120 Gbps FSO transmission system based on integrated OFDM-PDM-OCDMA transmission using ICSM code: performance analysis

A novel 120 Gbps free space optics (FSO) is presented in this paper based on integrating three multiplexing techniques, namely, orthogonal frequency division multiplexing (OFDM), polarization division multiplexing (PDM), and optical code division multiple access (OCDMA). For PDM, two states are utilized, each of which carries three different OCDMA channels assigned with distinct Identity Column Shift Matrix (ISCM) code sequences. A 20 Gbps of information is modulated by OFDM and transmitted on each channel. The impact of inclement weather conditions on the FSO channel is investigated, focusing on hazy, rainy, and foggy weather. The performance evaluation includes analyzing parameters such as the bit error rate (BER), maximum FSO range, received optical power (ROP), and the constellation diagram. Furthermore, the applicability of this model in practical settings is discussed for two distinct cities: Alexandria, Egypt, and Hyderabad, India; each is characterized by unique geographical locations and correspondingly diverse weather conditions. The simulation results assure that the information signal can propagate over longer ranges of 5.8 and 5 km when applied in Alexandria and in the presence of light haze (LH), respectively, with BER below \({10}^{-3}\) ${10}^{-3}$ and ROP \(\sim\) $\sim$ −11.8 dBm. In contrast, the lower range of 0.91 km occurs in the presence of heavy fog (HF) due to the large attenuation caused by this weather condition. Accordingly, the proposed 120 Gbps (2 polarization states; each has 3 channels, and each channel carries 20 Gbps of information) FSO model is suggested to be used in high-speed transmission networks.