Implementation of an Optical CDMA Based Modified Walsh Code(MWC)

Abstract

Spectral Amplitude Codes (SAC) is used widely in Optical Code Division Multiple Access (OCDMA) network to eliminate some sort of dominant noise. this appropriate noise would be in the state of the art of Multi Access Interference (MAI). This paper suggests a simulation model for optical code division multiple access system based walsh code. The proposed realization aims to build a Simulation case study of three users and demonstrates the construction of modified Walsh code (MWC) with respect to beat noise, phase incoherent intensity noise and thermal noise. In addition, a complete comparison study has been manipulated according to the performance of the proposed MWC and some existing codes such as: modified frequency hopping (MFH) code, Hadamard (HD) code, modified quadratic congruence (MQC) Code, unipolar Walsh code (UWC) and random diagonal code (RD). Numerical simulations have been introduced and discussed, in order to illustrate the effectiveness of the MWC method to eliminate dominant noise. experimental results have forwarded the research to the following facts; the SNR and BER for MWC under the presence of the previous discussed signal degradation is equal 265.4867 and 1.1504e-10 respectively according to a predefined number of users (150). we present a simulation model of optical code division multiple access system by using walsh code based Matlab graphical user interface for such three users case study. A simulated version has been accomplished by using means of OPTI-SYSTEM simulator based 7 subscribers and an optical fiber length = 10 km as a case study. We have set the simulator specifications as follow; phase 1: transmission phase; photo diode as an optical source, mach-zender interferometer, encoder. Phase 2: receiver phase; splitter, decoder, and photo detector as an optical detector. Accordingly, the minimum bit error was 4.02789e-10 which reflects how efficacy was the proposed modified walsh code.