Mach Zehnder Interferometer for WavelengthDivision Multiplexing Ary Syahriar PusatPengkajian dan Penerapan Teknologi Informasi dan Elektronika Badan Pengkajiandan Penerapan Teknologi e-mail : ary@inn.bpPt.go.id Abstract A theoretical analysis of multiplexing basedon Mach-Zehnder interferometer is presinted. The output characteristics and ITU channel separation variation of an equal arm-length interferometer are analyzed. The theory and numerical simulation results have some direct fu ncti on fo r p r acti caI fab r i cati on of the dev i ce s 1. Introduction In modern communication systems narrow band information services and high-speeddata and video information services are expectedto be integrated in one-cofiununication networks Il]. Wavelength Division Multiplexing (WDM) is believed to be one of the most practical ways to achievetransmission capacities of a few tera bit per second (Tb/s). Devices such as optical filters and wavelength multiplexers (MUXER) and demultiplexers (DEMUXERS), which manipulate optical properties in wavelength domain, are essentialto WDM optical communication systems. One of the most useful device is the Mach ZehnderInterferometer(MZI) l2l. It consists of two 3-dB coupler which has been butt spliced to build the interferometers. The most important parameters in MZI is the difference in path length which basically will determine the MZI's characteristics. In this paper the analysis of MZI basedon coupledmode theory and matrix transmission method is presented. A number of its features will alsobe explained. 2. The MZI Structure A Mach-Zehnder device consistsof two 3 dB fused couplers, between which a phase difference is introduced in the two paths by increasingone of the path lengths with respectto the orher as shown in Figure 1. The fused couplers are wavelength sensitive;hence the characteristics of the device are determinedby the 3 dB crossover wavelength of the couplers, the coupling strength and the introduced path difference. Co ler 2 Input 1 Input 2 OutputI Outout2 up I v Figure I. Schematic diagram of Mach-Zehnder intederometer For modeling purposes the device canbe dividedinto threeconstituent parts:the two 3 dB couplers and a phase shifting section between them.The characteristic of eachof the comporiBnts