In this paper, we investigate the impact of modulation index on the performances of SCM SAC-OCDMA system. Knowing that zero cross-correlation (ZCC) codes remove the effect of multiple access interference and of phase-induced intensity noise, SCM SAC-OCDM has been investigated using ZCC codes with two types of direct detection, one and all wavelengths of the code. In this hybrid system, the SNR depends on the modulation index for a given effective power of broadband source. In order to maximize the SNR, the optimum values of the modulation index, for different number of subcarriers, are determined analytically for two types of detection. The performance of the optimized system is evaluated based up on BER. The obtained numerical results show that, by optimizing the modulation index, the number of subcarriers (number of active users per ZCC code) is increased and the performance is significantly improved.

This paper proposes a novel method for constructing optical zero-correlation zone (OZCZ) codes based on the Mutually Orthogonal Complementary Sets (MOCS) matrix and the concatenation operation. The most important property of the obtained codes is that the periodic correlation function of the proposed codes is zero for the phase shifts within the zero-correlation zone. The procedure of construction is simple, flexible and offers increasing number of users \left( {M = {2^{n + 1}}} \right). In the other hand, we have presented a fully reconfigurable hardware implementation based on very high description language of the proposed OZCZ codes for optical code-division multiple-access encoder system. The implementation is performed on an Altera field-programmable gate arrays device using ROM memory and an up counter. The simulation results have been found satisfactory and are in conformity with the theoretical observations.

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The physical layer of an optical network is vulnerable towards various types of security threats such as physical infrastructure attacks and eavesdropping, where the security item requires more attention in front of the dramatically grows in network capacity. In this paper, authors propose a comparison in performance of zero correlation zone-Optical Code Division Multiple Access based on different confidentiality mechanisms implemented using existing optical logic components such as line selectors, wavelength convertors and XOR gates. The performance of the proposed designs in terms of log of the bit error rate (BER) as function of the received power was evaluated through OptiSystem software simulation. The achieved results demonstrate that design 3 is the best confidentiality solution in terms of received power, BER performance and architecture complexity.

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