JELE_V3_N1_RP2 S.K. Raghuwanshi Mandeep Singh Journal on Electronics Engineering 2249 – 0760 3 1 7 16 Non-Circular Core Fiber, Mode Field Profile, WKB Method, Elliptical Core Fiber, Arbitrary Index Profile Fiber In this paper elliptic cylinder coordinate system is used for the representation of modes in the core of non circular fibre. The scalar wave equation is converted to the elliptical coordinate system and the WKB method is applied for the calculation of fields. The author’s try to develop analytical approach to analyze non circular geometry having an arbitrary refractive index. The result obtained in this paper have been already discussed by the several researcher’s but these research paper lack with the detailed mathematical derivation to achieve some specific equations. The attempts in this paper is to show all the intermediate steps of existing results, which will useful for the beginner, who wants to gain the working knowledge in this area[1]. The result obtained in this paper can be easily extended to obtain the graphical or simulation results for non trivial cases. September – November 2012 Copyright © 2012 i-manager publications. All rights reserved. i-manager Publications http://www.imanagerpublications.com/Article.aspx?ArticleId=2034