Abstract: Innovations in optical fiber technology are revolutionizing world communications. As we can se that optical fiber long period grating can be used in designing of devices which are used to meet the growing demands for various ranges in the field of optical communication systems. Thus, this paper deals with the descriptive study of long period fiber grating (LPG) and its applications in emerging field of optical communication systems. LPG forms an important component of optical communication. The paper covers the analysis of long fiber grating and their fabrication. This paper also deals with the cladding mode analysis of the fiber which describes the inaccuracies of two layer model of the fiber and implementation of three layer fiber geometry to calculate the effective refractive index of the fiber so that it can effectively couple the signal for its efficient transmission. In the cladding mode analysis the whole mathematical derivation along with the requisite mathematical expressions are explained to find the effective refractive indices of the various cladding modes being supported by the fiber which are used to plot the transmission spectrum of the LPG designed for a particular frequency or wavelength used for telecommunication purposes.

Keywords: Optical Fiber Communication, long period Grating, Optical Filter, coupled mode equations, LPG fabrication.