Fiber Position Research Articles

DLW-printed optical fiber micro-connector kit for effective light coupling in optical prototyping

Microoptics opens up new opportunities for effective transformation of the radiation wavefront at the needed position using optical fiber. Here we discuss the use of a micro-connector kit for relative positioning of an optical fiber with nanometer accuracy. A single technological process of the DLW-lithography (Direct Laser Writing) to create all optical elements of the kit: optical fiber micro-connector and micro-lens, is used to solve the key problem of the precise alignment of optical elements. Micro-lens assisted single-mode fiber with high light coupling efficiency is demonstrated. Further improvement of this light coupling kit is based on aligned micro-lens array combined with multi-core optical fiber (MCF), where each micro-lens is located directly opposite to its own core. Nanometer accuracy of micro-lenses location could be achieved due to proposed and demonstrated printing process. Such kit significantly improves performance of optical instruments for spatially resolved spectroscopy. One of the possible important applications of MCF-based light coupling kit with individual lens design for each core is a real-time 3D-imaging. Moreover, parallel multi-beam laser processing with such kit is of great importance.

Mesoscale characterization of continuous fiber reinforced composites through machine learning: Fiber chirality

A method of quantifying fiber chirality, the twist of continuous fibers through a volume, is defined and applied to both phantom data and real data. Specifically, a field quantity termed the fiber chirality based on the anti-symmetric part of the gradient of the fiber orientation is introduced. For this method of estimation, the input is the set of fiber positions gathered from the stack of images which represent the sample volumes. The phantom sample is generated and several different real continuous fiber reinforced matrix composites are experimentally characterized. Each phantom dataset contains a bundle of fibers that rotate about a center axis with a user-defined angle at each step in the z-direction. The chirality of the fibers is calculated based on the pre-characterized positions using a machine learning algorithm. To validate the method of quantification, our chirality estimation method results in a colormap with an angle of rotation that becomes increasingly more similar to the user-defined angle with decreasing inter-slice distance. Fiber positions from real data are then input into the estimation method and the results are compared.

The southern stellar stream spectroscopic survey (S5): Overview, target selection, data reduction, validation, and early science

ABSTRACT We introduce the southern stellar stream spectroscopy survey (S5), an on-going program to map the kinematics and chemistry of stellar streams in the southern hemisphere. The initial focus of S5 has been spectroscopic observations of recently identified streams within the footprint of the dark energy survey (DES), with the eventual goal of surveying streams across the entire southern sky. Stellar streams are composed of material that has been tidally striped from dwarf galaxies and globular clusters and hence are excellent dynamical probes of the gravitational potential of the Milky Way, as well as providing a detailed snapshot of its accretion history. Observing with the 3.9 m Anglo-Australian Telescope’s 2-degree-Field fibre positioner and AAOmega spectrograph, and combining the precise photometry of DES DR1 with the superb proper motions from Gaia DR2, allows us to conduct an efficient spectroscopic survey to map these stellar streams. So far S5 has mapped nine DES streams and three streams outside of DES; the former are the first spectroscopic observations of these recently discovered streams. In addition to the stream survey, we use spare fibres to undertake a Milky Way halo survey and a low-redshift galaxy survey. This paper presents an overview of the S5 program, describing the scientific motivation for the survey, target selection, observation strategy, data reduction, and survey validation. Finally, we describe early science results on stellar streams and Milky Way halo stars drawn from the survey. Updates on S5, including future public data releases, can be found at http://s5collab.github.io.

Flexural and energy absorption properties of natural-fiber reinforced composites with a novel fabrication technique

Abstract In this paper, two types of natural fibers (jute fiber and cotton fiber) were arranged in different cross-section positions on natural fiber-reinforced epoxy composites (NFR-EC) by using a novel hole arrangement–threading–glue filling method. A three-point bending experiment was carried out to reveal the flexural response, failure types, and energy absorption properties of NFR-EC. An analytical model was applied to analyze the force distribution of natural fibers and epoxy in NFR-EC. Results showed that the hole arrangement–threading–glue filling method successfully manufactured an NFR-EC, which can adjust the volume fraction and cross-section position of natural fibers and the cross-sectional shape of NFR-EC. The addition of fibers below the neutral axis of the cross-section significantly improved the flexural properties and energy absorption capacity of NFR-EC.

The hydrodynamic lift of a slender, neutrally buoyant fibre in a wall-bounded shear flow at small Reynolds number

The hydrodynamic lift velocity of a neutrally buoyant fibre in a simple shear flow near a wall is determined for small, but non-zero, fibre Reynolds number, illustrating the role of non-sphericity in lift. The rotational motion and effects of fibre orientation on lift are treated for fibre positions that induce and do not induce solid-body wall contacts. When the fibre does not contact the wall its lift velocity can be obtained in terms of the Stokes flow field by using a generalized reciprocal theorem. The Stokes velocity field is determined using slender-body theory with the no-slip velocity at the wall enforced using the method of images. To leading order the lift velocity at distances large compared with the fibre length and small compared with the Oseen length is found to be $0.0303\unicode[STIX]{x1D70C}\dot{\unicode[STIX]{x1D6FE}}^{2}l^{2}a/(\unicode[STIX]{x1D707}\ln [2l/a])$, where $l$ and $a$ are the fibre half-length and radius, $\unicode[STIX]{x1D70C}$ is the density, $\dot{\unicode[STIX]{x1D6FE}}$ is the shear rate and $\unicode[STIX]{x1D707}$ is the viscosity of the fluid. When the fibre is close enough to the wall to make solid-body contact during its rotational motion, a process known as pole vaulting coupled with inertially induced changes of fibre orientation determines the lift velocity. The order of magnitude of the lift in this case is larger by a factor of $l/a$ than when the fibre does not contact the wall and it reaches a maximum of $0.013\unicode[STIX]{x1D70C}\dot{\unicode[STIX]{x1D6FE}}^{2}l^{3}/(\unicode[STIX]{x1D707}\ln [l/a])$ for the case of a highly frictional contact and about half that value for a frictionless contact. These results are used to illustrate how particle shape can contribute to separation methods such as those in microfluidic channels or cross-flow filtration processes.

Exploiting the aiming beam to increase the safety of laser lithotripsy: Experimental evaluation of light reflection and fluorescence.

In Holmium laser lithotripsy, usually, the surgeon is guided by a visible beam superimposing the infrared (IR) treatment radiation. It has been shown that a green aiming beam excites stone autofluorescence. This fluorescence signal can be used for calculi detection to check the correct fiber position before triggering the IR laser, thus preventing damage to soft tissue and application devices. However, also the directly reflected green light from the fiber tip gives valuable information on fiber position and its surface condition. An external fiber-fiber-coupling-box (fiber core diameter 365 µm) for pulsed holmium laser radiation (2.1 µm) was set up containing a green diode laser module (520 nm, average power on the sample <0.5 mW) and optics and detectors for measuring the reflected light of this aiming beam as well as the fluorescence excited with it. Measurements were done via a lock-in technique with more than 20 human calculi samples and porcine calix in vitro. After the implementation of automatic data storage signals during ongoing in vitro lithotripsy procedures were recorded with the fiber positioned on tissue, stone, or in/on medical equipment (working channel of an endoscope, stone retrieval basket). Stone fluorescence signals measured were a factor of 7 to >100 higher than those of tissue. Stone fluorescence was detectable in "non-contact mode" with a linear signal decrease over a distance up to ~1 mm in front of the fiber tip (core diameter 365 µm) and with severely damaged fibers (max. decrease: 75% with pinched off fiber). Reflection signals of the fiber tip surface in air and water surrounding decreased significantly when the fiber was damaged; measured ratios of intact to damaged fiber found in the air were (5-17):1 and in water (1.6-3.7):1. Surfaces in front of the fiber aggravated the evaluation of fiber condition due to reflections but enabled to detect, for example, the working channel of a flexible endoscope in combination with the (missing) fluorescence signal. Autofluorescence induced by a green aiming beam can be exploited for stone detection in laser lithotripsy. A reflection measurement can give further information on fiber condition and position. Implementing this kind of safety features for an automatic block of IR laser emission in case of weak or missing fluorescence and un-normal reflections can assist the surgeon by avoiding tissue perforation, and damage to medical devices such as endoscopes. Lasers Surg. Med. © 2019 Wiley Periodicals, Inc.

Effect of fiber binding force on the molding of Cf/Al composites

The dispersibility of non-damaged carbon fibers and the stability of fiber position have a crucial influence on the properties of continuous carbon fiber reinforced aluminum matrix (Cf/Al) composites. In order to avoid the damage to the fiber caused by excessive infiltration pressure, which can be controlled by adjusting the distance from the vibration head to the fiber bundle. The effect of different binding force on the distribution and the fixed position of non-damaged carbon fibers in the matrix were studied. The results show that with the fiber binding force increases (0 N, 2 N and 4 N), the carbon fiber bundles can be stably located in a predetermined position and gradually completely infiltrated, but with the binding force further increases (6 N and 8 N), the fiber clusters and uninfiltrated defects appeared again. It is found that the proper fiber binding force can ensure that the carbon fiber does not shift under the infiltration pressure, so that the fibers distribute uniformly in the composite, but the excessive binding forces can obviously inhibit the dispersion of the fibers. Tensile test results show that the ultimate tensile strength increases first and then decreases with the increasing of fiber binding force. When binding force reach to 4 N, the tensile performance of the composites is 203 MPa at its best. The uniform distribution of carbon fibers in the matrix play an important role in improving the tensile performance of Cf/Al composites.

Axial and Radial Variation of Fibre Characteristics of Bambusa vulgaris

This study was carried out to investigate the axial and radial variations of fibre characteristics of Bambusa vulgaris. There were eighteen treatments for both axial and radial variations. The treatments were replicated three (3) times, in Complete Randomized Design (CRD). The experiment was carried out at the Wood Anatomy Laboratory of the Department of Forest Product Development and Utilization, Forestry Research Institute of Nigeria, Ibadan. Three samples (3) stands of B. vulgaris were randomly selected. Samples collected were cut into 10cm discs at 25%, 50% and 75% of the total height (axial positioning). The samples discs were partitioned into two zones which are core and peripheral (bark) layers. From each of the disc, 3 slivers were obtained both from radial and axial positions. Slivers obtained were macerated with an equal volume (1:1) of 10% glacial Acetic acid and 30% Hydrogen Peroxide (H2O2) at 100 ±2°C. The resulting image on light microscope screen was measured for fibre length, fibre diameter and lumen width.&#x0D; At 50% sampling height and at outer layer, the highest fibre length of 3.25 mm, followed by 3.06 mm of bamboo sample stand 3 while the least 2.28 mm was recorded in sample stands 2 of 75% axial positioning and at peripheral layer. The lumen width ranged between 3.52 × 10-3 μm to 4.46 × 10-3 μm in the radial direction from the core to the peripheral (bark) of the bamboo. The result obtained for mean values of fiber diameter along the bamboo height ranged from 3.53 × 10-3 µm to 4.46 × 10-3 µm across the three (3) bamboo stands, sampling height and radial direction sampling respectively.&#x0D; Among the fibre positioning, the fibre collected from 50% of the sampling height have higher fibre diameter, lumen width and fibre diameter at the peripheral region compare to the others.

Focal Ratio Degradation for Fiber Positioner Operation in Astronomical Spectrographs

Focal ratio degradation (FRD), the decrease of light’s focal ratio between the input into an optical fiber and the output, is important to characterize for astronomical spectrographs due to its effects on throughput and the point spread function. However, while FRD is a function of many fiber properties such as stresses, microbending, and surface imperfections, angular misalignments between the incoming light and the face of the fiber also affect the light profile and complicate this measurement. A compact experimental setup and a model separating FRD from angular misalignment was applied to a fiber subjected to varying stresses or angular misalignments to determine the magnitude of these effects. The FRD was then determined for a fiber in a fiber positioner that will be used in the Subaru Prime Focus Spectrograph (PFS). The analysis we carried out for the PFS positioner suggests that effects of angular misalignment dominate and no significant FRD increase due to stress should occur.

A Study on The Effect of Sic on Mechanical Properties of Carbon/Banana Peduncle Fiber Reinforced Epoxy Composites

Nowadays the position of natural fibers in the world fiber is stable, growing in the area of their application, not only in textiles but also in more eco-friendly composites. This work is focused on study of the effect of SiC as filler material on the banana peduncle/Carbon fibers reinforced hybrid composites. Four different laminates are fabricated by varying the matrix composition (BP, BP+SiC, carbon+BP, Carbon+BP+SiC ). The alkaline treatment with 6% NaoH of the BP fibers improves the specific strength and binding properties. The filler added composites laminates shows higher mechanical properties. From the results, it is seen that mechanical properties like Tensile, Flexural, ILSS, Impact and hardness are improved by 89, 75, 99, 68 and 64% by the addition of the SiC to the banana peduncle/Carbon fiber composite laminate.

Sema3a-Nrp1 Signaling Mediates Fast-Twitch Myofiber Specificity of Tw2+ Cells.

We previously identified a unique population of interstitial muscle progenitors, marked by expression of the Twist2 transcription factor, which fuses specifically to type IIb/x fast-twitch myofibers. Tw2+ progenitors are distinct from satellite cells, a muscle progenitor that expresses Pax7 and contributes to all myofiber types. Through RNA sequencing and immunofluorescence, we identify the membrane receptor, Nrp1, as a marker of Tw2+ cells but not Pax7+ cells. We also found that Sema3a, a chemorepellent ligand for Nrp1, is expressed by type I and IIa myofibers but not IIb myofibers. Using stripe migration assays, chimeric cell-cell fusion assays, and a Sema3a transgenic mouse model, we identify Sema3a-Nrp1 signaling as a major mechanism for Tw2+ cell fiber-type specificity. Our findings reveal an extracellular signaling mechanism whereby a cell-surface receptor for a chemorepellent confers specificity of intercellular fusion of a specific muscle progenitor with its target tissue.

Fiber-reinforced polymer plates for strengthening web opening in steel I-beams under cyclic loading

This article is interested in finding the most appropriate strengthening scheme for web opening in steel I-beam under cyclic loading. Different opening shapes and locations were strengthened using two different fiber-reinforced polymer plates: carbon fiber–reinforced polymer and basalt fiber–reinforced polymer. A three-dimensional nonlinear finite element model was adopted using ANSYS program. The results showed that the high strength of carbon fiber–reinforced polymer plates helped the steel beam to recover its original strength; however, noticeable reduction was observed in beam ductility and in the number of inelastic excursions that took place before failure. Moreover, remarkable difference in stress concentration existed at the position of the carbon fiber–reinforced polymer plate edges. Under cyclic loading, fiber-reinforced polymer composites with low modulus of elasticity such as basalt fiber–reinforced polymer managed to eliminate these deficiencies using longer strengthening length. The most appropriate strengthening length and scheme for each opening case were outlined.

Leaf structure in Amorimia and closely related Neotropical genera and implications for their systematics and leaf evolution in Malpighiaceae

AbstractAmorimia (Malpighiaceae) was recently segregated from the polyphyletic Mascagnia and placed in the malpighioid clade; identifying new characters based on leaf structure is among the first steps towards a proper generic delimitation of these segregates of Mascagnia. A comprehensive study describing and testing the relevance of leaf-structure characters in the evolution of Amorimia and related Neotropical genera is presented. We sampled all 15 Amorimia spp. and, as outgroups, eight species from the closely related Neotropical genera (Diplopterys, Ectopopterys, Mascagnia, Peixotoa and Stigmaphyllon). We scored 85 structural characters and mapped them on the most recent phylogenetic tree recovered for the genera. The presence of druses in the palisade parenchyma, the position of fibres alongside the vascular bundle and the occurrence of fibre blocks near the margin of the leaf blade were recovered as anatomical synapomorphies for Amorimia. Our results are a first step towards recovering anatomical and macromorphological synapomorphies for newly identified lineages of Malpighiaceae, such as Amorimia.

Fiber Positioner Based on Flexible Hinges Amplification Mechanism

Due to the nonlinear effect and the thermal effect, a single optical fiber has limitations in the output power. A beam combination of laser arrays based on adaptive optics can both improve the output power and ensure higher beam quality. This article puts forward one novel fiber positioner structure based on the flexible hinges amplification mechanism, which is the adaptive fiber optics collimator (AFOC), to correct tip-tilt aberration. The theoretical model was established, and the amplification ratios between the output displacement and device’s structure parameters were calculated. The first 6 orders of the mode shape of the vibration of amplification mechanism was obtained by using a modal analysis. Analysis results revealed an excellent performance for the flexible hinges amplification mechanism. The novel fiber positioner has good prospects for applications in laser beam combination systems for ideal tip-tilt control.

Esophageal mucosal innervation in functional heartburn: Closer to healthy asymptomatic subjects than to non-erosive reflux disease patients.

Mucosal innervation in non-erosive reflux disease (NERD; pathological esophageal acid exposure, normal macroscopic mucosa) is clearly distinct from that of healthy volunteers (HV) and from patients with esophagitis or Barrett's esophagus: The nerves in NERD are situated much closer to the luminal surface of the mucosa. Patients with functional heartburn (FH) have a similar symptom profile to patients with NERD and indistinguishable macroscopic appearances. However, they have physiological acid exposure and no reflux-symptom association. The aim of our study was to delineate the position of esophageal mucosal nerve fibers in patients with FH and compare it with that in NERD and HV. Distal esophageal biopsies from patients with FH were immunohistochemically stained for CGRP. CGRP-positive nerve fibers were identified, and their position relative to the lumen was determined. These results were compared to our previously published cohort of HV and NERD. Eleven patients were included in the FH group with a mean age of 46years (range 33-69); 7F:4M. Nine patients had visible nerve fibers. The location of the afferent nerve fibers in the distal esophageal mucosa (median of 22, range 10.4-28) was similar to the HV group (median 25.5) and significantly deeper than the superficial nerves seen in NERD (median 9.5). The mucosal innervation pattern in FH is more alike that of healthy individuals than that of NERD, with afferent nerves lying deep in the mucosa, away from the luminal surface. This supports the theory that heartburn in FH has a distinct nociceptive pathophysiology.

An experimental preparation of fibre concrete to software’s detection of fibres

Fibre concrete requirements are only met if the fibres in its volume are evenly distributed. Their direction and orientation should be equal around each axis in a three-dimensional space. The requirement is that the fibres to be evaluated in the final hardened fibre concrete are cut from fibre concrete sections. Homogeneity can also be verified on fibre-concrete cross-sections. Fibre Position Evaluation is a mathematical task that is not presented here but is currently made up of the results of this experiment. In the first step, it was necessary to prepare samples to obtain the necessary cross-sections. In the next step, it was necessary to create conditions by creating a contrast between the fibres and the concrete to create software capable of detecting fibres. In this paper, the principle of detection of fibres based on the detection of cut section images is described. There are several methods used to highlight the concrete matrix over the fibres. Also presented are the results of adding and detecting fibres.

The DESI Fiber View Camera System

The Dark Energy Spectroscopic Instrument (DESI) is a 5000 fiber multi-object spectrometer now being installed at the prime focus of the 4 m Mayall telescope at Kitt Peak. Using DESI to measure ∼35 million galaxy redshifts and using the Baryon Acoustic Oscillation (BAO) technique to measure distances, the results will probe the nature of the recently discovered mysterious component of our universe called dark energy. Computer controlled robotic positioners move the 120 μm diameter fibers to positions of galaxies whose location on the sky have been obtained in a previous target selection imaging survey. To achieve good throughput the fibers should be centered on the target position to within 3 μm. The robotic positioners however are only capable of a 50 μm precision on their first move. To achieve the desired precision, the Fiber View Camera (FVC) system has been implemented. The FVC, located near the hole in the primary mirror of the Mayall telescope, has been designed to take an exposure of the focal plane, located at the prime focus some 12 m above the FVC, after the robotic positioners have completed their first move. The FVC is intended to measure the fiber locations with a precision of 3 μm and issue a set of fiber coordinate corrections for the second move correcting the fiber positions by the robotic positioners. Tests show that after two iterations better than 99% of the fibers will be in their intended location to within the desired precision. This paper describes the design of the FVC system, the R&D program preceding the final design, and the tests that have been carried out to demonstrate that the FVC can achieve the required precision.

Effect of Atmospheric Pressure Plasma Treatment of Glass Fibers on the Composite Strength of Endless Fiber-Reinforced Injection Molded Components

Injection molding is an efficient manufacturing process for short-fiber reinforced plastic components and is used for the production of semi-structural or geometrically complex components. To improve stiffness and strength, continuous fibers can be locally integrated inside the part during manufacturing. A local integration of fibers is not feasible for high output manufacturing processes but can be achieved by direct impregnation of endless fibers in the injection molding process. It is a challenging option to integrate endless fibers in injection molded parts in means of fiber position and infiltration. Thereby, the knowledge of the flow process of the injected melt must be precisely understood in means of orientation of the fibers to achieve a correct position. In previous works the process parameters for the impregnation of fibers and the composite behavior of untreated fibers were investigated. As a result, the surface pretreatment of the fibers can have an important effect on the composite and the direct impregnation of fibers. An important focus of this work is the pretreatment of glass fibers by plasma. The influence of the plasma parameters resulting on the adhesion properties between fiber and matrix and thus the bond strength of the composite are evaluated and measures for further adhesive property improvement are shown.

Pengesanan Isyarat Serak-Balik untuk Pengimbas Gentian Optik Resonans

We report the development of optical fibre resonant scanner that was developed using two multi-mode optical fibres that are attached side-by-side, producing a cantilevered optical fibre scanner. The optical fibre is mounted on photodiode and a small piezoelectric disk using polymer. The piezoelectric disk is driven with a sinusoidal signal that will then vibrate the mounted optical fibre, producing a single axis scan line. This paper reports on experimental detection of the back-scattered signal through dual-numerical aperture conFigureuration and identification of fibre position from a single scan line with respect to the optical reflections from the apertured reflector. The apertured reflector used was a brass metal with 1 mm of diameter that is placed before the imaging lens as a mechanism to differentiate the position of scan line. The single scan was obtained at its maximum length of 4.8mm with resonant frequency of 2.033kHz. The back-scattered signal from a target object is coupled back into the cladding of the optical fibre. The cladding mode is then stripped and detected by photodiode. The back scattered signal from the aperture is used to differentiate the position of fibre between the aperture and the target object itself. Differences in the position of the slots resulted pulses with different height and width, allowing the two backscattered signals to be distinguished. The experimental result is verified and compared with the theory back-scattered signal produced by such scanner.

Low polarization-dependent-loss double-layer grating coupler for three-dimensional photonic integration

Dense integration of silicon photonic devices is the key enabling technology for next-generation high-performance computers. In this paper, we propose a double-layer grating coupler for the future multi-layer photonic integrated system. With a pair of one-dimensional (1-D) gratings orthogonally vertical-stacked, the device can couple light between single-mode fiber and two separate waveguide layers, realizing polarization splitting and rotation in different layers simultaneously. Benefiting from the perfectly vertical coupling scheme and optimal fiber position (OFP) overlapping design, the coupling efficiency peak of the upper and lower grating are calculated to be 28% and 25% respectively. Assisted with a DBR bottom mirror, the coupling efficiency of the two gratings can be further enhanced to 33.2% and 28.9% respectively. For real application, the misalignment tolerance on grating overlapping and the incidence angle are carefully investigated. To achieve power balance between the two grating layers, the impact of top cladding thickness is analyzed and an optimized thickness of 0.6μm is chosen. From the simulation result of a back-to-back DLGC circuit, the coupling performance shows considerable robustness to the input polarization state and the PDL is under 0.5 dB within the wavelength range from 1536 nm to 1558 nm. Such a device can be a very promising solution to achieve polarization-independent coupling in the future three-dimensional (3-D) high density photonic integrated circuits.