Ahmed Garadi*, Boubakar S. Bouazza, Abdelkader Bouarfa and Khansae Meddah Enhanced Performances of SAC-OCDMA System by Using Polarization Encoding https://doi.org/10.1515/joc-2017-0182 Received October 18, 2017; accepted December 27, 2017 Abstract: This article presents a novel encoder technique of spectral amplitude coded multiple access (SAC-OCDMA) systems. The proposed technique is based on two ortho- gonal polarization states of the same one dimensional optical code. This method is usually applied to increase the number of simultaneous users in a network, and it can double the number of potential users against the one- dimensional code. The results obtained in this work show that optical zero cross-correlation code can accom- modate more users simultaneously for the typical bit error rate of optical communication system of 10 - 9 . Keywords: zero cross-correlation (ZCC), polarization mode dispersion (PMD), differential group delay (DGD), spectral amplitude coded multiple access (SAC-OCDMA) 1 Introduction The optical CDMA is based on the same basic concepts as the CDMA radiofrequency. Assigning to each user trans- mitting data through the transmission medium, which is constituted by an optical fiber, a signature or code sequence identifies the destination receiver. The bipolar codes applied to electrical wireless CDMA cannot be applied to incoherent OCDMA systems because they can- not denote and detect the negative components in bipolar codes, for this reason incoherent OCDMA use unipolar codes (“1” and “0”) to detect the presence of light signal energy (positive quantity) or no light signal energy [1]. The OCDMA suffers also from other types of noises like intrinsic noise sources arising from the physical effects of the system design itself such as relative inten- sity noise (RIN), phase induced intensity noise (PIIN), thermal noise and shot noise [1]. PIIN is closely related to the MAI due to the overlapping of spectral from the different users [1]. The key to an effective OCDMA system is efficient address codes with zero cross correlation (ZCC) to easily distinguish the intended signal from the inter- fering signal and high auto-correlation in order to max- imize the intended signal with respect to the interfering (noise) [2]. Spreading in the spectral domain using one- dimensional (1D) optical code with large user’s number requires a very long code length, thus requiring ultra- short optical pulses and rendering such systems impractical. A “two-dimensional” (2D) OCDMA code structure is one of several ways to overcome this preoccupations; these codes are spread in both domains. Several studies have been conducted on the 2D encoding: times/wavelengths, space/wavelengths and polarization/wave lengths [3]. In this article, we demonstrate a 2D wavelength/ polarization multiplexing encoding and decoding OCDMA system. We generate a 2D code where each chip in a code is assigned a wavelength and one of two orthogonal polarization states, in order to maintained the cross correlation at zero in different states we use ZCC code [4]. This type of coding can increase the number of potential users, compared with 1D OCDMA, by a factor of 2 (double). In this article, we are interested in the proposed 2D optical codes W/P. In Section 2, we will show how these codes have been developed theoretically; we will discuss their properties and interpret system performance. The results obtained by Optisystem 7 and their discussions are given in Section 3. Finally, a conclusion of this work is shown in Section 4. 2 Two-dimensional OCDMA design One effective way to generate 2D optical code is to apply the maturely developed 1D code in a combined wave- length and polarization scheme. *Corresponding author: Ahmed Garadi, Laboratory Technology of Communications, University of Tahar Moulay Saida, Saida, Algeria; Department of Electronics, Faculty of Technology, University of Saida, Algeria, E-mail: garadi20@yahoo.fr Boubakar S. Bouazza, Laboratory Technology of Communications, University of Tahar Moulay Saida, Saida, Algeria Abdelkader Bouarfa, Laboratoire d’électronique de photonique et d’optique (LEPO), Université de Sidi bel abbés, BP 892 Sidi Bel Abbès, Algeria Khansae Meddah, Laboratory Technology of Communications, University of Tahar Moulay Saida, Saida, Algeria J. Opt. Commun. 2018; aop Brought to you by | Göteborg University - University of Gothenburg Authenticated Download Date | 2/5/18 8:01 PM