Silica Glass Fiber Research Articles

Simulation of interferometric sensors for pressure and temperature measurements

A Mach–Zehnder type fiber optic sensor is modeled and the phase change for this device as a result of pressure or temperature variation is studied. Different parameters involved in the sensing process such as Young's modulus, Poisson's ratio, light wavelength, index of refraction, and stress–optic coefficients are changed and their effects investigated. Our results show that Young's modulus, Poisson's ratio, light wavelength, and stress–optic coefficients have the major roles for pressure sensing. On the other hand for temperature sensing, light wavelength, thermal expansion coefficient, and temperature dependence of the index of refraction are the important parameters. For a typical silica glass fiber at 0.6328 μm wavelength, the calculated phase change due a pressure change of 1 Pa for the 1 m length is 4.08×10−5 rad. This phase change for 1 m of a similar probe fiber corresponding to 1 °C temperature change is found to be 107 rad.

Spinnability and crystallizability of silica glass fiber by the sol–gel method

In this paper, the authors report an investigation into the effects of the addition of amounts of H 2O and HCl on the spinnability and crystallizability of silica glass fiber by the sol–gel method. The spinnability of TEOS sol was dependent on the structure characteristics, which were controlled by the amount of H 2O and HCl. If a lineal structure (Si–O–Si) dominated in the sol, the sol exhibited excellent spinnability. The crystallizability was determined by structure characteristics of the Si–O–Si and the content of broken bond. It was easy to crystallize the SiO 2 glass fibers with a three-dimensional network structure and a low content of broken bonds. The optimum amount of H 2O and HCl with excellent spinnability and poor crystallizability was 1.5 and 0.03 mol ratio, respectively.

Comprehensive theory of dispersion in graded-index optical fibers

This paper presents a theoretical investigation on the dispersion in graded-index silica glass fibers under overfilled launching with equal excitation of modes. This theory incorporates both chromatic effect and modal contribution which takes not only the modal delay into account but also the distributed loss and mode-coupling. Random microbends are considered to be the most dominant source of coupling. All index perturbations and intrinsic core diameter variations are assumed to be negligible, but they could readily be included without changing the basic structure of the model. The 3-dB bandwidth is analyzed through the study of the fiber transfer function which introduces the wavelength and modal effects as two separate filter functions. The formal derivation of the chromatic transfer function is analytical. On the other hand, the modal transfer function is obtained by numerically solving the power flow equation in the frequency domain using Crank-Nicholson method. As an application, the results are illustrated showing, in particular, the influence of the fiber core/outside diameters, for the first time.

Fibre Optics and Dissemination of Information

The picture featured on the cover of this issue depicts light being transmitted by fibre optics. Fibre optic technology is used to link computers within local area networks, is the basis of endoscopy, and has virtually replaced copper wire in long-distance telephone lines. Fibre optic cable consists of hair-thin glass fibres (typically 0.125 mm diameter). Currently, the purity of silica glass fibres is such that infrared light in the wavelength ranges of 0.8 to 0.9 m or 1.3 to 1.6 m can travel for 100 km or more without the need for boosting by repeaters. These wavelengths are efficiently generated by lightemitting diodes or semiconductor lasers and suffer the least signal attenuation in glass fibres. As pharmacists, we depend on the efficient transmission and dissemination not of light, but of information. Having accurate, up-to-date information is critical to our work. Ensuring its availability is particularly tough in some instances, most notably for disease caused by the human immunodeficiency virus, where changes in therapy occur so rapidly that keeping up is often difficult. But keeping up and knowing what is right and true become impossible when information is withheld. The 1990s brought dramatic changes to the pharmaceutical industry, mergers being the most obvious. However, during this period there was also a change in

Measurement and calculation of electrostrictive effects in a twin-hole silica glass fiber

A precise method for evaluating the electro-optic coefficients of an optical fiber is introduced. The method was used to characterize the third-order nonlinearity of twin-hole silica fibers. The polarization dependence expected for isotropic materials and the Kleinmann symmetry condition was not observed. We explain the lack of polarization dependence of the third-order tensor by taking into account the electrostrictive contribution to the quadratic electro-optic effect.

Direct Fluorometric Analysis of PAHs in Water and in Urine Following Liquid Solid Extraction

A method for the determination of PAHs in aqueous media based on synchronous fluorescence analysis directly on a solid phase after extraction was evaluated. Tests were conducted for (i) the simultaneous analysis of naphthalene, phenanthrene, anthracene, and pyrene in water at a parts per billion concentration level using a 0V1 sorbing phase block and (ii) the analysis of 1-hydroxyphenanthrene (1-OHPh) and 1-hydroxypyrene (1-OHPy) in human urine using a small sheet cut from a C18 silica fiberglass extraction disk (ENVI-Disk). Because the linear dynamic concentration range is dependent on both the immersion time and the concentration range, in all cases, an optimum immersion time must be determined to preserve linearity of intensity versus concentration. Calibration curves were determined for a concentration lower than 15 ppb in the case of 1-OHPh and at a concentration lower than 1.5 ppb in the case of 1-OHPy. In all cases the limits of detection were estimated to be lower than 0.2 ppb, i.e., for 1-OHPh and 1-OHPy, in the lowest concentration limit these metabolites were found in the urine of persons unexposed or weakly exposed to PAHs.

Efficient amplification using the /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 9/2/ transition in Nd-doped silica fiber

Amplification characteristics of the three-level /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 9/2/ transition in Nd-doped silica glass fiber are investigated under strong signal saturation and high pump power (150 mW). Aluminum codoped Nd-silica fibers exhibit strong superfluorescent behavior in the four-level /sup 4/F/sub 3/2//spl rarr//sup 4/I/sub 11/2/ transition which limits the optical conversion efficiency into the three-level transition. Ge-doped silica fibers do not exhibit this limitation and can efficiently amplify in the three-level transition with current laser-diode pump technology.

Improvement of the ultraviolet-proof property of silica glass fibers for ArF excimer-laser applications

The effects of preirradiation by ArF excimer laser and thermal annealing on the transmission properties of a silica fiber were investigated. The durability of the fiber when it was exposed to ArF excimer laser irradiation was improved by preirradiation at room temperature and subsequent thermal annealing at 600 degrees C.

Crystallization Kinetics of Mullite in Alumina–Silica Glass Fibers

The mechanism of mullite crystallization in Al2O3‐SiO2 glass fibers with compositions of 49 and 69 mass% Al2O3 was investigated using isothermal methods. The activation energies (Ea) of the nucleation and nucleation‐growth of mullite were obtained from the temperature dependence of the incubation times and rate constants of mullite formation, respectively. The formation of mullite in both glasses occurred in two stages. The amount of mullite increased very steeply in the first stage within very short firing time, whereas the increase was more gradual in the second stage. The Ea values for nucleation and nucleation‐growth in the first stage were 864 and 1288 kJ/mol in the 49‐mass%‐Al2O3 glass fiber and 980 and 1138 kJ/mol in the 69‐mass%‐Al2O3 glass fiber, respectively. Arrhenius plots of the second‐stage data showed that the slope ratios were different at temperatures below and above 1200°C. The Ea values at <1200°C were 1195 and 1099 kJ/mol in the 49‐ and 69‐mass%‐Al2O3 glass fibers, whereas those at >1200°C were 696 and 645 kJ/mol, respectively. Observation of the microstructures and crystallite‐size data indicates that the crystallization of mullite proceeds via three different mechanisms: nucleation, nucleation–growth, and coalescence of mullite grains.

Interfacial bonding of silica glass fiber to polystyrene ionomers

Interfacial bonding of silica glass fiber to polystyrene ionomers

Observation of energy-distribution-dependent homogeneousupconversion in erbium-doped silica glass fibres

It has been demonstrated experimentally that the rate of homogeneous upconversion in erbium-doped fibres increases with increasing pump and signal power, even if the same degree of excitation is maintained. This is due to an increased redistribution of excitation energy among erbium ions by absorption and stimulated emission. A signal of 8.6 mW could more than double the upconversion rate in a densely doped fibre.

Mortality from nephritis and nephrosis in the fibreglass manufacturing industry.

OBJECTIVES: To investigate the question of whether there is an association between exposure to silica or respirable glass fibre and mortality from nephritis or nephrosis among workers in fibrous glass...

A new system for a combined laser and ultrasound application in neurosurgery

A new combined Laser and Ultrasound Surgical Therapy (LUST) device suitable for endoscopical coagulation and tissue fragmentation has been developed at the LMTB1. The new feature is the simultaneous transmission of laser radiation and ultrasound via flexible silica glass fibers. The ultrasound tissue interaction is based on the well-known CUSA-technology which enables the surgeon to cut various types of tissue with different degrees of effectiveness. Application fields are in oncology, neurosurgery and angioplasty. The laser radiation can be used, for example, for tissue coagulation purposes. With a fiber based LUST-system working at a frequency of 30kHz, a displacement of 100pm could be attained at the distal end. (The usual standard CUSA displacement is 10-350 pm.) During in vitro experiments the following tissue fragmentation rates could be achieved: brain tissue 50 mgsec~1, liver 4.5 mg sec-1 and kidney 4 mgsec~1 (displacement of the tip 60 pm; 0 1.3 mm; suction setting: 5 W). Laser radiation up to 25 W was sufficient to coagulate soft tissue. This technology offers new possibilities in minimal invasive surgery. The flexible opto-acoustic waveguide (0 400-1700pm) can be bent making areas accessible that were previously inaccessible. Without changing the instrumentation the surgeon can use the laser radiation for tissue coagulation or cutting and the ultrasound for tissue fragmentation and tissue reduction. [Neurol Res 1999; 21: 84-88]

Effect of uniaxial stresses on silica glass structure investigated by IR spectroscopy

To understand the structural change of silica glass caused by an applied uniaxial stress, the IR reflection peak shift of the silica structural band of a silica glass fiber due to a bending stress was measured. The peak shift is due to a change in the Si–O–Si bond angle. Past measurements by Raman spectroscopy showed that the structural band at ≈1050 cm −1 shifted to a lower wavenumber under tensile stress indicating that the Si–O–Si bond angle decreases under such a stress, while the opposite is expected from the volume change of silica glass by stress. We found that the observed anomaly is an artifact due to the non-uniform structure of the silica glass fiber near the surface layer and once the non-uniform layer was removed, the IR peak shifted in a normal manner and the Si–O–Si bond angle increased under tensile stress.

Photonic band gap guidance in optical fibers

A fundamentally different type of optical waveguide structure is demonstrated, in which light is confined to the vicinity of a low-index region by a two-dimensional photonic band gap crystal. The waveguide consists of an extra air hole in an otherwise regular honeycomb pattern of holes running down the length of a fine silica glass fiber. Optical fibers based on this waveguide mechanism support guided modes with extraordinary properties.

Surface relaxation as a mechanism of static fatigue of pristine silica glass fibers

Mechanical strength degradation of glass under static stress, or static fatigue, is usually attributed to the slow growth of a surface flaw. But some glasses, such as pristine silica optical fibers, can be made free from any surface flaw and yet they exhibit static fatigue. Since pristine glass possesses no crack to grow, an alternative mechanism is needed to explain the static fatigue. Surface structural relaxation is proposed as a fatigue mechanism of such materials. Tensile stress-accelerated surface relaxation kinetics in moist atmosphere were analyzed to obtain the activation volume and the proposed surface relaxation mechanism was shown to be plausible.

Bistability and hysteresis of solitons in inhomogeneously doped fibers with saturating nonlinearity

Inhomogeneous doping of a silica glass fiber is proposed to have bistable soliton propagation. The properties of the solitons in one of the possible models are studied and interpreted.Received 5 June 1997DOI:https://doi.org/10.1103/PhysRevE.58.5021©1998 American Physical Society

Glass fibres of pure and erbium- or neodymium-doped yttria–alumina compositions

Optical fibres doped with lanthanide or transition-metal elements can serve as in-line lasers and amplifiers for fibre-optic telecommunications systems. In general, most such fibre lasers use conventional silica-glass fibres doped with erbium or neodymium. But silicon dioxide absorbs strongly in the infrared for wavelengths of greater than 4 µm or so, limiting the infrared range over which such lasers can operate. Some other oxide materials do not absorb significantly until longer wavelengths—the absorption coefficient of crystalline silica at 4 µm is equal to that of yttrium oxide at 7.1 µm and of sapphire (a form of alumina) at 5.1 µm, for example1. Glass fibres made from these materials would therefore expand the range of fibre lasers into the mid-infrared. But molten oxides that do not contain silica typically have a viscosity too low to support fibre-pulling processes. Here we demonstrate that containerless processing, in which a molten sample is levitated by a flow of inert gas, permits sufficient undercooling of molten yttrium aluminium garnet (YAG:Y3Al5O12) to access a viscosity range conducive to fibre-pulling. The process is particularly effective if the molten material of stoichiometric YAG composition is doped with Nd2O3 in place of Y2O3, or with excess Al2O3; and it should also work with other dopants, because molten oxides are good solvents. Fibres could be drawn from a melt doped with Er2O3 in the presence of excess Al2O3. These fibres have the potential to extend the operating range of oxide glass-fibre lasers.

The multicore fiber – a novel design for a diode pumped fiber laser

A multicore fiber serving as the gain medium for a fiber laser is introduced. Nearly 40 monomode cores are fitted into a standard multimode silica glass fiber. The cores are arranged on an annulus situated near the border of the fiber. The multimode fiber guides the pump radiation with which the Nd 3+-doped cores are excited. The pump waveguide was modelled presupposing that the absorption is nearly homogeneously distributed. The lasing properties of this sophisticated design are quite promising giving about 450 mW at λ=1050 nm for a pump power ( λ=805 nm) of 1800 mW and a fiber length of 40 cm. The slope efficiency amounts to 40%. The far field intensity pattern possessing an angular width defined by a single source resembles that of an ensemble of emitters with random phases.

A simple chemical etching technique for reproducible fabrication of robust scanning near-field fiber probes

A two-step chemical etching procedure has been developed for fabricating probes used by scanning near-field optical microscopy. These probes have two tapered regions which can be reproducibly constructed with a wide range of cone angles. The shape of the probe allows it to be used over sample surfaces with deep and narrow regions. Furthermore, our method can be applied to silica glass fibers which are commercially available. To demonstrate, we used these tips to acquire the near-field optical image of a thin layer of polystyrene spheres. Intensity interference patterns were observed. The demonstrated in-plane resolution was estimated to be about 250 nm. This is mainly limited by the diameter of the metal-coated tip. The transmission efficiency of the tip is better than 10−4.