Compensating and equivalence properties of optical waveguides with a linear and sinusoidal variation of the core refractive index and core size along the propagation direction

Abstract

We study two types of variation along the propagation (z-axis) of a step-index fiber. In one case, the core refractive index n1 varies linearly and sinusoidally with the z-coordinate, and in the other, the core radius a varies with z. By a study of the modal characteristics under the weak guidance condition, we show the requisite variation of a with z which will compensate (annul) the variation of n1 with z. This establishes an equivalence of the size variation and core refractive index variation along the z-axis.