Mir Ali Ghasemi, Reza Khodadadi, Hamed Alipour Banaei / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 6, November- December 2012, pp.960-968 960 | P a g e Design And Simulation Of All Optical Multiplexer based On One-Dimensional Photonic Crystal For Optical Communications Systems Mir Ali Ghasemi * , Reza Khodadadi ** , Hamed Alipour Banaei *** *(Department of Electrical Engineering, Ahar Branch, Islamic Azad University, Ahar, Iran.) ** (Department of Electrical Engineering, Ahar Branch, Islamic Azad University, Ahar, Iran. ) ***( Electrical Department, Faculty of Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran.) ABSTRACT In this study a four-channel multiplexer of Dense Wavelength Division Multiplexer (DWDM) has been designed and stimulated by one-dimensional photonic crystal structure to be used in optical telecommunication purposes of C band. It has been formed of both Germanium and Silicone crystals based on grading method of refraction factor profile (Apodization). In this process by means of Transfer Matrix Method (TMM), light refraction theorem and defect exertion, the effect of radiated optical signal angle to studied structure and optical multiplexer has been made by too narrow channels. Keywords- C band , Multiplexer , Photonic crystals , Transfer Matrix Method (TMM) I. INTRODUCTION Since, access to high speed and capacity in transmitting and receiving data is under the attention of researchers, optical telecommunication systems has been considered based on laser and optical fiber. Therefore in this kind of structure, by making all devices optical, we can remove the problem of low speed in systems that use electric signal [1], [2]. These all optical networks can be replaced by present optical fiber systems that are optoelectronic segments. In this condition, we have to use the technology of all optical networks [3], [4]. So "photonic crystals" usage matter is presented, these crystals because of having unique linear and nonlinear features are used in optical communications [5]. This naming reason is related to their periodic structure and function in light. In fact, they are periodic items of dielectric materials that optical waves (electromagnetic) can`t pass through them in special frequency spans, this area is called photonic gap band [6], [7]. So by breaking the alternative period of photonic crystal, we can engineer light diffusion into it. For example, we can make some changes in band structure of photonic crystal by defect to make optical waveguide with less loss [8] , optical switches [9] , filters , resonators , multiplexers and optical demultiplexers for wavelength division multiplexer (WDM) networks [10]-[16]. Since multiplexers and demultiplexers are from required basic blocks, for combing and separating a great number of channels in WDM networks, we studied four channel optical multiplexer and tried to decrease the channel width of data transmission as far as possible. So by making all equipment optical, we can increase the speed and capacity of data transmission in communication industry. In this section, at first we will discuss multiplexing method and then will study suggested structure. A. DWDM and CWDM methods contrasts The method of wavelength division multiplexer (WDM) is used as main method in data transfer of optical systems [19]. In this method, several optical signals are combined to each other and then are amplified and transmitted as a collection. It leads to increase in data transfer capacity. So one of the advantages of this method is the ability in transmitting a lot of optical channels in different formats by one fiber and each channel can transfer 2.5 Gb/s or more data [20], [21], diagram block of this process has been showed in figure 1. Amplifiers that amplify optical signals without converting to electrical signals have made WDM too valuable and useful. Fig.1 Structure of wavelength division multiplexer  Multi_channel WDM operation  Date-rate and modulation-format transparent  One optical amplifier ( per fiber ) supports multiple channels  80-140 km amplifier spacing  Distortion and noise accumulate ( OA )