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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 and ROP ∼ −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. [ABSTRACT FROM AUTHOR]

A novel free space optics (FSO) communication system based on integration of two different multiplexing techniques i.e., orbital angular momentum (OAM) multiplexing and optical code division multiple access (OCDMA), are proposed in this paper for enhancing the transmission capacity. Four distinct OAM beams are used; each transporting 10 Gbps information of three different OCDMA channels. These channels are assigned with diagonal permutation shift (DPS) code. Various atmospheric conditions are considered in evaluating the performance of our suggested design in FSO communication system. These weather conditions are snowy and dusty in addition to the average intensity rainfall rates in Saudi Arabia cities (Riyadh and Jeddah) and Indian cities (Hyderabad, Pune, Chennai, and Mumbai). Received optical power (ROP), Quality (Q) factor, maximum FSO link range, and eye diagrams are used for evaluating the performance. The simulation results show successful transmission of 4 OAM × 3 OCDMA channels × 10 Gbps = 120 Gbps overall capacity with good ROP, Q-factor, and BER values. The maximum FSO link range achieved is 600 m under wet snow (WS), 140 m under dry snow (DS), and 400, 132, and 52 m, respectively, under low dust (LD), medium dust (MD), and heavy dust (HD) storms. Consequently, this proposed FSO transmission model is suggested to be used as high-speed connectivity for end users in adverse weather conditions. [ABSTRACT FROM AUTHOR]

Free space optical communication (FSOC) has emerged as a potential candidate for providing huge bandwidth and solving the problem of spectrum congestion. But the atmospheric conditions limit the performance of FSOC link as the laser signal propagates through the atmospheric channel. This work aims to investigate the performance of FSOC link under average and heavy rainfall weather conditions of India. The meteorological data related to rainfall, over a duration of 4 years, was obtained from the Indian Meteorological Department for six different locations of India, representing the inland and coastal areas. The attenuation coefficient due to rain for all the locations has been calculated using mathematical models. The performance analysis of Wavelength Division Multiplexing based free space optical communication system has been analyzed by incorporating the attenuation due to rain for all considered locations. The inland location of Hyderabad has recorded the minimum attenuation coefficient of 1.91 dB/km due to rain and can support a link range of 5.43 km, corresponding to bit error rate of order of 10−9 under average rain weather conditions. On the other hand, the average rainfall is maximum for the coastal area of Mumbai, resulting in maximum attenuation coefficient of 4.08 dB/km. Moreover, the maximum link range for Mumbai is limited to 3.48 km, corresponding to bit error rate of order of 10–9 under average conditions of rain weather. Similarly, the inland locations of India have delivered a better link performance as compared to coastal areas under heavy rainfall weather conditions also. [ABSTRACT FROM AUTHOR]