Free space optical communication in Indian cities; channel characteristics and link performance

Abstract Free Space Optical (FSO) communication systems, offering high-speed and high-bandwidth transmission, have emerged as a possible substitute for conventional wired and wireless communication systems. However, FSO links are susceptible to atmospheric deficiencies including attenuation, scintillation, and turbulence, which may severely impact the performance of the communication link. In this research paper, we propose and analyze the performance of a 25 Gbps dual-polarization quadrature phase shift keying (DP-QPSK) coherent optical orthogonal frequency division multiplexing (CO-OFDM)-based FSO communication link with spatial diversity technique under various climatic conditions in four different geographical locations of India, i.e., Delhi, Ahmedabad, Kolkata, and Chennai in the year 2021. The proposed FSO communication system is evaluated through performance analysis and parametric evaluation under various weather conditions such as clear sky, fog, haze, rain, cloud, and thermal gradient. Key performance metrics such as bit error rate (BER), Q-factor, signal-to-noise ratio (SNR), received power, communication range, and reliability are analyzed based on the simulation results. The proposed FSO communication system provides high data rates, improved power efficiency, better resilience to atmospheric impairments, reliable communication links under different weather conditions, and a practical solution for high-speed and high-bandwidth communication in various applications.