted to known food triggers with consideration that enzymes are substrate specific. Limited evidence supports use of lactase to target lactose, and α-galactosidase to target galacto-oligosaccharides. Application of enzymes during manufacturing of food products may prove to be an additional strategy, although evidence is scant. Both innovative therapies may be utilized in isolation or in combination with other diet and nondiet therapies. Implementation can be guided by the principles that fiber modulation can be targeted to specific symptomology or requirement for alterations to gut function, and digestive enzymes can be targeted to known food triggers. This review aims to summarize recent literature of these two innovative concepts and provide practical suggestions for their implementation in clinical practice.

Study on joint effects of modal dispersion, mode-dependent loss and noise by unified density-matrix formalism

We generalize the density-matrix formalism to provide a simple and unified framework for the study of modal dispersion (MD), mode-dependent loss (MDL) and noise in mode-division-multiplexing communication systems. Fundamental concepts and formulas in the original formalism are generalized, while new elements and associated equations are introduced and/or derived. Due to the ability of the density operator to characterize partially-coherent fields, the generalized density-matrix formalism is particularly useful for analyzing the field propagation in presence of noise. Combining the unified density-matrix formalism and the stochastic-process theory, we conduct detailed numerical simulation and analysis on the modal properties of a randomly-perturbed 6-mode fiber with loss and noise. We find that although the MDL only slightly affects the statistics of the group delays, it can cause significant non-orthogonality among the principal modes, which might induce extra crosstalk and temporal spreading in the signal pulses. Furthermore, with the coherency of fields in the fiber being reduced by the noise, the MDL can induce substantial fluctuation in the field coherency even though it does not significantly affect the averaged field coherency.

Frequency diversity of modal dispersion in mode-division multiplexing systems from strong to weak coupling regimes

Based on a statistical model applicable to all mode-coupling regimes and a trace covariance function of the group-delay matrix for characterizing the modal-dispersion correlation, we study the frequency diversity of modal dispersion in randomly-perturbed mode-division multiplexing optical communication systems. Particularly, we conduct detailed numerical simulation and analysis on the statistical properties of the modal dispersion in a 6-mode fiber under random perturbation. The results show that, at two frequencies of sufficiently large difference, while the modal dispersion eventually gets uncorrelated in the strong coupling regime, there remains a significant amount of “residual” correlation in the weak coupling regime. Also, we find that, although the typically-assumed frequency-domain ergodicity is reasonably valid in the strong coupling regime, it clearly fails in the weak coupling regime. The crossover from the strong to weak coupling regimes is also quantitatively investigated.

Performance modulation and optimization of PE fiber reinforced 3D-printed geopolymer

This paper aims to develop an environmentally friendly and low-carbon geopolymer for 3D printing, which has excellent mechanical and rheological performance. The effect of ground granulated blast furnace slag (GGBS), NaOH and sand on mechanical strengths, 3D printing performance and rheological behavior was investigated to determine the optimum mix proportion for 3D-printed geopolymer. Moreover, polyethylene (PE) fibers were introduced to reinforce the performance of 3D-printed geopolymer. Results show that when the ratio of GGBS, NaOH and sand is 1:0.13:2.67, geopolymer exhibits superior mechanical, 3D printing and rheological properties. Increasing the dosage of GGBS and sand leads to an overall increase in the yield stress but a decrease in the consistency coefficient, indicating that it benefits the stacking and fluidity performance of 3D-printed geopolymer. However, with an increase of NaOH content, the stacking performance increases while the fluidity decreases. Although increasing NaOH and sand content benefits the viscosity recovery performance, an increase in GGBS content has an opposite effect. Incorporating PE fibers significantly increases the flexural strength with an increase of up to 27.8 % and 21.3 % in 7-d and 28-d flexural strength, respectively, given a PE fiber volume of 0.6 %. Increasing the volume of PE fibers leads to a significant rise in the stacking performance but a reduction in the fluidity. Furthermore, adding PE fibers negatively affects the geopolymerization but benefits the hydration process given an increase of Si/Al and Si/Ca ratio identified in PE fiber reinforced 3D-printed geopolymer.

Extra-cavity modulation of a chirped Gaussian bisoliton

Optical solitons can find important applications in optical fiber communication systems. Here, we simulate extra-cavity modulation of a chirped Gaussian bisoliton in a 1 μm wavelength band. Several different soliton parameters are varied (including the amplitude ratio and time delay of orthogonal components, the projection angle, phase difference, pulse chirps and propagation distances), to effectively change the optical spectra and pulse shapes of the initial input chirped Gaussian bisoliton. For example, when the two branches in the optical fiber modulation system have the same or different fiber lengths, the modulated chirped Gaussian bisoliton will show obviously different properties in the time domain for orthogonally polarized components, while the corresponding optical spectra have no obvious differences. The simulation results reveal the effects of extra-cavity modulation of the chirped Gaussian bisoliton, which further explores the field of soliton shaping out of a fiber laser cavity.

Effect of different washing processes, twill direction and yarn types on the performance properties of denim fabrics

This study aims to investigate the effects of different washing processes, twill directions, and yarn types on the performance properties of denim fabrics. For this purpose, 100% cotton elastane, 85% cotton/15% Modal elastane, and 85% cotton/15% Tencel elastane including denim fabrics were produced with two different weaves (3/1 Z and 3/1 S), and four different industrial washing operations were applied to these denim fabrics. In addition, untreated fabrics (not industrially washed) were used to compare the performance of the fabrics before and after industrial washing. The highest warp-breaking strength values were observed in the rinse-washed fabrics, whereas the highest shrinkage, elasticity, and rubbing fastness values were observed in the bleach-washed fabrics. In addition, it can be said that industrial washing processes reduce the growth values of untreated fabrics and reduce the bagging during use. Although the crystallisation degree of Tencel fibre is higher than that of Modal fibre, it was concluded that the use of Modal fibre with cotton increased the strength values. In contrast, the use of Tencel fibre with cotton increased the elasticity and rubbing fastness values of the denim fabrics.

High Verdet constant of Tb2O3-doped TiO-B2O3-Al2O3-Na2O magneto-optical glass

Tb-doped magneto-optical (MO) glass is widely used in fiber optics, optical isolators, and modulators. However, only the paramagnetic Tb3+ ions exhibit significant MO effects, whereas the diamagnetism Tb4+ ions suppress the MO effects. Therefore, the valence state control of Tb ions is very critical to optimize MO performance. Here, a reduction strategy was introduced to adjust the Tb valence in glass to achieve the high MO effect. The TiO, which has low valence Ti2+ ions and good reducibility, was used to suppress the oxidation of Tb3+ to Tb4+ ions. In the TiO-B2O3-Al2O3-Na2O glass, 10 mol% TiO can increase the Verdet constant at 650 nm by 19%. With the further increase in Tb2O3 concentration, the Verdet constant reaches a high value of 117 rad/(T·m) at 650 nm, which is close to the Verdet constant of TGG crystal (121 rad/(T·m)). This work provides a new approach to increase the Verdet constant of MO glass.

Progress in module design for membrane distillation

There have been tremendous advances in membrane distillation (MD) since the concept was introduced in 1961: new membrane designs and process configurations have emerged, and its commercial viability has been evaluated in several pilot-scale studies. However, its high energy consumption has hindered its commercialization. One of the most promising ways to overcome this obstacle is to develop more energy-efficient membrane modules. The MD research community has therefore developed diverse new module configurations for hollow fiber and flat sheet membranes that increase the thermal energy efficiency of MD by minimizing thermal polarization, increasing mass transfer across the membrane, and improving heat recovery from the condensed vapor. This review summarizes the progress made in the design of hollow fiber and flat sheet membrane modules for MD applications. It begins with a brief introduction to MD and its configurations before describing developments in module fabrication and highlighting key areas where further research is needed.

Design of low crosstalk homogeneous multicore few mode fiber for future high-capacity optical transmission

Many researches are diligently striving to develop a multi-core optical fiber with minimal signal distortion and reduced issues. The current study proposed few designs for homogeneous multicore few mode fiber which is characterized by the combination of high index ring and trench. This study also added four air holes surrounding each core. We considered pure silica for both the outer clad and the inner clad of the fiber. To calculate the crosstalk, a two-core model was used and the mode coupling coefficient was determined using coupled-mode and couple-power theory. For the current work we considered only the fundamental mode (LP01) to compute the crosstalk between neighboring cores. The proposed structure was simulated using the wave optics module of COMSOL Multiphysics (Version 6.1), a well-known commercial software tool based on finite element method (FEM). MATLAB (Version R2018a) was used to calculate the mode coupling coefficient and crosstalk after extracting the mode field data from COMSOL. Obtained results revealed that the proposed structure can offer lower crosstalk which was attractive for future high-capacity fiber optic communication using multicore fiber technology.

Influence of geometry passive Q-switch based on a nanopowder-polymer on the characteristics of an erbium ring fiber laser

The presented work shows an influence of geometry passive Q-switch based on a nanopowder-polymer on the characteristics of an erbium ring fiber laser. The saturable absorber Bi2Te3 was applied to two types of specially prepared samples of thinned sections of optical fiber, and the resulting structures were built into the ring circuit of an erbium fiber laser. In the first case, the surface of the light guide segment was thinned by chemical etching, and in the second, by mechanical grinding. For the first time, the time-domain optical reflectometry technique was used to control the quality of the resulting sample surface and the resulting losses. For a more complete comparison, a set of different optical splitters was used, providing a change in the feedback coefficient in the resonator from 5 to 95 %. A study in the mode of passive Q-switching using polarized light showed that for both types of modulators there are optimal ratios of the amount of energy output from the resonator to obtain the highest values of the average generation power. The d-shape fiber modulator allows mode-locking to be observed without any additional changes to the laser circuit. The pulse duration in this case was 5 ns with a repetition rate of 4 MHz. A Q-switch based on a chemically thinned fiber segment made it possible to obtain narrower pulses in Q-switching mode (up to 700 ns at 38 kHz), a stable peak position in the transmission spectrum, and an average power of 34 mW.

Optical-related properties and characterization of some textile fibers using near-infrared spectroscopy

Abstract When light falls on the fiber surface, it is absorbed, reflected, or refracted. These three phases of incident light determine, to a great extent, the behavior of lustre of major textile fibers. This article sheds light upon the behavior of some textile fibers, namely, polyethylene terephthalate, cotton, viscose, bamboo, tencel, and modal fibers, in terms of their reflectance percentages in the ultraviolet regions. Also, the direct and indirect band-gap energies of the used textile fibers were also investigated. The findings of this study revealed the significant differences among these used textile fibers in relation to their optical properties. Also, the chemical composition of the used textile fibers was easily identified using near-infrared spectroscopy. Finally, the findings of this study revealed that the used textile fibers are considered good insulators.

Generation of THz radiation through molecular modulation in hydrogen-filled hybrid anti-resonant fibers.

We study the generation of narrowband terahertz (THz) pulses by stimulated Raman scattering and molecular modulation in hydrogen-filled hybrid hollow-core fibers. Using a judicious combination of materials and transverse structures, this waveguide design enables simultaneous confinement of optical and THz signals with reasonably low attenuation, as well as high nonlinear overlap. The THz pulses are then generated as the second Stokes band of a ns-long near-infrared pump pulse, aided by Raman coherence waves excited in the gaseous core by the beat-note created by the pump and its first Stokes band. Optimization of the fiber characteristics facilitates phase matching between the corresponding transitions and coherence waves while avoiding coherent gain suppression, resulting in potential optical-to-THz conversion efficiencies up to 60%, as confirmed by rigorous numerical modelling under ideal zero-loss conditions. When the current optical material constraints are considered, however, the attainable efficiencies relax to 0.2%, a still competitive value compared to other systems. The approach is in principle power and energy scalable, as well as tunable in the 1-10 THz range without any spectral gaps, thereby opening new pathways to the development of fiber-based THz sources complementary to other mature technologies such as quantum cascade lasers.