Specialty Fibers Research Articles

Specialty Fiber and Related Technology for Fiber-Optic Sensing

Specialty Fiber and Related Technology for Fiber-Optic Sensing

Designing Optical Fibers: Fitting the Derivatives of a Nonlinear Pde-Eigenvalue Problem

When trying to fit data to functions of the eigensystem of a pde-eigenvalue problem, such as Maxwell’s equation, numerical differentiation is ineffective and analytic gradients must be supplied. In our motivating example of trying to determine the chemical composition of the layers of specialty optical fibers, the function involved fitting the higher order derivatives with respect to frequency of the positive eigenvalues. The computation of the gradient was the most time consuming part of the minimization problem. It was realized that if one interchanged the order of differentiation, and differentiated first with respect to the design parameters, fewer derivatives of the eigenvectors would be required and one could take full advantage that each grid point was affected by only a few variables. As the model was expanded to cover a fiber wrapped around a spool, the bandwidth of the linearized symmetric eigenvalue problem increased. At the heart of each of the iterative methods used to find the few positive eigenvalues was a symmetric, banded, indefinite matrix. Here we present an algorithm for this problem which reduces a symmetric banded matrix to a block diagonal matrix of 1 x 1 and 2 x 2 blocks. Fillin outside the band because of pivoting for stability is prevented by a sequence of planar transformations. Computationally the algorithm is compared to the block unsymmetric banded solver and the block positive definite symmetric band solver in LAPACK.

Radiation Tolerant Optical Fibers: From Sample Testing to Large Series Production

The process of selecting, manufacturing, and installing a large quantity (2500 km) of commercially available radiation tolerant specialty fibers is described. Radiation tests of various types of fibers from different manufacturers provided sufficient understanding of the radiation effects to select the best performing fiber type. Systematic verification of a sample of each preform assured a constant quality of the series production and allowed assessing the impact of small variations in the manufacturing process on the radiation hardness and the optical transmission characteristics. The fiber cable installation technique based on microjetting and plastic cable ducts has been validated for areas with high levels of radiation.

Interferometric Technique to Characterize Optical Fibres and Interrogate Guided-Wave-Based Micro-Resonator-Sensors

Abstract In the frame of development of new reference techniques, LNE has developed a Phase sensitive-Optical Low Coherence Reflectometer dedicated to the characterization of optical fibres less than one meter long and to the interrogation of guided-wave-based biosensors. Thus this technique is within the fields of optical telecommunication and biological applications. In this context: standard fibres, Bragg gratings, specialty fibres such as photonic crystal fibres and sensors made of micro-resonators have been studied. This tool has proven to be very performing as it gives relevant parameters with low uncertainty on components not accessible with other techniques or needed several different techniques. The setup is presented as well as the results of particular interest obtained on optical waveguides in the telecommunication and biological domains.

Design of multiplexed fiber optic chemical sensing system using clad-removable optical fibers

To prevent possible threats to public safety and economic loss from chemical leakage accidents, novel chemical sensing techniques for regular monitoring and leakage detection have been developed for various fields. We propose a fiber optic liquid chemical sensor (FOCS) system using specialty optical fibers and an optical time domain reflectometer (OTDR), and is based on the leaky wave mode sensing principle. OTDR enables simple multiplexing where individual sensor nodes along the fiber length could be interrogated by a common OTDR. The sensor node in the optical fiber is prepared by removing the desired length of a protective layer using mechanical stripping and chemical etching techniques. A novel laser stripping technique with superior capability to fabricate quasi-distributed dense sensor nodes is devised as well. The FOCS system is further analyzed to characterize the sensor response behavior in relation to the sensor node length and possible environmental and chemical temperature effect. Under the condition satisfying the leaky wave mode principle and within the minimum acceptable refractive index (RI) range by the system, this FOCS system could monitor numerous liquid chemicals with variable refractive indices and has been tested with positive results. In addition, the system shows the possibility for multi-point detection and is further expanded into a hybrid technique capable of estimating the refractive index range of the detected chemical.

Continuous-wave broadband generation using specialty fibers in fiber laser cavity

The broadband generated by the inclusion of dispersion shifted fiber, highly nonlinear fiber, and their combinations in the cavity of a filterless erbium-doped fiber ring laser is experimentally studied in this work. The gain spectrum of erbium-doped fiber and the nonlinear effects due to low-dispersion specialty fibers govern the spectral broadening. The experimental results are compared and analyzed with the aid of the dependence of the spectrum on the input pump power provided to the gain medium.

Characteristics of stand-alone microlenses in fiber-based fluorescence imaging applications

Microlens-ended fibers, which have found tremendous interest in the recent past, find potential biomedical applications, in particular, in endoscopic imaging. The work presented in this paper focuses on the stand-alone microlenses along with custom-fabricated specialty optical fiber, such as imaging fiber, for probe imaging applications. Stand-alone self-aligned microlenses have been fabricated employing microcompression molding and then attached at the end facet of imaging fiber. A detailed characterization of the fabricated microlens is carried and it demonstrates appropriate focusing ability, high fluorescence collection efficiency and imaging ability for biomedical applications. The surface roughness of the microlens is found to be 25 nm with a minimum spot size of 38 μm. The probe imaging system is found to be able to image the fluorescence microspheres of 10 μm size. The collection efficiency of the fiber probe with lens found to be enhanced by three times approximately.

Micro-Raman investigation of X or γ irradiated Ge doped fibers

Micro-Raman spectra have been recorded on Ge doped optical fibers before and after 10 keV-X or γ-ray irradiation up to doses of 1 MGy (X-ray) or 7.8 MGy (γ-ray). Our data provide evidence that, at such dose levels, the glass matrix is not modified in a detectable way. We observed that varying the Ge doping levels from 0 to about 11 wt.%, X or γ radiation sensitivity of the overall matrix remains unchanged. Such results are observed for fibers obtained with drawing conditions within the usual range used for the fabrication of specialty fibers as radiation-tolerant waveguides. Our data support the potentiality of fiber-based sensors using glass properties, e.g. Raman scattering, for applications in harsh environments as those encountered in nuclear power plants.

基于有源对准技术熔接双包层特种光纤

The fusion splicing of double-clad (DC) specialty fibers based on active alignment is crucial to the investigation of high-power monolithic fiber lasers. Given the wave-guiding characteristic of DC fiber, a light stripper is introduced in an active alignment experiment. We propose a novel method for stripping light that is convenient, highly efficient, and low cost. This method is also effective for low-numerical-aperture beams that escape from the fiber core. A splice loss as low as 0.05 dB is achieved.

Observing cross-sectional images of various optical fibers using low coherence transformed laser light

When the laser light of high optical coherence is launched into various optical fibers, such as a single-mode fiber, a multimode fiber, and a polarization-maintaining fiber, the observed optical patterns exhibit fragmented speckles due to the field interference of higher-order modes. Hence, the coherent laser light imaging system cannot be exploited to observe high-quality fiber crosssectional images. By putting a rotating diffuser directly on the laser beam, the original coherent speckled light spots at the fiber output endfaces could be smeared out efficiently and easily. Using the low coherence transformed laser light, we can thus obtain uniform fiber cross-sectional images and clear information for the tiny index structures in the specialty optical fibers.

基于强度检测的包层模谐振特种光纤传感系统

基于强度检测的包层模谐振特种光纤传感系统

Fusion splicing of double-clad specialty fiber using active alignment technology

Fusion splicing of double-clad specialty fiber using active alignment technology

Specialty Fiber Coupler: Fabrications and Applications

We review the research on specialty fiber couplers with emphasis placed on the characteristics that make them attractive for biomedical imaging, optical communications, and sensing applications. The fabrication of fiber couplers has been carried out with, in addition to conventional single mode fiber, various specialty fibers such as photonic crystal fiber, double clad fiber, and hole-assisted fiber with a Ge-doped core. For the fiber coupler fabrication, the side polishing and the fused biconical tapered methods have been developed. These specialty fiber couplers have been applied to optical coherence tomography, fluorescence spectroscopy, fiber sensors, and optical communication systems. This review aims to provide a detailed statement on the recent progress and novel applications of specialty fiber couplers.

X-ray irradiation effects on a multistep Ge-doped silica fiber produced using different drawing conditions

We report an experimental study based on confocal microscopy luminescence (CML) and electron paramagnetic resonance (EPR) measurements to investigate the effects of the X-ray (from 50 krad to 200 Mrad) on three specific multistep Ge doped fibers obtained from the same preform by changing some of the drawing conditions (tension and speed). CML data show that, both before and after the irradiation, Germanium Lone Pair Center (GLPC) concentrations are similarly distributed along the diameters of the three fibers and they are partially reduced by irradiation. The irradiation induces also the Non Bridging Oxygen Hole Center (NBOHC) investigated by CML and other paramagnetic defects as the Ge(1), Ge(2), E'Ge and E'Si investigated by EPR. We do not observe significant differences in the induced concentrations of these types of defects in the three fibers. All the results suggest that within the range of investigated drawing parameters (usual range for specialty optical fibers), the fiber radiation sensitivity is unaffected by these variations. Consequently, these results show that the drawing parameters (drawing tension and speed) cannot easily be adjusted to improve the radiation hardness of germanosilicate optical fibers.

Investigation of cladding and coating stripping methods for specialty optical fibers

Fiber optic sensing technology is used extensively in several engineering fields, including smart structures, health and usage monitoring, non-destructive testing, minimum invasive sensing, safety monitoring, and other advanced measurement fields. A general optical fiber consists of a core, cladding, and coating layers. Many sensing principles require that the cladding or coating layer should be removed or modified. In addition, since different sensing systems are needed for different types of optical fibers, it is very important to find and sort out the suitable cladding or coating removal method for a particular fiber. This study focuses on finding the cladding and coating stripping methods for four recent specialty optical fibers, namely: hard polymer-clad fiber, graded-index plastic optical fiber, copper/carbon-coated optical fiber, and aluminum-coated optical fiber. Several methods, including novel laser stripping and conventional chemical and mechanical stripping, were tried to determine the most suitable and efficient technique. Microscopic investigation of the fiber surfaces was used to visually evaluate the mechanical reliability. Optical time domain reflectometric signals of the successful removal cases were investigated to further examine the optical reliability. Based on our results, we describe and summarize the successful and unsuccessful methods.

Outstanding traits and thermal behaviour for the identification of speciality animal fibres

The extra-fine, soft and warm fibres used by the textile industry for manufacturing high-quality, luxury textiles are obtained from the undercoat hair of several domestic mammals of the genera Capra, Bos, Camelus, and Lama. The demand for ‘speciality fibres’ by the fashion world represents an important opportunity for livelihoods, on condition that conservation of the wild species is preserved. Large scale trade of hair from wild goats hunted for meat or trophy and hybridisation of wild (Capra ibex) and domestic (Capra hircus) goats or wild Vicuna (Lama vicugna) and domestic Alpaca (Lama pacos), with the aim of improving fibre fineness and yield, would involve a risk of genetic pollution and would severely threaten conservation and biodiversity. This work describes fibre morphology and cell structure of fine fibres from the most important wild and domestic fibre producing species with the aim of enhancing traits for identification purposes. Microscopy investigation shows that exposure to thermal and nutritional stresses in the wild, lead to finer hair associated with lower rate of growth, yielding orientation and elongation of the cuticle cells. Differential scanning calorimetry reveals specie-specific differences in the internal structure of the fibre cortex, probably related to the process of hair keratinisation.

Evaluating Protein Patterns of Speciality Fibres for Identification to Combat False Labeling

Evaluating Protein Patterns of Speciality Fibres for Identification to Combat False Labeling

Fiber‐optic probes for in vivo depth‐resolved neuron‐activity mapping

Specialty fiber probes are used for in vivo depth-resolved mapping of neuron activity through the optical detection of fluorescent-protein reporters expressed inside the living brain of anesthetized transgenic mice. Supercontinuum radiation produced by highly nonlinear photonic-crystal fibers is employed to demonstrate a simultaneous multicolor interrogation of several biomarkers in a model aqueous solution system, thus suggesting the way toward a multiplex mapping of various types of neuron dynamics inside the living brain.

Two-beam multiplexed CARS based on a broadband oscillator

A two-beam multiplexed coherent anti-Stokes Raman scattering (CARS) microscopy setup is demonstrated by using a broadband (BB) Ti:sapphire oscillator without using any specialty fibres. A well-defined spectral structure of the source leads to a delay-sensitive CARS measurement in two-colour CARS and also provides an efficient means of obtaining three-colour CARS signals combined with the dispersion compensation of the BB pulse. Our result implies that the background suppression is limited by the onset of the spurious signals caused by the different CARS process, qualitatively differing from what is typically observed in the CARS microscopy. Copyright © 2010 John Wiley & Sons, Ltd.

Effects of Laundering and Water Temperature on the Properties of Silk and Silk-blend Knitted Fabrics

The objective of this work was to review the properties of selected specialty protein fiber knit fabrics suitable for everyday wear. Selected properties (dimensional stability to laundering, mass, thickness, and stitches per centimeter) of three commercially available fabrics were measured when new and after each laundering cycle (1—6). The silk and silk-blend fabrics achieved dimensional stability by six laundering cycles. Fabric properties differed with the number of laundering cycles, fabric color, and fabric type. Although water temperature affected the pattern of change of some properties, it had no overall effect on properties of the stabilized fabrics. However, examination of new and washed fabric using scanning electron microscopy suggested fibrillation and degradation of silk fibers may be affected by laundering.