Graded-index Core Research Articles

An analytical model for studying two-mode fibers: Splice loss prediction

In this paper we present a simple analytical model for the modal fields of an arbitrary graded index core two mode fiber and use it to study loss and mode conversion at a splice. The model is simple enough to obtain the modal field distributions and predict splice loss across jointed two-mode fiber links within a few percent accuracy on a pocket programable calculator.

Cutoff frequencies of vector wave modes in cladded inhomogeneous optical fibre

Asymptotic vector wave formulas for calculating the cutoff frequencies in optical fibres with graded-index core and uniform cladding are derived. Numerical examples are given in comparison with the scalar wave solutions, in order to show that the mode degeneracy present in the regime of scalar wave approximations is removed and the cutoff values in degenerate states split slightly.

Modal dispersion of optical fibres with a composite α-profile graded-index core

It is shown that refractive-index profiles with different values of a in different annular regions of the core cross-section make it possible to achieve an almost flat r.m.s. spectral response over a spectral region of several hundred nanometres.

Atlanta Fiber System Experiment: Reproducibility of Optical Fibers Prepared by a Modified Chemical Vapor Deposition Process*

The reproducibility of low-loss glass-fiber optical waveguides prepared from preforms produced by a “modified” chemical vapor deposition process was determined. The fibers have a multimode, graded-index core of germania borosilicate glasses and a cladding of fused silica. The quality of the fibers is expressed in terms of core/cladding dimensions, circularity, and concentricity, as well as loss spectrum, normalized index-of-refraction difference Δ, and graded-index profile characteristic α.

New glass system for low-loss optical waveguides

Optical fibres have been made by the vapour deposition of P2O5-GeO2-SiO2 glass onto the inside surface of Corning Code 7913 glass tubes. These graded-index core waveguides exhibit low attenuations, i.e. 4.0 dB/km at 0.82μm.

Mode Coupling Effects in Graded-Index Optical Fibers

Mode coupling theory is applied to the study of multimode optical fibers with graded-index cores. For coupling caused by random bends in the waveguide axis, the results predict the dependence of the induced losses on the fiber's characteristics. The impulse response is determined for fibers with random bends having several different power spectra. The results are used to predict the transmitted power, the delay time, and the rms pulse width in fibers with graded-index cores.

Propagation characteristics of multimode fibers with graded core index

Bending loss and impulse response of multimode fibers with graded-index core have been studied. A multimode fiber which has a large index difference is profitable because of low loss in bends. Impulse response of the fiber in which all of the possible modes are excited with the same intensity depends remarkably on the fourth-order term of the index profile. A small value of mode delay of 0.15 ns/km is estimated to be obtainable in a fiber having an optimum index profile and index difference ratio of 0.05 using incoherent light.