Modal characteristic equation and dispersion curves for an elliptical step-index fiber with a conducting helical winding on the core-cladding boundary - an analytical study

• Published in: Journal of lightwave technology Vol. 20; no. 8; pp. 1416 - 1424
• Main Authors: Kumar, D., Singh, O.N.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01-08-2002; Institute of Electrical and Electronics Engineers; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Applied sciences; Boundary conditions; Circuit properties; Communication system control; Electric, optical and optoelectronic circuits; Electromagnetic scattering; Electromagnetic waveguides; Electronics; Equations; Exact sciences and technology; Integrated optics. Optical fibers and wave guides; Optical and optoelectronic circuits; Optical fiber dispersion; Optical fiber polarization; Optical fibers; Optical propagation; Optical waveguides; Modal analysis; Electromagnetic wave propagation; Dispersion relation; Characteristic equation; Helical structure; Boundary condition; Elliptical waveguide; helical structures in electromagnetic (EM) fields; Optical fiber
• ISSN: 0733-8724; 1558-2213
• DOI: 10.1109/JLT.2002.800799

A special type of elliptical step-index fiber with a conducting helical winding on the core-cladding boundary is proposed and investigated theoretically. Using elliptic cylindrical coordinates, boundary conditions are derived and longitudinal field components for the even and odd modes are obtained. The characteristic equation for the waveguide to be studied is determined by solving the fourth-order determinantal equation, which also contains complex quantities. In order to study the fundamental mode, the modal index /spl nu/ is put as /spl nu/=1. The equations obtained involve modified Mathieu functions of the first order and their derivatives. Applying approximations, cutoff conditions are obtained. Numerical computations are made. Dispersion curves are obtained for different pitch angles of the helical winding.