FSO-CDMA system performance enhancement based on new hybrid code and M-ary digital pulse position modulation technique

摘要

Abstract In this paper, the performance efficiency of the free‐space optical (FSO) communication link has been enhanced using a new hybrid prime code (NHPC) and M‐ary digital pulse position modulation (M‐ary DPPM) technique. The passive optical network (PON) optical code division multiple access (OCDMA) technique based on the FSO link is proposed. The analysis and optimization of the bit error rate (BER) performance of the Gaussian approximation techniques are investigated in the existence of both an atmospheric turbulence (AT) channels and multiple access interference (MAI). Additionally, 76 NHPC orthogonal sequences have been transmitted at a data rate of 10 Gbps over a turbulent FSO channel. In the proposed design, the NHPC M‐ary DPPM modulation is used to provide extra bits of information to enhance the system performance. Also, the adaptive optics technique to mitigate the AT effect and improve the modulation efficiency is offered in this design. Further, the impact of the turbulence effect on the proposed system performance based on NHPC-M ary-DPPM modulation as a function of M‐ary DPPM parameters and other atmospheric parameters is investigated. The NHPC M‐ary DPPM provides an optical signal‐to‐noise ratio (OSNR) of about 2–4 dB for the strong turbulence at a target BER of 10−9. Additionally, the proposed system performance is compared with another system that uses the on–off keying-DPPM (OOK-M ary- DPPM). The numerical results indicate that the proposed design can be enhanced with the NHPC M-ary DPPM for FSO-OCDMA systems and the OSNR can be increased 14–18 dB at a BER of 10−9 in comparison to other approaches. The simulation results show that the proposed modulation technique can be used in the FSO-OCDMA systems, having a significant increase in their efficiency. Finally, the use of the NHPC M‐ary DPPM modulation schemes is a new technique that is used to reduce the AT, interchannel crosstalk and the MAI noise for the FSO-OCDMA systems.