Performance Analysis of a DPSK-based High-Speed Spectral-Efficient FSO System under Different Weather Conditions

The Free-Space Optical (FSO) communication system has proven its capability to enhance spectral efficiency and support high data rates owing to its large available bandwidth compared to other communication techniques. However, the FSO-transmission link is highly sensitive to dynamic conditions such as atmospheric turbulence and weather conditions, therefore, channel attenuation arises and the received optical signal is degraded and distorted at the receiver end. In this paper, Dense Wavelength Division Multiplexing (DWDM) based (40 H 10) Gb/s FSO system performance is demonstrated over a maximum transmission link of 50-70 km with quality factor of Q = 16-4 in clear sky, condition whereas it is 0.1 km to 4 km in fog to rain weather conditions for the BER range of 10-9 to 10-;. The novelty in this work is to achieve the optimum link distance with acceptable BER using a spectrally efficient (DWDM channel spacing of 0.6 nm), high speed advanced NRZ-DPSK (10 Gb/s) modulation format under very dense fog and rain weather conditions. Furthermore, an EDFA pre-amplifier with a gain of 20 dB has been incorporated at the transmitter side to mitigate the impact of atmospheric attenuation to achieve maximum transmission range of 70 km in clear sky conditions.