Search

Optical CDMA (OCDMA) systems have received more attention because CDMA allows many users share the same transmission medium asynchronously and simultaneously with a high level of transmission security. In this paper, we describe the improved performance of the spectrum amplitude coding (SAC) OCDMA system using OFDM technique compare to SCM/SAC-OCDMA system. The theoretical results of proposed system shows that, the new SAC/OCDMA system with OFDM technique provides better performance compare to SCM/OCDMA system based on Random Diagonal Code (RD), the results evaluated based on BER, number of users and weight of code. Thus this system could be one promising solution to the symmetric high capacity access network with high spectral efficiency, reducing the required power and cost effective of broadband access network

Orthogonal frequency division multiplexing (OFDM) is one of the Multi-Carrier Modulation (MCM) techniques that transmit signals through multiple carriers. These carriers (subcarriers) have different frequencies and they are orthogonal to each other. There are different parameters which alter the performance of OFDM system. In this paper, the effect of cyclic prefix length (CP) on optical (OFDM) system is investigated. Although employing a CP as the guard interval is a simple way to combat inter-symbol interference (ISI) and inter-carrier interference (ICI), it reduces the transmission efficiency of the system. The simulation results show the effect of CP length in power receiver, penalty of power and improved the performance based on signal to noise ratio (SNR). In addition, a tradeoff is needed between reduced interference effects and transmission efficiency.

In this paper, we describe the improved performance of the SAC-OCDMA system using OFDM technique compared to SCM/SAC-OCDMA system. The theoretical results of proposed system shows that the new SAC/OCDMA system with OFDM technique provides better performance compared to SCM/OCDMA system based on multi diagonal code (MD), and the results have been evaluated based on BER and number of users for bit rate 1Gb/s and 10 Gb/s . Thus this system could be a promising solution to symmetric high capacity access networks with high spectral efficiency, cost effectiveness, good flexibility and enhanced security, which is candidate for next generation networks.

Explosive growth of bandwidth demand together with advance in latest communication services and emerging applications have inspired interest in optical code division multiple access (OCDMA). The work focuses on analysis and demonstration of two-dimensional (2-D) modified double weight (MDW) OCDMA wavelength-time. The 2-D MDW uses balance-detection for mitigating multiple access interference. The property of cross-correlation results in optimum phase induces intensity noise suppression (PIIN). The proposed code achieves high scalability; below 10-9 BER error floor the code cardinality reaches 254 simultaneous numbers of users which is double the 2-D PDC performance. The lowest effective power (Psr) for minimum optical transmission requirement for smallest number of users is achieved at-17.5dBm. The 2-D MDW OCDMA simulation model is developed to validate the realization of the code for BER and distance performance. The 2-D MDW OCDMA code successfully suppresses PIIN and mitigating MAI which result in high cardinality, reduce Psr and improved distance.