<title>Dependence of the dispersion curves of a two-concentric-core optical fiber to the refraction index</title>

Abstract

ABSTRACT Dispersion curves of the modes TE y TM of a two concentric core optical fiber are presented. This fiber, incontrast to multi clad-one, has a layer where it is assumed that guided modes exist. The main characteristic ofsuch a curves is that they are discontinuous.Keywords: concentric core optical fiber, dispersion curves, photonic band gaps 1. INTRODUCTION Many applications in the field of fiber lasers, light-wave telecommunication, medicine, etc., demand devices basedon novel design of optical fibers; the multi-clad fibers play a relevant role in this kind of applications. Recently,high power neodymium-doped multi-clad fiber laser, with a refractive index profile of the so-called M and Wtype have been reported.'We present a novel kind of optical fiber: the so-called two-concentric core optical fiber.2 The geometry ofsuch a fiber is conformed by four layers. The first two layers have a similar structure to that of common fibers.The third layer has similar optical properties, refractive index for example, to that of the central core, due tothese reasons we consider it a concentric core-like and finally, we have the outer cladding. We realize that sucha fiber could propagate radiation in the concentric core, thus this condition is the main difference with otherfibers studied before35