1. UKM Learning and Research Repository
2. PHD Thesis / Tesis PHD
3. Institute of Microengineering and Nanoelectronics / Institut Kejuruteraan Mikro dan Nanoelektronik (IMEN)

Title:	Performance And Confidentiality Of A Hybrid Optical Code Division Multiple Access (OCDMA)/Wavelength Division Multiplexing (WDM) Overlay System
Authors:	Isaac A. M. Ashour (P52466)
Supervisor:	Sahbudin Shaari, Professor
Keywords:	Performance And Confidentiality Of A Hybrid Optical Code Division Multiple Access Performance Of A Hybrid Optical Code Division Multiple Access Confidentiality Of A Hybrid Optical Code Division Multiple Access Wavelength Division Multiplexing Overlay System OCDMA WDM Code division multiple access
Issue Date:	12-Apr-2013
Description:	Security systems and multiple access-techniques have been of interest for optical fiber communications for some applications such as military networks and private networks. The combination of both optical code-division multiple-access (OCDMA) and wavelength-division multiplexing (WDM) techniques in one system is a promising choice. OCDMA systems are getting more attractive as they provide the users with simultaneous and asynchronous access to the network with high security. OCDMA can also be overlaid onto the existing WDM networks in order to either expand the transmission capacity and/or to increase the level of security. In recent studies, hybrid OCDMA/WDM overlay systems have been proposed; where optical frequency hopping or spectral phase techniques with tunable delay lines have been used for coding. Some other researchers have focused on another category of hybrid WDM/OCDMA schemes, where codes of OCDMA can be employed on each WDM wavelength. However, these previous studies have not evaluated the performance as well as the security of hybrid conventional codes of the SAC-OCDMA/WDM overlay system. Besides that, the implementation of spectral-phase-coding and Wavelength-Hopping Time-Spreading (WHTS) codes for OCDMA systems are complex. In this thesis, the aim is to investigate the feasibility of transmitting both OCDMA and WDM signals on the same spectrum band, using Modified Quadratic Congruence (MQC) code as the signature code. In addition, the data confidentiality for OCDMA users under a hybrid scheme is also investigated. A new mathematical model is developed to describe the system which analyzes the system performance in terms of both the signal-to-noise and interference ratio (SNIR) and bit-error rate (BER). The multi-access interference (MAI) in addition to the phase-induced intensity noise (PIIN), shot noise, thermal noise, and in-band interference noise are also taken into consideration in the performance analysis. Furthermore, the proposed system was simulated using OptiSystem software V 9.0, and its performance in terms of both the BER and Q-factor were determined. Both hybrid and non-hybrid systems have been simulated, and the performance and confidentiality comparison has been presented and compared. The data confidentiality for OCDMA users under both conventional and hybrid approaches were evaluated using an eavesdropper's interceptor which is based on a simple energy detector, which is able to scan all corresponding SAC-OCDMA wavelengths to detect the entire coded signal of an authorized user. Hence, the eavesdropper probability of error-free code detection can be evaluated using simulation and some calculations. The results reveal that the hybrid transmission of both OCDMA and WDM signals on the same band gives an acceptable performance; the BER value is below 10-9 with security enhancement for OCDMA users, yet efficient use of the available spectral chip bandwidth of 20-40 GHz is achieved. It is also shown that the performance of the proposed system is limited by the interference of the WDM signals. In summary, the developed system is a feasible candidate for future optical access networks.,PhD
Pages:	119
Call Number:	TK5103.452 .A834 2013 3
Publisher:	UKM, Bangi
Appears in Collections:	Institute of Microengineering and Nanoelectronics / Institut Kejuruteraan Mikro dan Nanoelektronik (IMEN)

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