Symmetric Fiber Research Articles

Rapid Automatic Index Profiling of Whole-Fiber Samples: Part I

A new interferometric method not requiring any sample preparation is presented for determining the refractive-index profiles of optical fibers. The whole fiber is immersed in index-matching oil and placed transversely under an interference microscope. The determination of the refractive index distribution for an arbitrary, circularly symmetric fiber core requires the solution of an integral equation. In this first of two papers on the subject, we describe a method which accomplished its solution by assuming that the fiber core consists of a large number of concentric circular cylinders of step-wise constant refractive index. The index distribution can then be obtained by determining the index values of each layer successively. The method has been applied to double- and single-pass interferometric arrangements which are being compared here. The single-pass method is reproducible to about 1 percent and provides the complete index distribution within minutes with the help of a computer-controlled video-analysis system. The results of this method are in excellent agreement with profiles obtained from polished slabs of the same fiber.

Ray theory of randomly bent multimode optical fibers

The complete solution for propagation in randomly bent, circularly symmetric multimode optical fibers is given; the paraxial-ray-optics approximation is used. This ray-optics solution is, in principle, equivalent to the power-coupled-mode equations in the continuum limit. However, none of the assumptions usually made in modal theories is needed in the ray theory. In particular, the coupling between nonadjacent modes is effectively taken into account.

Strength and elastic response of symmetric angle-ply cfrp

Comparisons between experimentally determined strengths and the theoretical predictions using four simple failure criteria are presented for symmetric angle-ply carbon fibre reinforced plastics laminates under tensile and compressive loads. The effects of non-linearity and failing strain are considered, and a correlation is given between the non-linear behaviour of unidirectional material subjected to shear and the non-linear elastic response of balanced angle-ply test specimens under tension.

Optimum profiles for dispersive multimode fibres

A simple closed-form expression is given for the index profile of multimode fibres with arbitrary dispersion providing transmission capacities as large as 1.6/Δ 2 Mbit/s km, whereΔ≡Δn/n. Our result reduces to a previous result of Marcatili for the special case of circularly symmetric fibres. A transmission capacity of 150 Mbit/s over a 10 km long fibre appears possible with LED sources operating at optimum wavelengths for the medium.

Virus concentration using hollow fiber membranes—II

An asymmetric polysulphone hollow fiber membrane permeator was used to concentrate polio I virus from 5 and 50-L of deionized- and tap-water. The objective of the study was to evaluate the effect of several independent variables—membrane type and morphology, initial virus concentration, initial feed volume, feed water type and backwash recovery of virus—on process performance. Also, it was the purpose of this study to compare performance for the asymmetric polysulphone and semidense symmetric cellulose acetate hollow fiber membranes (Belfort, Rotem and Katzenelson, 1975). From the results presented here and from a general chemical and biological stability point of view, the polysulphone membranes were superior for virus concentration. The module tested here proved to be versatile and continuously reusable. Finally, in no case and under all conditions studied was polio I virus detected in the permeate.

Optimum profiles for dispersive multimode fibres

We give a simple closed-form expression for the index profile of multimode fibres with arbitrary dispersion that provides transmission capacities as large as 1.6/Δ2 Mbit/s×km, where Δ ≡ Δn/n. Our result reduces to a recent result of Marcatili for the special case of circularly symmetric fibres. A transmission capacity of 150 Mbit/s over a 10 km-long fibre appears possible with l.e.d. sources

Dispersion in optical fibres with stairlike refractive-index profiles

In multimode circularly symmetric fibres whose index distribution is a stairlike approximation of an optimum profile, the modal dispersion increases as the number of steps decreases. For a fibre with Δn/n=0.02 and a core radius of 40 μm, numerical calculations based on wave optics show that the r.m.s. impulse response width at λ=1 μm increases from 0.075 ns/km for the smooth optimum profile to 0.23 ns/km for 40 steps of equal areas. Thus an important conclusion of the analysis is that one should avoid introducing steps in the refractive-index profile of fibres for optimum results.

Scattering of waves with normal amplitude distribution from cylinders

The scattering of waves with a Gaussian amplitude distribution from perfectly conducting and radially inhomogeneous dielectric cylinders is presented. The plane wave scattering solution is obtained as the limiting case when the radius of the scatterer is much smaller than the size of the wave. The scattering of beam waves from spherically symmetric particles was considered recently by Morita et al. [1]. In this communication the case of scattering of waves with a Gaussian amplitude distribution from cylindrically symmetric and infinitely long targets is considered. In a future contribution the scattering of beam waves at normal and oblique incidence from cylindrically symmetric fibers will be reported.

Optimum fibre orientations for the buckling of thin plates of composite material

Abstract Optimum symmetrical fibre orientations are derived for thin plates of fibre-reinforced material to resist buckling under compression or shear. Design charts are plotted for the buckling coefficients in each case, and a parameter is introduced which relates the maximum stress in the reinforcing fibres to the buckling stress of the plate.