Development of OCDMA system based on Flexible Cross Correlation (FCC) code with OFDM modulation

• Improve the SAC–OCDMA system by using OFDM technique in order to provide more subcarriers which are orthogonal to each other. This will save the electrical bandwidth compare to subcarrier multiplexing which is not orthogonal. After that the signal sent in the optical code to be more secure.
• At the receiver the optical code distinguish by the filter and the signal will pass to demodulate OFDM. In demodulated OFDM specify each user by a few numbers of subcarriers, which in wireless part.
• Compare the proposed system by pervious subcarrier multiplexing OCDMA system.
• Using the Flexible Cross Correlation (FCC) code, which is proved in reference papers, as good code compare to MDW, MFH etc.
• The orthogonal subcarriers more robust of dispersion and improved the data rate of the system. Furthermore it increase the spectrum efficiency of the electrical signal, this save some power, and also serve more number of user.

The performance of the OCDMA systems is governed by numerous quantitative parameters such as the data rate, simultaneous number of users, the powers of transmitter and receiver, and the type of codes. This paper analyzes the performance of the OCDMA system using OFDM technique to enhance the channel data rate, to save power and increase the number of user of OSCDMA systems compared with previous hybrid subcarrier multiplexing/optical spectrum code division multiplexing (SCM/OSCDM) system. The average received signal to noise ratio (SNR) with the nonlinearity of subcarriers is derived. The theoretical results have been evaluated based on BER and number of users as well as amount of power saved. The proposed system gave better performance and save around −6 dBm of the power as well as increase the number of users twice compare to SCM/OCDMA system. In addition it is robust against interference and much more spectrally efficient than SCM/OCDMA system. The system was designed based on Flexible Cross Correlation (FCC) code which is easier construction, less complexity of encoder/decoder design and flexible in-phase cross-correlation for uncomplicated to implement using Fiber Bragg Gratings (FBGs) for the OCDMA systems for any number of users and weights. The OCDMA–FCC_OFDM improves the number of users (cardinality) 108% compare to SCM/ODCMA–FCC system.