Malaysia, Malaysia
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Ahmed H.Y.,Salam University | Elmaleeh M.,University of Gezira | Fadhil H.A.,University Malaysia Perlies | Aljunid S.,University Malaysia Perlies
International Arab Journal of Information Technology | Year: 2013

In this paper, a new code structure with ideal in-phase cross-correlation for the Spectral-Amplitude-Coding Optical Code-Division Multiple-Access (SAC-CDMA) system called Vectors Combinatorial (VC) code is proposed. VC code is constructed using Euclidian vectors and a simple algebraic way for any positive integer number based on the relationship between the number of users N and the weight W. We have also studied the performance of OCDMA systems using a newly proposed Direct Recovery Scheme (DRS) under various link parameters. The impact of the detection techniques and data rate effects on the Multi-User Interference (MUI) is reported using a commercial optical systems simulator, Virtual Instrument Photonic (VPI™). The VC code is compared mathematically with other codes which use similar techniques. We analyzed and optimized the data rate, fiber length, and channel spacing in order to reduce the BER effect. A comparison between Complementary and DRS techniques for theoretical and simulation results taken from VPI™ is demonstrated. It is verified that, for a high data rate (higher than 2.5 Gb/s), even if dispersion compensated devices are not deployed, the BER can be significantly improved when the VC code with desired parameters are selected using DRS technique. Also it is found that as the channel spacing width goes from very narrow to wide, the BER decreases and best performance occurs at a spacing bandwidth between 0.8 and 1 nm. In addition, we have shown that the proposed new DRS technique utilizing VC code significantly improves the performance compared with the conventional SAC Complementary subtraction technique.


Ahmed H.Y.,King Khalid University | Almaleeh M.,University of Gezira | Fadhil H.,University Malaysia Perlies | Aljunid S.A.,University Malaysia Perlies | And 2 more authors.
Optik | Year: 2012

This paper investigates the performance of vector combinatorial (VC) code for spectral amplitude coding optical code-division multiple-access (SAC-OCDMA) system using a newly proposed subtract exclusive OR detection (SED) technique. VC code is constructed using Euclidean vector and algebraic ways. One of the important properties of this code is that the maximum cross correlation is one, which means that multi-user interference (MUI) and phase induced intensity noise (PIIN) are reduced. The weight for the VC code can be any positive integer number. The system performance was evaluated by comparing the theoretical studies using related equations and simulation results taken from the commercial optical systems, "VPI™ TransmissionMaker 7.1". Significant improvement in system performances has been observed when the proposed SED technique employing VC code was applied compared to other codes that utilize conventional balance detection techniques for spectral amplitude coding. © 2011 Elsevier GmbH. All rights reserved.


Ahmed H.Y.,Salman bin Abdulaziz University | Almaleeh M.,University of Gezira | Fadhil H.,University Malaysia Perlies | Aljunid S.A.,University Malaysia Perlies | And 2 more authors.
Journal of Engineering Science and Technology | Year: 2012

The intent of this paper is to study the performance of spectral-amplitude coding optical code-division multiple-access (OCDMA) systems using Vector Combinatorial (VC) code under various optical parameters. This code can be constructed by an algebraic way based on Euclidian vectors for any positive integer number. One of the important properties of this code is that the maximum cross-correlation is always one which means that multi-user interference (MUI) and phase induced intensity noise are reduced. Transmitter and receiver structures based on unchirped fiber Bragg grating (FBGs) using VC code and taking into account effects of the intensity, shot and thermal noise sources is demonstrated. The impact of the fiber distance effects on bit error rate (BER) is reported using a commercial optical systems simulator, virtual photonic instrument, VPITM. The VC code is compared mathematically with reported codes which use similar techniques. We analyzed and characterized the fiber link, received power, BER and channel spacing. The performance and optimization of VC code in SACOCDMA system is reported. By comparing the theoretical and simulation results taken from VPITM, we have demonstrated that, for a high number of users, even if data rate is higher, the effective power source is adequate when the VC is used. Also it is found that as the channel spacing width goes from very narrow to wider, the BER decreases, best performance occurs at a spacing bandwidth between 0.8 and 1 nm. We have shown that the SAC system utilizing VC code significantly improves the performance compared with the reported codes. © School of Engineering, Taylor's University.

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