Majlesi Journal of Telecommunication Devices Vol. 6, No. 3, September 2017 77 Design of an All- Optic Communication Filter Based on Photonic Crystal Structure Majid Malekian, Hossein Emami, Mohsen Ashourian Department of Electrical Engineering, Majlesi Branch, Islamic Azad University, Isfahan, Iran. Email: majid.malekian63@gmail.com, h.emami@iaumajlesi.ac.ir (Corresponding author), ashourian @iaumajlesi.ac.ir Received: March 2017 Revised: June 2017 Accepted: August 2017 ABSTRACT: One of the structures made of photonic crystal is all-optic filter which these filters are widely used in optic telecommunications systems and networks. In this paper, a method has been presented to design an optic filter based on two-dimensional photonic crystals. The crystal which we suggested, was obtained by FDTD and PWE numeric methods, that influenced different parameters of output wavelength of filter. The result showed that increase of refraction index of Dielectric, leads information in output wavelength of filter. KEYWORDS: All- optic filter, Photonic crystal, FDTD, PWE. 1. INTRODUCTION Expanding communication and the simplicity of data transfer through transfer systems and optic fiber is one of the important cases of today communications. The speed, suitable quality and transfer simplicity in transferring signals containing digital information is one of the most important features of communication through optic fiber. The optic communication may be investigated in three general parts including optic sender (Transponder), optic fiber, and optic receiver. The sender (transponder) part sends the information in the form of light. This information is transferred to destination by optic fibers, and is decoded in receiver part. Demand for new services leads increase in speed and volume of sending information incredibly in recent years. For this reason, all- optic systems and optic integrated circuits are of practical and interesting subjects which are the background of different researches. In an all-optic communication, processing the optic information is done by optic devices, and the optic signal does not change to electric signals. The photonic crystals are the best options to design all- optic pieces. The photonic crystal is a structure with frequency coefficient. If the frequency is in one dimension, the photonic crystal will be one-dimensional and if it is the repeat of structure in two or three dimensions, the photonic crystal will be two-dimensional and three- dimensional. The different crystal structures represent a wide range of physical features because of having different electrical structures. While entering light into photonic crystal structure, the diffusion takes place in special frequencies because of its structural features and electrical characteristics. This is called the allowed range. When the diffusion does not take place in a range of special frequencies sit forms unallowable range which is called forbidden band. One of the structures made of photonic crystal is optic waveguide which has the ability of transferring optic photonic pulses from one point to the other point. The photonic crystal waveguides may be created by creating network defects. In this paper, a new structure is formed for all- optic filter of photonic crystal as two sense ring- one of the advantages of this structure is the capability of configuring exacerbated wavelength. The simulation and analysis of structure have been done by plane wave expansion (PWE) and finite difference time domain (FDTD) methods. This paper continues as follows that the first discussion is about the importance of subject and a short background is stated then the process of designing filter is investigated, in next part we deal with simulation and finally we discuss about the results.