Microstructured Fiber Research Articles

Effect of short carbon fibers on the thermal conductivities of Csf/AZ91D composites

Developing metal matrix composites with lightweight and high thermal conductivities (TCs) to realize high-efficiency thermal management is of great significance. Herein, a strategy for preparing short carbon fiber preform without any chemical binder through the application of vacuum filtration is proposed. High in-plane and nearly unaltered out-plane thermal conductive magnesium matrix composites with short carbon fibers have been prepared by the independently developed liquid-solid extrusion following the vacuum infiltration (LSEVI) technique. The in-plane TCs of the composites reaches 72.16 W·(m·K)−1, a 50.3% enhancement compared to the matrix. The microstructures of the carbon fibers and magnesium matrix before and after the fabrication processing are characterized using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy (RS). The composites display attractive thermal properties and this work provides an efficient approach to prepare short fiber-related thermal conductive metal matrix composites with a refined thermal management capacity.

Mineral-impregnated carbon-fiber (MCF) composites made with differently sized fly-ash geopolymers for durable light weight and high temperature applications

For a wide application of carbon-fiber reinforcement in large-scaled, lightweight construction, mineral-impregnated carbon-fiber (MCF) composites provide a promising alternative to rebar or reinforcement made of non-metallic fibers and polymer matrix. The penetration ability of the aluminosilicate particles is a key factor for a stable, reproducible impregnation and the maximal reinforcing efficiency of continuous fiber geopolymer composites.The work at hand focuses on the influence of the particle sizes of geopolymer precursors on the processing quality, microstructural development and final composite performance regarding the flexural, tensile and pullout behavior. Three differently sized fly ash (FA) sources were used to impregnate a carbon fiber heavy tow before curing at 75 °C. FA particles in the same size range as the filament diameter proved to be the most efficient, enhancing both mechanical properties of MCF and its bond to concrete matrix, well beyond the effects induced by other, coarser precursors. The results of the microscopic investigation, μCT, thermal gravimetric analyzes and mercury intrusion porosimetry measurements show that the use of this particle fraction resulted in the best fiber-matrix distribution over the cross-section, densest microstructure and highest fiber volume fraction in the impregnated yarn. Furthermore, the geopolymerization kinetics of all FAs at ambient temperature and at 75 °C were determined by isothermal calorimeter, showing an increase in the reaction rate with elevated curing temperature and higher particle finesse.

Effects of three biological combined with chemical methods on the microstructure, physicochemical properties and antioxidant activity of millet bran dietary fibre

The effects of cellulase hydrolysis separately combined with hydroxypropylation, carboxymethylation and phosphate crosslinking on the physicochemical properties and antioxidant activity of millet bran dietary fibre (MBDF) were investigated. Compared to cellulase hydrolysis alone, these dual modifications more effectively improved the soluble fibre content, water-swelling ability, viscosity, emulsifying capacity and cation-exchange capacity of MBDF but reduced the emulsion stability, brightness and polyphenol content of MBDF (P < 0.05). MBDF modified by cellulase hydrolysis combined with hydroxypropylation showed the highest emulsifying capacity (60.03 m2/g) and oil-adsorption capacity (3.32 g/g) but the lowest nitrite ion-adsorbing ability (NIAA). MBDF modified by cellulase hydrolysis with carboxymethylation showed the highest surface hydrophobicity, cation-exchange capacity (0.352 mmol/g) and NIAA (152.89 μg/g). MBDF modified by cellulase hydrolysis combined with phosphate crosslinking exhibited excellent copper ion-adsorbing ability (19.97 mg/g) and viscosity (19.33 cp). Moreover, these dual modifications all enhanced the Fe2+ chelating ability and reducing power of MBDF (P < 0.05).

Molecular dynamics simulation and finite element method investigation of PTFE/carbon fiber composite tribological properties

The mechanical parameters of polytetrafluoroethylene (PTFE), microstructures of carbon fiber (CF) and PTFE-CF interface were calculated based on the density function theory, molecular dynamics and finite element simulations. Then the friction models of GCr15-PTFE/CF composite were constructed, and the friction mechanisms of PTFE/CF composite were analyzed. The results show that the friction coefficients of composite materials containing different CF defect ratios are almost the same, indicating that the defect ratio has little influence on the friction coefficient. The position of CF in the PTFE matrix has a great impact on CF damage; the closer it is to the upper specimen during friction, the more serious the damage. In addition, the disordered structure was observed to have the most serious damage.

Improving the interlaminar bonding and thermal conductivity of polymer composites by using split-radial mesophase pitch-based carbon fiber as reinforcement

Mesophase-pitch-based carbon fiber (MPCF) reinforced polymer (MPCFRP) have excellent properties such as high thermal conductivity and high modulus, but the significant anisotropy and surface inertness of MPCF result in the poor interlaminar thermal conductivity and interface bonding of MPCFRP, which greatly limits its application. To address this issue, MPCF-A with split-radial structure was prepared through fiber structure modulation. Compared with the conventional skin-core fiber (MPCF-B), the higher surface roughness and chemical activity of MPCF-A contribute to stronger mechanical locking and chemical bonding between fibers and resin, meanwhile open wedge crack and better graphite microcrystalline structure of MPCF-A play a positive role in increasing the contact points and reducing the phonon scattering in the heat transfer. Therefore, the interlaminar shear strength (40.7 MPa) and interlaminar thermal conductivity (2.09 W/(m·K)) of MPCFRP-A are 9.12% and 27.4% higher than those of MPCFRP-B, respectively, on the basis of the excellent in-plane thermal conductivity (322.8 W/(m·K)). This study provides a reliable guide to improve the interlayer performance of MPCFRP by tailoring the fiber microstructure.

Damage characteristics of hybrid fiber reinforced concrete under the freeze-thaw cycles and compound-salt attack

This paper presents an experimental investigation on the damage characteristics and microstructures of hybrid fiber reinforced concrete (HFRC) subjected to the freeze-thaw（F-T）cycles and compound- salt attack. The effect of steel fiber content and steel-polypropylene fiber hybridization on the apparent morphology, mass loss, relative dynamic elastic modulus (RDEM), mechanical strengths in terms of compressive and flexural strengths were studied. The damage mechanism was explored based on an analysis of pore structures of specimens. The results showed that the F-T cycle has adverse effect on the physical and mechanical properties of specimens. The addition of fibers alleviates the damage degree of concrete, and the fiber hybridization shows more pronounced effect. Results from the porosity analysis indicate the pore sizes of 1.2HFRC are mainly distributed within 40 nm and those of OC are within 60 nm. The volume of larger pore size of 1.2HFRC increases less than the others after salt F-T cycles. Finally, based on Weibull distribution function, evolution equations for the salt-frozen damage of HFRC are developed by a combination of strength attenuation and RDEM degradation. The research results provide theoretical basis and reference for the practical application and building maintenance of fiber reinforced concrete.

Design of highly sensitive biosensors using hollow-core microstructured fibers for plasma sensing in aids with human metabolism.

Detection of low index liquid analytes in real-time, in-situ, and with high accuracy is of great importance in various scientific fields, particularly in medicine and biology. Accurate detection of plasma concentration in blood samples is one of the most significant usages of biosensors in medicine. In this paper, we report a highly sensitive biosensor using hollow core microstructure optical fibers (HC-MOFs) to detect low index liquid analytes with a particular focus on detection of plasma concentration in blood samples. We demonstrate how variations in plasma concentration in blood can change transmission spectra of the HC-MOF due to the photonic bandgap mechanism. We use the finite element approach to explore how the biosensor's performance depends on the number of capillary rings encircling the hollow core of the fibre. An average spectral and amplitude sensitivity of 8928.57nm/RIU and 1.21 dB/RIU is reported for the optimized design of HC-MOF for five capillary rings with a refractive index detection range of 1.333 to 1.3385 for different ratios of plasma in blood serum. The proposed biosensor can have potential application in liquid analyte detection in medicine, chemistry, and biology where real-time and accurate data about liquid analytes are necessary for human metabolism.

Influence of elevated temperature on the microhardness and microstructure of carbon fiber reinforced polymers

Carbon fiber-reinforced polymer (CFRP) has attracted attention for the reinforcement and retrofitting of concrete structures. Thus, their degradation in elevated temperatures is important feature to investigate. Herein, influence of elevated temperatures on microstructure and microhardness properties of different types of CFRP was investigated. A series of CFRP plate-, sheet-, and bar-type samples were fired at 150, 250, 350, and 450°C. Crystal structural properties of epoxy resin matrices and carbon fibers in the CFRP composites were examined using X-ray diffraction analysis. An increase in surface defects was observed for the fired CFRP plates and bars; however, there was no significant difference between the microstructures of the fired CFRP sheets. Hardness of CFRP plates fired at 150 and 250°C substantially decreased from 0.67 to 0.62 and 0.47 GPa, respectively, compared to that of unfired CFRP plate. Similarly, hardness of CFRP bars fired at 150, 250, and 350°C decreased from 2.09 to 1.73, 1.63, and 0.62 GPa, which is reduced by 17, 22, and 70%, respectively, compared to that of unfired CFRP bar. Decrease in hardness is attributed to several factors, such as mechanical degradation in the resin matrix, fiber/matrix debonding, and an increase in microcracks on the surface.

PRODUCTION AND PROPERTIES OF A PHOTOLUMINESCENT COATING BASED ON SEMICONDUCTOR QUANTUM DOTS IN A HOLLOW CORE OF MICROSTRUCTURED GLASS

Microstructured optical fibers (MOF) are a promising tool for improving biosensors, optical sensing, biomedical research, and clinical imaging. Approaches to the modification of the inner surface of microstructured optical fibers with a hollow core (MOF-HC) with polymer and photoluminescent materials using layer-by-layer deposition technology was developed. The method allows not only varying the thickness and charge of the layers, but also controllably introduce functional structures into the layers, in particular nanoparticles. The layer-by-layer deposition of polydiallyldimethylammonium chloride (PDDA) cationic polyelectrolyte with an average molecular weight (200 - 350 kDa) and negatively charged fluorescent nanoparticles - cadmium-free quantum dots (QD) of the AgInS2/ZnS structure, luminescent red (625 nm), orange (606 nm), yellow (570 nm) and green (556 nm) was investigated. QDs of the AgInS2/ZnS core/shell structure were obtained by the one-pot aqueous synthesis and selectively separated by successive deposition into fractions according to the size and color of the luminescence. This ensured the similarity of the properties of QDs with different luminescence colors. It was found that with an increase in the number of bilayers PDDA/QD from 1 to 5, the long-wave shift of the HC-MOF transmittance spectrum is: for layers based on red QD - 10 nm, orange QD - 11 nm, yellow 7 nm and green 8 nm relative to the spectrum of the original HC-MOF. When QD is included in the composition of the photoluminescent coating in the HC-MOF, a decrease in the wavelength of the maximum emission of QD is recorded, while the application of a subsequent layer of PDDA leads to its increase. For citation: Kochergin T.P., Ponomaryova T.S., Goryacheva I.Y. Production and properties of a photoluminescent coating based on semiconductor quantum dots in a hollow core of microstructured glass. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2023. V. 66. N 2. P. 85-91. DOI: 10.6060/ivkkt.20236602.6615.

Temperature Sensing Characteristics of Two Fundamental Solitons in a Glycerin-Filled Microstructured Optical Fiber

In this paper, the temperature sensing characteristics of two fundamental solitons in a glycerin-filled six-hole microstructured optical fiber (MOF) were systematically exploited through experiment and simulation. The six-hole MOF has a large duty cycle, which can increase the space to fill the temperature-sensitive material glycerin for improving the temperature sensing sensitivity. By detecting the center wavelength shift of 3dB bandwidth of two fundamental solitons at 1050 nm, 390 mW, a maximum sensitivity of -0.601 nm/ °C was obtained based on the first fundamental soliton and -0.598 nm/ °C was obtained based on the second. Simulation results combined with the experimental results showed that the higher the average pump power, the higher the temperature sensitivity, and the temperature sensitivity of the first was slightly higher than that of the second. The difference in sensing characteristics between the two fundamental solitons discovered in this study could provide a novel solution to solve the cross-sensitivity of dual-parameter sensing. To the best of our knowledge, this is the first research about utilizing two fundamental solitons for temperature sensing, which broadens the boundary of the nonlinear-based sensors, and has promising prospects in the fields of national defense security, disease monitoring, agriculture production, etc.

Evolution of extreme events in chaotic light-injected semiconductor lasers

&lt;sec&gt;Rare ultrahigh pulses, classified as rogue waves (RWs), are inevitable and catastrophic in many different systems. Considering the damage they may produce, it is meaningful to understand the formation mechanism of these pulses and, if possible, control them. However, the rarity of RW and the difficulty in implementing the experiment are major limitations to understanding their formation. In 2007, Solli et al. (Solli D R, Ropers C, Koonath P, Jalali B &lt;ext-link ext-link-type="uri" xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="https://www.nature.com/articles/nature06402"&gt;2007 &lt;i&gt;Nature&lt;/i&gt; &lt;b&gt;450&lt;/b&gt; 1054&lt;/ext-link&gt;) introduced the concept of optical RW, i.e. extreme event (EE) by comparing the appearance of oceanic RWs with the propagation of light fields in optical fibers. After that, the research of EEs entered into a flourishing period and different optical systems were proposed to analyze the generation and origin of EEs. Linear system is one of the most widely studied EE systems, such as linear light propagation in glass fibers, random media, and linear interference models. In addition to the linear systems mentioned above, efforts have also been made to produce nonlinear systems of EEs, such as microstructure fibers and tapered gradient exponential nonlinear fibers. In these nonlinear systems, the formation mechanism of EE is studied by using the nonlinear Schrödinger equation. Recently, the EEs in semiconductor laser systems have received a great deal of attention. On the one hand, semiconductor lasers with rich dynamic properties provide a cheap and controllable platform for understanding and predicting EE. The behavior of EE, on the other hand, is a powerful tool for understanding the fundamental mechanism of different laser systems.&lt;/sec&gt;&lt;sec&gt;In this work, based on the EEs generated in a semiconductor laser with phase-conjugate optical feedback (the master laser, ML), we inject its output into another free-running semiconductor laser (the slave laser, SL) and discuss the evolution of EEs in the system by numerical simulation. Herein, we analyze the influence of injection parameters on EEs through the two-dimensional maps of the relative number of EEs in the injection-parameter space. It can be concluded that in an area of high correlation, the relative number of EEs in SL tends to be a stationary value close to that in ML, while it may be enhanced in some weakly correlated regions. The results demonstrate the possibility of controlling EEs by optical injection, which is beneficial to optimizing the performance of chaotic laser systems or expanding their application scope.&lt;/sec&gt;

Effect of Heat Treatment on Composition, Microstructure and Mechanical Property of Domestic KD-SA SiC Fibers

Effect of Heat Treatment on Composition, Microstructure and Mechanical Property of Domestic KD-SA SiC Fibers

The correlation of sulfonation reaction kinetics with the degree of sulfonation (DS) and its effects on microstructure and morphology of electrospun fibers for the membrane of fuel cells.

Sulfonation is among the frequently used surface modification methods to endow new surface properties on polymer fibers. Direct sulfonation is the simplest chemical modification via incorporation of sulfonate functional groups onto fibers' surfaces at ordinary conditions. However, the process of functionalization compromises other properties of the electrospun membrane due to the extent of sulfonation reaction that occurred. This study was carried out to determine the effects on microstructure and morphology of crosslinked electrospun polybenzoxazine (PBz) fibers by correlating the reaction kinetics using a specific reaction parameter with the degree of sulfonation (DS). The kinetics of sulfonation reaction for PBz fibers is an electrophilic-based, first-type substitution mechanism where only one sulfonic acid (-SO3H) group is attached to each of the repeating units in the aromatic structure of PBz under ordinary conditions. From a previous study, the rate of change of ion exchange capacity (IEC) was derived as a logarithmic correlation that increased rapidly for some time and became constant. This study employed the derived empirical relationship based on reaction kinetics to correlate the degree of sulfonation (DS) with IEC at varying reaction time. DS was calculated as 55%, 66% and 77%, for 3, 6 and 24 h, respectively. The maximum IEC of 2.71 with the corresponding DS of 100% was obtained theoretically but since sulfonation reaction kinetics at ordinary conditions proceeds at slower phase, it can only attain 86% DS with maximum IEC of 2.44 at a calculated time of 48 h. Sulfonation was confirmed by the functional groups present in the structural composition of PBz fibers using ATR-FTIR which were quantified based on the absorbance in the IR spectra showing an increased peak height with increased reaction time for the first 6 h. Morphological analyses using SEM images revealed an increase in fiber diameter with increased sulfonation time. In addition, the higher reaction time showed the effects of longer acid exposure which compromised the fibers' structural integrity with the presence of broken fibers and defects on fibers' surfaces after 24 h. The electrospun PBz fibers sulfonated for 6 h achieved the highest IEC value with DS of 66% which was enough to attain the balance of degree of sulfonation with electrochemical and morphological properties.

Using Diffusion Tensor Imaging to Explore the Changes in the Microstructure of Canine Vocal Fold Scar Tissue

To apply diffusion tensor imaging (DTI) in measurement of the diffusion characteristics of water molecules in vocal fold scar tissue, combined with the analysis of textural characteristics of collagen fibers in the cover layer of the vocal folds to explore the feasibility of DTI in the qualitative and quantitative diagnosis of vocal fold scars and the evaluation of microstructural changes of vocal fold scar tissue. A unilateral injury was created using micro-cup forceps in the left vocal fold of six beagles. The contralateral normal vocal fold was used as a self-control. Five months postinjury, the larynges were excised and placed into a magnetic resonance imaging (MRI) system (9.4T BioSpec MRI, Bruker, German) for scanning and extraction of the diffusion parameters, fractional anisotropy (FA) and tensor trace in the anterior, middle, and posterior portions of the vocal fold cover layer. These parameters were then analyzed for statistical significance between the scarred vocal fold and the normal vocal fold. After MRI scanning, the tissue of the vocal folds was divided into anterior, middle, and posterior parts for sectioning and staining with hematoxylin and eosin, and samples were subsequently digitally scanned for texture analysis. The irregularity parameters, energy, contrast, correlation, and homogeneity, of collagen fibers of the vocal folds and the mean gray value of collagen fibers were calculated by the gray-level co-occurrence matrix (GLCM) texture analysis method. The differences in the mean value of the two sides of the vocal fold were compared. In addition, Pearson correlation analysis was performed between DTI parameters and irregularity parameters. The FA of the left vocal fold cover layer was significantly lower compared to the self-control group (P=0.0366), and the tensor trace value on the left vocal fold cover layer was significantly higher compared to the self-control group (P=0.0353). The FA was significantly higher in the anterior part of the right vocal fold cover layer compared to the middle and posterior parts of the same side (P=0.0352), and the tensor trace was significantly lower in the anterior part of the right vocal fold cover layer compared to the middle and posterior parts of the same side (P=0.0298). There were no significant differences in FA and tensor trace between the middle and posterior parts of the vocal fold cover layer. The mean gray value of the left vocal folds cover layer was significantly smaller than the right vocal fold cover layer (P=0.0219), the energy of the left vocal fold cover layer was significantly smaller than that of the right vocal fold cover layer (P < 0.0001), the contrast of the left vocal folds cover layer was significantly larger than that of the right vocal fold cover layer (P=0.0002), the correlation of the left vocal folds cover layer was significantly smaller than the right vocal fold cover layer (P=0.0002), and the homogeneity of the left vocal folds cover layer was significantly smaller than the right vocal fold cover layer (P=0.0003). Pearson correlation analysis yielded values of r=0.926, P=0.000 between the FA and mean gray value; r=-0.918, P=0.000 between FA and energy; r=-0.924, P=0.000 between the FA and homogeneity, r=-0.949, P=0.000 between tensor trace and mean gray value; r=0.893, P=0.000 between the tensor trace and energy; and r=0.929, P=0.000 between the tensor trace and homogeneity. FA and tensor trace can be used as effective parameters to reflect microstructural changes in vocal fold scars. DTI is an objective and quantitative method of analyzing vocal fold scarring, and it noninvasively evaluates the microstructure of vocal fold collagen fibers.

Inhibiting MicroRNA-141-3p Improves Musculoskeletal Health in Aged Mice.

Emerging evidence shows that the microRNA-141-3p is involved in various age-related pathologies. Previously, our group and others reported elevated levels of miR-141-3p in several tissues and organs with age. Here, we inhibited the expression of miR-141-3p using antagomir (Anti-miR-141-3p) in aged mice and explored its role in healthy aging. We analyzed serum (cytokine profiling), spleen (immune profiling), and overall musculoskeletal phenotype. We found decreased levels of pro-inflammatory cytokines (such as TNF-α, IL-1β, IFN-γ) in serum with Anti-miR-141-3p treatment. The flow-cytometry analysis on splenocytes revealed decreased M1 (pro-inflammatory) and increased M2 (anti-inflammatory) populations. We also found improved bone microstructure and muscle fiber size with Anti-miR-141-3p treatment. Molecular analysis revealed that miR-141-3p regulates the expression of AU-rich RNA-binding factor 1 (AUF1) and promotes senescence (p21, p16) and pro-inflammatory (TNF-α, IL-1β, IFN-γ) environment whereas inhibiting miR-141-3p prevents these effects. Furthermore, we demonstrated that the expression of FOXO-1 transcription factor was reduced with Anti-miR-141-3p and elevated with silencing of AUF1 (siRNA-AUF1), suggesting crosstalk between miR-141-3p and FOXO-1. Overall, our proof-of-concept study demonstrates that inhibiting miR-141-3p could be a potential strategy to improve immune, bone, and muscle health with age.

Comments about birefringence dispersion, with group and phase birefringence measurements in polarization-maintaining fibers

A recent JEOS-RP publication proposed Comments about Dispersion of Light Waves, and we present here complementary comments for birefringence dispersion in polarization-maintaining (PM) fibers, and for its measurement techniques based on channeled spectrum analysis. We start by a study of early seminal papers, and we propose additional explanations to get a simpler understanding of the subject. A geometrical construction is described to relate phase birefringence to group birefringence, and it is applied to the measurement of several kinds of PM fibers using stress-induced photo-elasticity, or shape birefringence. These measurements confirm clearly that the difference between group birefringence and phase birefringence is limited to 15–20% in stress-induced PM fibers (bow-tie, panda, or tiger-eye), but that it can get up to a 3-fold factor with an elliptical-core (E-core) fiber. There are also surprising results with solid-core micro-structured PM fibers, that are based on shape birefringence, as E-core fibers.

A Reliable Anti-Interference Temperature Sensor Based on a Four-Hole Microstructure Optical Fiber Mach–Zehnder Interferometer

In this paper, an in-line Mach-Zehnder interferometer (ILMZI)-based temperature sensor of a sandwich-like composite structure was proposed and experimentally demonstrated. Using simple cleaving and splicing operations, ILMZI was formed by compactly sandwiching a section of four-hole microstructure optical fiber (FHMF) of ultra-short length between two segments of multi-mode fibers and single-mode fibers in turn. Thanks to the large thermo-optic coefficient difference between the silica and air modes in FHMF, the sensor achieves a comparable sensitivity of 67.29 pm/°C over a wide dynamic range of 20.8-100.4 °C. Because the sensing area length is only a few hundred microns, the long-term stability and anti-interference of the sensor is greatly enhanced. In addition, the large airhole design confines the propagation mode in silica medium by total internal reflection, reducing the interaction between the liquid sample and the sensing element, making the sensor inert to the ambient refractive index. The maximum response deviation of the sensor under micro-vibration disturbances is 3.51×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> nm/°C, and the maximum cross-sensitivity under strain disturbances is only 0.0018 °C/με. The proposed sensor is excellent in performance, easy in fabrication, simple in structure and low in cost, which can be expected to be used in practical temperature sensing applications without any additional packaging.

Research on Bending Characteristics of Hollow-Core Micro-Structured Fibers for Development of Fiber Optic Gyroscopes

Research on Bending Characteristics of Hollow-Core Micro-Structured Fibers for Development of Fiber Optic Gyroscopes

High-Resolution Optical Fiber Salinity Sensor With Self-Referenced Parallel Fabry–Perot Fiber Microcavity

A high-resolution salinity sensor based on a self-referenced parallel Fabry–Perot fiber microcavity is proposed. The sensor is fabricated by inserting a short piece of exposed-core microstructure fiber (ECF) between multimode fiber (MMF) and single-mode fiber (SMF). Due to the unique exposed-core fiber structure and the specially designed SMF-MMF-ECF-SMF structure, two prominent parallel Fabry–Perot interferometers (FPIs) are constructed. Besides, a self-referenced differential phase-demodulation technology is proposed to eliminate the wavelength uncertainty of the spectra measurement devices. Enhanced demodulation system stability and accuracy are achieved by analyzing the phase shift responses of the reflection spectrum. A high salinity-phase sensitivity of 17.36 deg/ ‰ in the range from 0 ‰ to 35 ‰ is obtained, and the corresponding refractive index (RI) sensitivity is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${1.04} \times {10} ^{{5}}$ </tex-math></inline-formula> deg/RIU. The salinity resolution and RI resolution are as low as 0.0058 ‰ and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${9.6} \times {10} ^{-{7}}$ </tex-math></inline-formula> RIU, respectively, which gives a great potential for harsh environmental monitoring and label-free biochemical analysis.

Stress-Induced Yb-Doped Large-Mode-Area Polarization-Maintaining Microstructured Fibers with Deviation of the Single-Mode Transmission Band and Delocalization of Higher-Order Modes

Stress-Induced Yb-Doped Large-Mode-Area Polarization-Maintaining Microstructured Fibers with Deviation of the Single-Mode Transmission Band and Delocalization of Higher-Order Modes