الخلاصة:
In this thesis, we are interested in the study of a new techniques and approaches for optical communications and quantum encryption. In first time, we describe the various optical communications technology particularly that used in multiple access systems (Optical Code Division Multiplexing Access). In the same context, we detailed the different codes proposed in the literature for this type of access technique, including the steps required to generate 2D and 1D code types. The second part is devoted to the study of the concept of generalized quantum walks for WDM applications (Wavelength Division Multiplexing). Starting with the establishment of the state of the art for this type of quantum encryption, and then presents some models studied in the last decades. The third part is divided into two parts. Firstly, we
propose a new family code for the SAC-OCDMA system. Since the concept of the code is
based on the flexible cross-correlation (FCC), is called the 'Modified Flexible Cross
Correlation ' (MFCC). The OCDMA system performance with the proposed code MFCC is
analyzed taking into account the effect of shot noise, noise PIIN and thermal noise. It is noted that the MFCC code is the best in terms of BER compared to MDW and RD codes. Its simplicity in the building code and flexibility in the cross-correlation control makes this code a suitable candidate for future OCDMA systems. Secondly, we study the ability of quantum networks to support both random and non-random data signals over a shared infrastructure.
The effect of the wavelength on the coverage distance with the quantum bit error rate of a QKD system is analyzed. The results of the random phase showed a minimum distance to cover compared with the non-random phase. For the random emission amplitude fluctuation improvement in system performance is achieved. Therefore, we find that the few changes should not degrade significantly the performance of the system, but the mode of sending the data has a significant effect on the channel integrity.
