A Study of Bipolar Walsh-Hadamard Coding Method in Optical CDMA Networks

Abstract:

This study analyzes and calculates unipolar and bipolar coded configurations of spectral-amplitude-coding optical division multiple access (SAC-OCDMA) systems by using analytic and simulated methods. The important feature of the SAC-OCDMA systems is that multiple access interference (MAI) can be eliminated by code sequences of a fixed in-phase cross-correlation value. This property can be effectively canceled by multiple access interference by using balance detection schemes. This study uses Walsh-Hadamard codes as signature codes for the unipolar and bipolar schemes. The coder and decoder structures are based on optical filters of fiber Bragg gratings (FBGs). The simulation results of unipolar/bipolar coding structures are first presented by commercial simulation obtained using OptiSystem software. The simulation results show that the bit error rate (BER) through use of the bipolar coding method is superior to the unipolar scheme, especially when the received effect power is large. The eye diagram also shows that the bipolar encoding structure exhibits a wider opening than the unipolar encoding structure.

• Periodical: Applied Mechanics and Materials (Volumes 284-287)
• Pages: 2667-2671
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.284-287.2667
• Online since: January 2013
• Authors: Chih Ta Yen, Wen Bin Chen
• Keywords: Bipolar Coding, Fiber Bragg, Multiple Access Interference (MAI), Spectral-Amplitude-Coding Optical Division Multiple, Unipolar Coding, Walsh-Hadamard Code

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