Dielectric Fiber Research Articles

Analysis of the Hybrid Modes for an Eccentrically Cladded Fiber

This paper examines the hybrid-cladding modes of an eccentrically cladded three-layer dielectric fiber. The solutions are specialized to small eccentricities, and exact closed-form expressions for the normalized deviations of the cutoff wavenumbers from those of the concentric case are determined. Numerical results for various types of hybrid-cladding modes of the fiber are given. For certain values of the parameters, it is possible to enhance the operating bandwidth of the basic hybrid mode HE/sub 11/ over the conventional concentric fiber because its cutoff frequency can be shown to remain zero.

Infrared properties of quartz fibres and wool

This experimental and theoretical study is devoted to the general infrared properties of dielectric fibres and wool with fibre diameters comparable to the infrared wavelengths. Amorphous quartz is used as the fibre material since its bulk infrared dispersion is known, and since it is suitable for the manufacture of thin fibres. Diffuse reflection, extinction and scattering including polarization phenomena of fibres and wools with fibre diameters between 1.8 and 9μm are measured in the spectral region of 400 to 1400cm −1. The measured infrared properties of single quartz fibres agree with the theory of Englman and Rupin. Bulk and surface modes are observed. Thanks to the ideal geometry of the fibres we do not observe the broadening of modes usually reported for small particles. The interpretation of the reflectivity spectra of wool is based on the Kubelka-Munk theory. Multiple scattering prevails. The introduction of an empirical factor connecting the ratio of absorption versus the scattering coefficient with the ratio of the efficiency factors for absorption and scattering allows us to predict in first approximation the spectral reflectivity of dielectric wool samples if the diameter distribution function of the fibres and the bulk i.r. dispersion are known.

Dendritic deposition of uncharged aerosol particles on an uncharged fiber in the presence of an electrical field

A Monte Carlo simulation method based on particle trajectory calculations is used to study the effect of a uniform electrical field on the dendritic deposition of uncharged dielectric aerosol particles on uncharged dielectric fibres. The system parameters are chosen so that the main mechanisms of deposition are interception and electrical attraction. The main electrical force on an oncoming particle is that exerted by the polarized fiber and dendrites. It is found that simple superposition of the electrical fields of the polarized fibre and of the individual deposited particles gives an approximation to the actual field that is adequate for practical purposes. Based on such superposition, particle trajectories are calculated and the dendritic deposition phenomenon is studied. The effects of the electrical field are found to be very important and to increase with increasing field strength. In general, the electrical field increases the number of dendrites per unit length of fibre, and produces dendrites which are long, slender and tend to follow the force lines of the electrical field. The enhancement of the overall rate of deposition is also drastic and increases with increasing electrical field strength.

Enhancement of Fluorescence Induced by Microstructure Resonances of a Dielectric Fiber

Resonance-induced enhancement of fluorescence from a thin dye layer coated on a 9.8-\ensuremath{\mu}m-diam glass fiber has been observed. Enhancement occurs when the wavelengths of incident radiation and/or inelastic emission are resonant with natural modes of oscillation of a circular dielectric cylinder. These dielectric resonances are comparable to surface plasmon resonances in metallic microstructures, which are partially responsible for the surface-enhanced Raman effect.

Scattering of TM Waves by Dielectric Fibres Iterative and Eikonal Solutions

The scattering of electromagnetic waves by dielectric cylinders and, in particular, by optical fibres is studied through integral equations. The convergence of the iterations of the integral equations is established under certain conditions. The latter are satisfied for long wavelengths, and for optical fibres and wavelengths, when the dielectric permeability variation is rather small. An approximate eikonal solution is applied to optical fibres, and its reliability is discussed. A systematic procedure for estimating corrections to the eikonal approximation is proposed.

Transversely incident beam wave scattering from inhomogeneous fibers

An efficient method is employed to determine the scattering characteristics of a beam wave from inhomogeneous dielectric fibers. The fibers are approximated by a series of stratified dielectric layers and only 2 × 2 matrix operations are used. The results apply to an inhomogeneous fiber positioned with its axis of symmetry perpendicular to the direction of propagation of the beam wave. The fiber may have arbitrary, radially symmetric variations of its refractive-index profile. Scattering patterns for several functional dependences of the index of refraction of the fiber are presented.

Fundamental mode propagation on dielectric fibres of arbitrary cross-section

The behaviour of the propagation constants of the fundamental modes on dielectric fibres of arbitrary cross-section is studied by means of a variational formulation of an integral equation for the electric field. The approximate eigenvalue equation which results from the use of a constant trial field within the core is used to generate dispersion curves for several cross-sectional shapes, including rectangular, elliptical and triangular. Agreement with results computed by other methods, where available, is quite good in the single-mode regime.

Measurement of mechanical deformation of dielectric fibres by a light scattering method

This paper describes an experimental method to detect quantitative changes of both refractive index and diameter of unclad dielectric fibres, such as fused silica fibre and nylon 6 fibre, due to tensile stress. The technique employed here is based on the variation in the position of a fringe in back-scattered light, which is generated when a laser beam is incident at a right angle to the axis of the fibre. This procedure makes it possible to measure refractive index, diameter and ellipticity to within an accuracy of 0.048%, 2.6% and 0.05%, respectively.

Optically Powered Speech Communication Over a Fiber Lightguide

The photovoltaic conversion of optical power transmitted over a fiber lightguide can supply electrical power to low-drain semiconductor devices in remote locations. Acoustic powers comparable to those of conventional telephone ringers have been produced <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> in this way by using a fiber-coupled GaALAs photovoltaic detector <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to excite an electroacoustic tone generator. It was conjectured1 that the electrical power for other telephone functions-transmit/receive, dialing, and hook-status recognition-could also be optically supplied, but the signaling techniques appropriate to a dielectric fiber were left unspecified. This note describes the implementation of two-way speech communication between an electrically powered local station and an optically powered station located at the remote end of a 1.1-km-long, single-strand, optical fiber. The remote-station sound alerter has also been operated over this link.

Sensitivity analysis of optical waveguides

The change in the characteristics of dielectric slab and fiber waveguides due to dimensional tolerances of their parameters has been analyzed. The analysis is helpful in fabrication and use of such guides in optical communication systems.

An approximate formula for describing dispersion properties of optical dielectric slab and fiber waveguides

A systematic and analytic approach is made to approximate dispersion properties of dielectric three-layered slab and rod waveguides. The explicit formula obtained yields errors less than 1% except very near the cutoff frequencies of guided modes. The errors diminish rapidly as the normalized frequency increases. The formula has the same expression for slab and fiber waveguides.

Analysis of inhomogeneous multimode dielectric waveguides

A theoretical investigation is made of the characteristics of multimode dielectric fiber waveguides, prepared by deposition from the gaseous phase and characterized by M-shaped radial variation of the refractive index. The WKB method is used to analyze the influence of deviations of the refractive index profile from a parabola on the dispersive properties of the waveguides. These calculations are made for various values of the depth, width, and steepness of a dip of the refractive index which appears at the center of the waveguide because of the evaporation of the dopant. It is shown that the dip increases the spreading of a pulse and accelerates lower-order modes. The optimal shape of the outer edge of the permittivity profile, corresponding to a reduction in the width of the pulse characteristic, is found for a fixed dip of the refractive index.

Measurements of electrical charge on moving dielectric fibers

Measurements of electrical charge on moving dielectric fibers

Scattering from thin and finite dielectric fibers

The electromagnetic scattering from finite-length dielectric fibers with a diameter much smaller than the wavelength and for a perpendicular incidence case is considered. The induced fields are assumed to be uniform on the cross section of the fiber. This yields a one-dimensional integral equation for the inner field which is solved by employing Galerkin’s method. Numerical results for the scattering amplitude are obtained for specific cases. In addition, it is shown that the energy finiteness criterion is satisfied.

Non-spectral Field Representations in Dielectric Fibre Guides

Non-spectral Field Representations in Dielectric Fibre Guides

Light scattering from unclad fibers: approximate ray theory of backscattered light

Formulas have been derived allowing the determination of the parameter ka (k = 2pi/lambda, a is the fiber radius) based on the approximate geometric theory for dielectric nonabsorbing unclad fibers of circular cross section from the course backscattered light intensity. The application of the method is restricted to fibers with the refractive indices within the interval ( radical2,2) and for ka > 100. In this region the method yields results with an accuracy of about 5%.

Field deformation and polarization change in a step-index optical fibre due to bending

The field distribution and polarization state of waveguide modes propagating around a curved dielectric optical fibre are investigated analytically by using a first-order perturbation theory. It is shown that the polarization direction of all modes except the HE1m modes changes due to bending. Field distributions are also deformed and the shift in the field maximum, which takes place in the plane of curvature, is clarified for the dominant HE11 mode.

Correction to "Surface-wave radiation loss from curved dielectric slabs and fibers"

Correction to "Surface-wave radiation loss from curved dielectric slabs and fibers"

On transmission and recovery of three-dimensional image information in optical waveguides*

The paper considers two questions. The first one is: Is it possible to transmit three-dimensional pictorial information through transparent glass (or other dielectric) fibers? We find that due to modal dispersion, pictorial information is invariably “smeared” in transmission. The second question is: Given nature’s reluctance to transmit pictures through fibers, is there anything we can do about it? We suggest that the answer is yes and point to a class of solutions involving nonlinear optical mixing.

Comments on "Radiation from Curved Dielectric Slabs and Fibers" [Letters

In the above paper, Lewin gave an expression for the bending loss of a dielectric fiber with circular cross section. I have shown that the bending loss of arbitrary optical guides can be obtained in a simple manner when the field of the straight guide is known. The purpose of this letter is to show that the results of the two theories are in agreement, except for a factor of 2.