Performance evaluation of frequency-coded optical code division multiple access.

Hamza Mohammed Ridha Yahya
Dr. Ra'ad S. Fyath

Abstract: Optical code division multiple access (OCDMA) is used recently as access method in optical fiber networks without the need for traffic management or system synchronization. It takes advantage of the sporadic use of channels by allowing many users to be simultaneously connected to the network. Among OCDMA systems, frequency-encoded optical code division multiple access (FE-OCDMA) deserves close attention because it solves many obstacles which appear in conventional OCDMA systems such as multiple access interference (MAI). In this work, an incoherent FE-OCDMA systems are modeled. The probability density function (PDF), bit error-rate (BER) performance, and the spectral efficiency of FE-OCDMA systems are evaluated in the present of optical, shot and receiver thermal noise. Practical parameters are chosen in measuring system's performance. The modeling and calculation programs are carried out on MATLAB7 software running on Pentium 4 workstation with Intel processor 1.7 GHz. The performance of m-sequence, bipolar Hadamard, modified quadratic congruence (MQC) and balanced incomplete block design (BIBD) code families' is evaluated and compared according to the results obtained. The results indicate clearly that the m-sequence and bipolar Hadamard code families can achieve high signal-to-noise ratio (SNR) as compared with MQC and BIBD code families. Furthermore, for BER =10-10, the MQC and BIBD codes lead to 8.4 dB spectral efficiency advantage as compared with m-sequence and bipolar Hadamard codes when NU =100.